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TOMOYO Linux Cross Reference
Linux/kernel/signal.c

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  1 /*
  2  *  linux/kernel/signal.c
  3  *
  4  *  Copyright (C) 1991, 1992  Linus Torvalds
  5  *
  6  *  1997-11-02  Modified for POSIX.1b signals by Richard Henderson
  7  *
  8  *  2003-06-02  Jim Houston - Concurrent Computer Corp.
  9  *              Changes to use preallocated sigqueue structures
 10  *              to allow signals to be sent reliably.
 11  */
 12 
 13 #include <linux/slab.h>
 14 #include <linux/export.h>
 15 #include <linux/init.h>
 16 #include <linux/sched/mm.h>
 17 #include <linux/sched/user.h>
 18 #include <linux/sched/debug.h>
 19 #include <linux/sched/task.h>
 20 #include <linux/sched/task_stack.h>
 21 #include <linux/sched/cputime.h>
 22 #include <linux/fs.h>
 23 #include <linux/tty.h>
 24 #include <linux/binfmts.h>
 25 #include <linux/coredump.h>
 26 #include <linux/security.h>
 27 #include <linux/syscalls.h>
 28 #include <linux/ptrace.h>
 29 #include <linux/signal.h>
 30 #include <linux/signalfd.h>
 31 #include <linux/ratelimit.h>
 32 #include <linux/tracehook.h>
 33 #include <linux/capability.h>
 34 #include <linux/freezer.h>
 35 #include <linux/pid_namespace.h>
 36 #include <linux/nsproxy.h>
 37 #include <linux/user_namespace.h>
 38 #include <linux/uprobes.h>
 39 #include <linux/compat.h>
 40 #include <linux/cn_proc.h>
 41 #include <linux/compiler.h>
 42 
 43 #define CREATE_TRACE_POINTS
 44 #include <trace/events/signal.h>
 45 
 46 #include <asm/param.h>
 47 #include <linux/uaccess.h>
 48 #include <asm/unistd.h>
 49 #include <asm/siginfo.h>
 50 #include <asm/cacheflush.h>
 51 #include "audit.h"      /* audit_signal_info() */
 52 
 53 /*
 54  * SLAB caches for signal bits.
 55  */
 56 
 57 static struct kmem_cache *sigqueue_cachep;
 58 
 59 int print_fatal_signals __read_mostly;
 60 
 61 static void __user *sig_handler(struct task_struct *t, int sig)
 62 {
 63         return t->sighand->action[sig - 1].sa.sa_handler;
 64 }
 65 
 66 static int sig_handler_ignored(void __user *handler, int sig)
 67 {
 68         /* Is it explicitly or implicitly ignored? */
 69         return handler == SIG_IGN ||
 70                 (handler == SIG_DFL && sig_kernel_ignore(sig));
 71 }
 72 
 73 static int sig_task_ignored(struct task_struct *t, int sig, bool force)
 74 {
 75         void __user *handler;
 76 
 77         handler = sig_handler(t, sig);
 78 
 79         if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
 80                         handler == SIG_DFL && !force)
 81                 return 1;
 82 
 83         return sig_handler_ignored(handler, sig);
 84 }
 85 
 86 static int sig_ignored(struct task_struct *t, int sig, bool force)
 87 {
 88         /*
 89          * Blocked signals are never ignored, since the
 90          * signal handler may change by the time it is
 91          * unblocked.
 92          */
 93         if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
 94                 return 0;
 95 
 96         if (!sig_task_ignored(t, sig, force))
 97                 return 0;
 98 
 99         /*
100          * Tracers may want to know about even ignored signals.
101          */
102         return !t->ptrace;
103 }
104 
105 /*
106  * Re-calculate pending state from the set of locally pending
107  * signals, globally pending signals, and blocked signals.
108  */
109 static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
110 {
111         unsigned long ready;
112         long i;
113 
114         switch (_NSIG_WORDS) {
115         default:
116                 for (i = _NSIG_WORDS, ready = 0; --i >= 0 ;)
117                         ready |= signal->sig[i] &~ blocked->sig[i];
118                 break;
119 
120         case 4: ready  = signal->sig[3] &~ blocked->sig[3];
121                 ready |= signal->sig[2] &~ blocked->sig[2];
122                 ready |= signal->sig[1] &~ blocked->sig[1];
123                 ready |= signal->sig[0] &~ blocked->sig[0];
124                 break;
125 
126         case 2: ready  = signal->sig[1] &~ blocked->sig[1];
127                 ready |= signal->sig[0] &~ blocked->sig[0];
128                 break;
129 
130         case 1: ready  = signal->sig[0] &~ blocked->sig[0];
131         }
132         return ready != 0;
133 }
134 
135 #define PENDING(p,b) has_pending_signals(&(p)->signal, (b))
136 
137 static int recalc_sigpending_tsk(struct task_struct *t)
138 {
139         if ((t->jobctl & JOBCTL_PENDING_MASK) ||
140             PENDING(&t->pending, &t->blocked) ||
141             PENDING(&t->signal->shared_pending, &t->blocked)) {
142                 set_tsk_thread_flag(t, TIF_SIGPENDING);
143                 return 1;
144         }
145         /*
146          * We must never clear the flag in another thread, or in current
147          * when it's possible the current syscall is returning -ERESTART*.
148          * So we don't clear it here, and only callers who know they should do.
149          */
150         return 0;
151 }
152 
153 /*
154  * After recalculating TIF_SIGPENDING, we need to make sure the task wakes up.
155  * This is superfluous when called on current, the wakeup is a harmless no-op.
156  */
157 void recalc_sigpending_and_wake(struct task_struct *t)
158 {
159         if (recalc_sigpending_tsk(t))
160                 signal_wake_up(t, 0);
161 }
162 
163 void recalc_sigpending(void)
164 {
165         if (!recalc_sigpending_tsk(current) && !freezing(current))
166                 clear_thread_flag(TIF_SIGPENDING);
167 
168 }
169 
170 /* Given the mask, find the first available signal that should be serviced. */
171 
172 #define SYNCHRONOUS_MASK \
173         (sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \
174          sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS))
175 
176 int next_signal(struct sigpending *pending, sigset_t *mask)
177 {
178         unsigned long i, *s, *m, x;
179         int sig = 0;
180 
181         s = pending->signal.sig;
182         m = mask->sig;
183 
184         /*
185          * Handle the first word specially: it contains the
186          * synchronous signals that need to be dequeued first.
187          */
188         x = *s &~ *m;
189         if (x) {
190                 if (x & SYNCHRONOUS_MASK)
191                         x &= SYNCHRONOUS_MASK;
192                 sig = ffz(~x) + 1;
193                 return sig;
194         }
195 
196         switch (_NSIG_WORDS) {
197         default:
198                 for (i = 1; i < _NSIG_WORDS; ++i) {
199                         x = *++s &~ *++m;
200                         if (!x)
201                                 continue;
202                         sig = ffz(~x) + i*_NSIG_BPW + 1;
203                         break;
204                 }
205                 break;
206 
207         case 2:
208                 x = s[1] &~ m[1];
209                 if (!x)
210                         break;
211                 sig = ffz(~x) + _NSIG_BPW + 1;
212                 break;
213 
214         case 1:
215                 /* Nothing to do */
216                 break;
217         }
218 
219         return sig;
220 }
221 
222 static inline void print_dropped_signal(int sig)
223 {
224         static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
225 
226         if (!print_fatal_signals)
227                 return;
228 
229         if (!__ratelimit(&ratelimit_state))
230                 return;
231 
232         pr_info("%s/%d: reached RLIMIT_SIGPENDING, dropped signal %d\n",
233                                 current->comm, current->pid, sig);
234 }
235 
236 /**
237  * task_set_jobctl_pending - set jobctl pending bits
238  * @task: target task
239  * @mask: pending bits to set
240  *
241  * Clear @mask from @task->jobctl.  @mask must be subset of
242  * %JOBCTL_PENDING_MASK | %JOBCTL_STOP_CONSUME | %JOBCTL_STOP_SIGMASK |
243  * %JOBCTL_TRAPPING.  If stop signo is being set, the existing signo is
244  * cleared.  If @task is already being killed or exiting, this function
245  * becomes noop.
246  *
247  * CONTEXT:
248  * Must be called with @task->sighand->siglock held.
249  *
250  * RETURNS:
251  * %true if @mask is set, %false if made noop because @task was dying.
252  */
253 bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask)
254 {
255         BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME |
256                         JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING));
257         BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK));
258 
259         if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING)))
260                 return false;
261 
262         if (mask & JOBCTL_STOP_SIGMASK)
263                 task->jobctl &= ~JOBCTL_STOP_SIGMASK;
264 
265         task->jobctl |= mask;
266         return true;
267 }
268 
269 /**
270  * task_clear_jobctl_trapping - clear jobctl trapping bit
271  * @task: target task
272  *
273  * If JOBCTL_TRAPPING is set, a ptracer is waiting for us to enter TRACED.
274  * Clear it and wake up the ptracer.  Note that we don't need any further
275  * locking.  @task->siglock guarantees that @task->parent points to the
276  * ptracer.
277  *
278  * CONTEXT:
279  * Must be called with @task->sighand->siglock held.
280  */
281 void task_clear_jobctl_trapping(struct task_struct *task)
282 {
283         if (unlikely(task->jobctl & JOBCTL_TRAPPING)) {
284                 task->jobctl &= ~JOBCTL_TRAPPING;
285                 smp_mb();       /* advised by wake_up_bit() */
286                 wake_up_bit(&task->jobctl, JOBCTL_TRAPPING_BIT);
287         }
288 }
289 
290 /**
291  * task_clear_jobctl_pending - clear jobctl pending bits
292  * @task: target task
293  * @mask: pending bits to clear
294  *
295  * Clear @mask from @task->jobctl.  @mask must be subset of
296  * %JOBCTL_PENDING_MASK.  If %JOBCTL_STOP_PENDING is being cleared, other
297  * STOP bits are cleared together.
298  *
299  * If clearing of @mask leaves no stop or trap pending, this function calls
300  * task_clear_jobctl_trapping().
301  *
302  * CONTEXT:
303  * Must be called with @task->sighand->siglock held.
304  */
305 void task_clear_jobctl_pending(struct task_struct *task, unsigned long mask)
306 {
307         BUG_ON(mask & ~JOBCTL_PENDING_MASK);
308 
309         if (mask & JOBCTL_STOP_PENDING)
310                 mask |= JOBCTL_STOP_CONSUME | JOBCTL_STOP_DEQUEUED;
311 
312         task->jobctl &= ~mask;
313 
314         if (!(task->jobctl & JOBCTL_PENDING_MASK))
315                 task_clear_jobctl_trapping(task);
316 }
317 
318 /**
319  * task_participate_group_stop - participate in a group stop
320  * @task: task participating in a group stop
321  *
322  * @task has %JOBCTL_STOP_PENDING set and is participating in a group stop.
323  * Group stop states are cleared and the group stop count is consumed if
324  * %JOBCTL_STOP_CONSUME was set.  If the consumption completes the group
325  * stop, the appropriate %SIGNAL_* flags are set.
326  *
327  * CONTEXT:
328  * Must be called with @task->sighand->siglock held.
329  *
330  * RETURNS:
331  * %true if group stop completion should be notified to the parent, %false
332  * otherwise.
333  */
334 static bool task_participate_group_stop(struct task_struct *task)
335 {
336         struct signal_struct *sig = task->signal;
337         bool consume = task->jobctl & JOBCTL_STOP_CONSUME;
338 
339         WARN_ON_ONCE(!(task->jobctl & JOBCTL_STOP_PENDING));
340 
341         task_clear_jobctl_pending(task, JOBCTL_STOP_PENDING);
342 
343         if (!consume)
344                 return false;
345 
346         if (!WARN_ON_ONCE(sig->group_stop_count == 0))
347                 sig->group_stop_count--;
348 
349         /*
350          * Tell the caller to notify completion iff we are entering into a
351          * fresh group stop.  Read comment in do_signal_stop() for details.
352          */
353         if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) {
354                 signal_set_stop_flags(sig, SIGNAL_STOP_STOPPED);
355                 return true;
356         }
357         return false;
358 }
359 
360 /*
361  * allocate a new signal queue record
362  * - this may be called without locks if and only if t == current, otherwise an
363  *   appropriate lock must be held to stop the target task from exiting
364  */
365 static struct sigqueue *
366 __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
367 {
368         struct sigqueue *q = NULL;
369         struct user_struct *user;
370 
371         /*
372          * Protect access to @t credentials. This can go away when all
373          * callers hold rcu read lock.
374          */
375         rcu_read_lock();
376         user = get_uid(__task_cred(t)->user);
377         atomic_inc(&user->sigpending);
378         rcu_read_unlock();
379 
380         if (override_rlimit ||
381             atomic_read(&user->sigpending) <=
382                         task_rlimit(t, RLIMIT_SIGPENDING)) {
383                 q = kmem_cache_alloc(sigqueue_cachep, flags);
384         } else {
385                 print_dropped_signal(sig);
386         }
387 
388         if (unlikely(q == NULL)) {
389                 atomic_dec(&user->sigpending);
390                 free_uid(user);
391         } else {
392                 INIT_LIST_HEAD(&q->list);
393                 q->flags = 0;
394                 q->user = user;
395         }
396 
397         return q;
398 }
399 
400 static void __sigqueue_free(struct sigqueue *q)
401 {
402         if (q->flags & SIGQUEUE_PREALLOC)
403                 return;
404         atomic_dec(&q->user->sigpending);
405         free_uid(q->user);
406         kmem_cache_free(sigqueue_cachep, q);
407 }
408 
409 void flush_sigqueue(struct sigpending *queue)
410 {
411         struct sigqueue *q;
412 
413         sigemptyset(&queue->signal);
414         while (!list_empty(&queue->list)) {
415                 q = list_entry(queue->list.next, struct sigqueue , list);
416                 list_del_init(&q->list);
417                 __sigqueue_free(q);
418         }
419 }
420 
421 /*
422  * Flush all pending signals for this kthread.
423  */
424 void flush_signals(struct task_struct *t)
425 {
426         unsigned long flags;
427 
428         spin_lock_irqsave(&t->sighand->siglock, flags);
429         clear_tsk_thread_flag(t, TIF_SIGPENDING);
430         flush_sigqueue(&t->pending);
431         flush_sigqueue(&t->signal->shared_pending);
432         spin_unlock_irqrestore(&t->sighand->siglock, flags);
433 }
434 
435 #ifdef CONFIG_POSIX_TIMERS
436 static void __flush_itimer_signals(struct sigpending *pending)
437 {
438         sigset_t signal, retain;
439         struct sigqueue *q, *n;
440 
441         signal = pending->signal;
442         sigemptyset(&retain);
443 
444         list_for_each_entry_safe(q, n, &pending->list, list) {
445                 int sig = q->info.si_signo;
446 
447                 if (likely(q->info.si_code != SI_TIMER)) {
448                         sigaddset(&retain, sig);
449                 } else {
450                         sigdelset(&signal, sig);
451                         list_del_init(&q->list);
452                         __sigqueue_free(q);
453                 }
454         }
455 
456         sigorsets(&pending->signal, &signal, &retain);
457 }
458 
459 void flush_itimer_signals(void)
460 {
461         struct task_struct *tsk = current;
462         unsigned long flags;
463 
464         spin_lock_irqsave(&tsk->sighand->siglock, flags);
465         __flush_itimer_signals(&tsk->pending);
466         __flush_itimer_signals(&tsk->signal->shared_pending);
467         spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
468 }
469 #endif
470 
471 void ignore_signals(struct task_struct *t)
472 {
473         int i;
474 
475         for (i = 0; i < _NSIG; ++i)
476                 t->sighand->action[i].sa.sa_handler = SIG_IGN;
477 
478         flush_signals(t);
479 }
480 
481 /*
482  * Flush all handlers for a task.
483  */
484 
485 void
486 flush_signal_handlers(struct task_struct *t, int force_default)
487 {
488         int i;
489         struct k_sigaction *ka = &t->sighand->action[0];
490         for (i = _NSIG ; i != 0 ; i--) {
491                 if (force_default || ka->sa.sa_handler != SIG_IGN)
492                         ka->sa.sa_handler = SIG_DFL;
493                 ka->sa.sa_flags = 0;
494 #ifdef __ARCH_HAS_SA_RESTORER
495                 ka->sa.sa_restorer = NULL;
496 #endif
497                 sigemptyset(&ka->sa.sa_mask);
498                 ka++;
499         }
500 }
501 
502 int unhandled_signal(struct task_struct *tsk, int sig)
503 {
504         void __user *handler = tsk->sighand->action[sig-1].sa.sa_handler;
505         if (is_global_init(tsk))
506                 return 1;
507         if (handler != SIG_IGN && handler != SIG_DFL)
508                 return 0;
509         /* if ptraced, let the tracer determine */
510         return !tsk->ptrace;
511 }
512 
513 static void collect_signal(int sig, struct sigpending *list, siginfo_t *info,
514                            bool *resched_timer)
515 {
516         struct sigqueue *q, *first = NULL;
517 
518         /*
519          * Collect the siginfo appropriate to this signal.  Check if
520          * there is another siginfo for the same signal.
521         */
522         list_for_each_entry(q, &list->list, list) {
523                 if (q->info.si_signo == sig) {
524                         if (first)
525                                 goto still_pending;
526                         first = q;
527                 }
528         }
529 
530         sigdelset(&list->signal, sig);
531 
532         if (first) {
533 still_pending:
534                 list_del_init(&first->list);
535                 copy_siginfo(info, &first->info);
536 
537                 *resched_timer =
538                         (first->flags & SIGQUEUE_PREALLOC) &&
539                         (info->si_code == SI_TIMER) &&
540                         (info->si_sys_private);
541 
542                 __sigqueue_free(first);
543         } else {
544                 /*
545                  * Ok, it wasn't in the queue.  This must be
546                  * a fast-pathed signal or we must have been
547                  * out of queue space.  So zero out the info.
548                  */
549                 info->si_signo = sig;
550                 info->si_errno = 0;
551                 info->si_code = SI_USER;
552                 info->si_pid = 0;
553                 info->si_uid = 0;
554         }
555 }
556 
557 static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
558                         siginfo_t *info, bool *resched_timer)
559 {
560         int sig = next_signal(pending, mask);
561 
562         if (sig)
563                 collect_signal(sig, pending, info, resched_timer);
564         return sig;
565 }
566 
567 /*
568  * Dequeue a signal and return the element to the caller, which is
569  * expected to free it.
570  *
571  * All callers have to hold the siglock.
572  */
573 int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
574 {
575         bool resched_timer = false;
576         int signr;
577 
578         /* We only dequeue private signals from ourselves, we don't let
579          * signalfd steal them
580          */
581         signr = __dequeue_signal(&tsk->pending, mask, info, &resched_timer);
582         if (!signr) {
583                 signr = __dequeue_signal(&tsk->signal->shared_pending,
584                                          mask, info, &resched_timer);
585 #ifdef CONFIG_POSIX_TIMERS
586                 /*
587                  * itimer signal ?
588                  *
589                  * itimers are process shared and we restart periodic
590                  * itimers in the signal delivery path to prevent DoS
591                  * attacks in the high resolution timer case. This is
592                  * compliant with the old way of self-restarting
593                  * itimers, as the SIGALRM is a legacy signal and only
594                  * queued once. Changing the restart behaviour to
595                  * restart the timer in the signal dequeue path is
596                  * reducing the timer noise on heavy loaded !highres
597                  * systems too.
598                  */
599                 if (unlikely(signr == SIGALRM)) {
600                         struct hrtimer *tmr = &tsk->signal->real_timer;
601 
602                         if (!hrtimer_is_queued(tmr) &&
603                             tsk->signal->it_real_incr != 0) {
604                                 hrtimer_forward(tmr, tmr->base->get_time(),
605                                                 tsk->signal->it_real_incr);
606                                 hrtimer_restart(tmr);
607                         }
608                 }
609 #endif
610         }
611 
612         recalc_sigpending();
613         if (!signr)
614                 return 0;
615 
616         if (unlikely(sig_kernel_stop(signr))) {
617                 /*
618                  * Set a marker that we have dequeued a stop signal.  Our
619                  * caller might release the siglock and then the pending
620                  * stop signal it is about to process is no longer in the
621                  * pending bitmasks, but must still be cleared by a SIGCONT
622                  * (and overruled by a SIGKILL).  So those cases clear this
623                  * shared flag after we've set it.  Note that this flag may
624                  * remain set after the signal we return is ignored or
625                  * handled.  That doesn't matter because its only purpose
626                  * is to alert stop-signal processing code when another
627                  * processor has come along and cleared the flag.
628                  */
629                 current->jobctl |= JOBCTL_STOP_DEQUEUED;
630         }
631 #ifdef CONFIG_POSIX_TIMERS
632         if (resched_timer) {
633                 /*
634                  * Release the siglock to ensure proper locking order
635                  * of timer locks outside of siglocks.  Note, we leave
636                  * irqs disabled here, since the posix-timers code is
637                  * about to disable them again anyway.
638                  */
639                 spin_unlock(&tsk->sighand->siglock);
640                 do_schedule_next_timer(info);
641                 spin_lock(&tsk->sighand->siglock);
642         }
643 #endif
644         return signr;
645 }
646 
647 /*
648  * Tell a process that it has a new active signal..
649  *
650  * NOTE! we rely on the previous spin_lock to
651  * lock interrupts for us! We can only be called with
652  * "siglock" held, and the local interrupt must
653  * have been disabled when that got acquired!
654  *
655  * No need to set need_resched since signal event passing
656  * goes through ->blocked
657  */
658 void signal_wake_up_state(struct task_struct *t, unsigned int state)
659 {
660         set_tsk_thread_flag(t, TIF_SIGPENDING);
661         /*
662          * TASK_WAKEKILL also means wake it up in the stopped/traced/killable
663          * case. We don't check t->state here because there is a race with it
664          * executing another processor and just now entering stopped state.
665          * By using wake_up_state, we ensure the process will wake up and
666          * handle its death signal.
667          */
668         if (!wake_up_state(t, state | TASK_INTERRUPTIBLE))
669                 kick_process(t);
670 }
671 
672 /*
673  * Remove signals in mask from the pending set and queue.
674  * Returns 1 if any signals were found.
675  *
676  * All callers must be holding the siglock.
677  */
678 static int flush_sigqueue_mask(sigset_t *mask, struct sigpending *s)
679 {
680         struct sigqueue *q, *n;
681         sigset_t m;
682 
683         sigandsets(&m, mask, &s->signal);
684         if (sigisemptyset(&m))
685                 return 0;
686 
687         sigandnsets(&s->signal, &s->signal, mask);
688         list_for_each_entry_safe(q, n, &s->list, list) {
689                 if (sigismember(mask, q->info.si_signo)) {
690                         list_del_init(&q->list);
691                         __sigqueue_free(q);
692                 }
693         }
694         return 1;
695 }
696 
697 static inline int is_si_special(const struct siginfo *info)
698 {
699         return info <= SEND_SIG_FORCED;
700 }
701 
702 static inline bool si_fromuser(const struct siginfo *info)
703 {
704         return info == SEND_SIG_NOINFO ||
705                 (!is_si_special(info) && SI_FROMUSER(info));
706 }
707 
708 /*
709  * called with RCU read lock from check_kill_permission()
710  */
711 static int kill_ok_by_cred(struct task_struct *t)
712 {
713         const struct cred *cred = current_cred();
714         const struct cred *tcred = __task_cred(t);
715 
716         if (uid_eq(cred->euid, tcred->suid) ||
717             uid_eq(cred->euid, tcred->uid)  ||
718             uid_eq(cred->uid,  tcred->suid) ||
719             uid_eq(cred->uid,  tcred->uid))
720                 return 1;
721 
722         if (ns_capable(tcred->user_ns, CAP_KILL))
723                 return 1;
724 
725         return 0;
726 }
727 
728 /*
729  * Bad permissions for sending the signal
730  * - the caller must hold the RCU read lock
731  */
732 static int check_kill_permission(int sig, struct siginfo *info,
733                                  struct task_struct *t)
734 {
735         struct pid *sid;
736         int error;
737 
738         if (!valid_signal(sig))
739                 return -EINVAL;
740 
741         if (!si_fromuser(info))
742                 return 0;
743 
744         error = audit_signal_info(sig, t); /* Let audit system see the signal */
745         if (error)
746                 return error;
747 
748         if (!same_thread_group(current, t) &&
749             !kill_ok_by_cred(t)) {
750                 switch (sig) {
751                 case SIGCONT:
752                         sid = task_session(t);
753                         /*
754                          * We don't return the error if sid == NULL. The
755                          * task was unhashed, the caller must notice this.
756                          */
757                         if (!sid || sid == task_session(current))
758                                 break;
759                 default:
760                         return -EPERM;
761                 }
762         }
763 
764         return security_task_kill(t, info, sig, 0);
765 }
766 
767 /**
768  * ptrace_trap_notify - schedule trap to notify ptracer
769  * @t: tracee wanting to notify tracer
770  *
771  * This function schedules sticky ptrace trap which is cleared on the next
772  * TRAP_STOP to notify ptracer of an event.  @t must have been seized by
773  * ptracer.
774  *
775  * If @t is running, STOP trap will be taken.  If trapped for STOP and
776  * ptracer is listening for events, tracee is woken up so that it can
777  * re-trap for the new event.  If trapped otherwise, STOP trap will be
778  * eventually taken without returning to userland after the existing traps
779  * are finished by PTRACE_CONT.
780  *
781  * CONTEXT:
782  * Must be called with @task->sighand->siglock held.
783  */
784 static void ptrace_trap_notify(struct task_struct *t)
785 {
786         WARN_ON_ONCE(!(t->ptrace & PT_SEIZED));
787         assert_spin_locked(&t->sighand->siglock);
788 
789         task_set_jobctl_pending(t, JOBCTL_TRAP_NOTIFY);
790         ptrace_signal_wake_up(t, t->jobctl & JOBCTL_LISTENING);
791 }
792 
793 /*
794  * Handle magic process-wide effects of stop/continue signals. Unlike
795  * the signal actions, these happen immediately at signal-generation
796  * time regardless of blocking, ignoring, or handling.  This does the
797  * actual continuing for SIGCONT, but not the actual stopping for stop
798  * signals. The process stop is done as a signal action for SIG_DFL.
799  *
800  * Returns true if the signal should be actually delivered, otherwise
801  * it should be dropped.
802  */
803 static bool prepare_signal(int sig, struct task_struct *p, bool force)
804 {
805         struct signal_struct *signal = p->signal;
806         struct task_struct *t;
807         sigset_t flush;
808 
809         if (signal->flags & (SIGNAL_GROUP_EXIT | SIGNAL_GROUP_COREDUMP)) {
810                 if (!(signal->flags & SIGNAL_GROUP_EXIT))
811                         return sig == SIGKILL;
812                 /*
813                  * The process is in the middle of dying, nothing to do.
814                  */
815         } else if (sig_kernel_stop(sig)) {
816                 /*
817                  * This is a stop signal.  Remove SIGCONT from all queues.
818                  */
819                 siginitset(&flush, sigmask(SIGCONT));
820                 flush_sigqueue_mask(&flush, &signal->shared_pending);
821                 for_each_thread(p, t)
822                         flush_sigqueue_mask(&flush, &t->pending);
823         } else if (sig == SIGCONT) {
824                 unsigned int why;
825                 /*
826                  * Remove all stop signals from all queues, wake all threads.
827                  */
828                 siginitset(&flush, SIG_KERNEL_STOP_MASK);
829                 flush_sigqueue_mask(&flush, &signal->shared_pending);
830                 for_each_thread(p, t) {
831                         flush_sigqueue_mask(&flush, &t->pending);
832                         task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING);
833                         if (likely(!(t->ptrace & PT_SEIZED)))
834                                 wake_up_state(t, __TASK_STOPPED);
835                         else
836                                 ptrace_trap_notify(t);
837                 }
838 
839                 /*
840                  * Notify the parent with CLD_CONTINUED if we were stopped.
841                  *
842                  * If we were in the middle of a group stop, we pretend it
843                  * was already finished, and then continued. Since SIGCHLD
844                  * doesn't queue we report only CLD_STOPPED, as if the next
845                  * CLD_CONTINUED was dropped.
846                  */
847                 why = 0;
848                 if (signal->flags & SIGNAL_STOP_STOPPED)
849                         why |= SIGNAL_CLD_CONTINUED;
850                 else if (signal->group_stop_count)
851                         why |= SIGNAL_CLD_STOPPED;
852 
853                 if (why) {
854                         /*
855                          * The first thread which returns from do_signal_stop()
856                          * will take ->siglock, notice SIGNAL_CLD_MASK, and
857                          * notify its parent. See get_signal_to_deliver().
858                          */
859                         signal_set_stop_flags(signal, why | SIGNAL_STOP_CONTINUED);
860                         signal->group_stop_count = 0;
861                         signal->group_exit_code = 0;
862                 }
863         }
864 
865         return !sig_ignored(p, sig, force);
866 }
867 
868 /*
869  * Test if P wants to take SIG.  After we've checked all threads with this,
870  * it's equivalent to finding no threads not blocking SIG.  Any threads not
871  * blocking SIG were ruled out because they are not running and already
872  * have pending signals.  Such threads will dequeue from the shared queue
873  * as soon as they're available, so putting the signal on the shared queue
874  * will be equivalent to sending it to one such thread.
875  */
876 static inline int wants_signal(int sig, struct task_struct *p)
877 {
878         if (sigismember(&p->blocked, sig))
879                 return 0;
880         if (p->flags & PF_EXITING)
881                 return 0;
882         if (sig == SIGKILL)
883                 return 1;
884         if (task_is_stopped_or_traced(p))
885                 return 0;
886         return task_curr(p) || !signal_pending(p);
887 }
888 
889 static void complete_signal(int sig, struct task_struct *p, int group)
890 {
891         struct signal_struct *signal = p->signal;
892         struct task_struct *t;
893 
894         /*
895          * Now find a thread we can wake up to take the signal off the queue.
896          *
897          * If the main thread wants the signal, it gets first crack.
898          * Probably the least surprising to the average bear.
899          */
900         if (wants_signal(sig, p))
901                 t = p;
902         else if (!group || thread_group_empty(p))
903                 /*
904                  * There is just one thread and it does not need to be woken.
905                  * It will dequeue unblocked signals before it runs again.
906                  */
907                 return;
908         else {
909                 /*
910                  * Otherwise try to find a suitable thread.
911                  */
912                 t = signal->curr_target;
913                 while (!wants_signal(sig, t)) {
914                         t = next_thread(t);
915                         if (t == signal->curr_target)
916                                 /*
917                                  * No thread needs to be woken.
918                                  * Any eligible threads will see
919                                  * the signal in the queue soon.
920                                  */
921                                 return;
922                 }
923                 signal->curr_target = t;
924         }
925 
926         /*
927          * Found a killable thread.  If the signal will be fatal,
928          * then start taking the whole group down immediately.
929          */
930         if (sig_fatal(p, sig) &&
931             !(signal->flags & (SIGNAL_UNKILLABLE | SIGNAL_GROUP_EXIT)) &&
932             !sigismember(&t->real_blocked, sig) &&
933             (sig == SIGKILL || !t->ptrace)) {
934                 /*
935                  * This signal will be fatal to the whole group.
936                  */
937                 if (!sig_kernel_coredump(sig)) {
938                         /*
939                          * Start a group exit and wake everybody up.
940                          * This way we don't have other threads
941                          * running and doing things after a slower
942                          * thread has the fatal signal pending.
943                          */
944                         signal->flags = SIGNAL_GROUP_EXIT;
945                         signal->group_exit_code = sig;
946                         signal->group_stop_count = 0;
947                         t = p;
948                         do {
949                                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
950                                 sigaddset(&t->pending.signal, SIGKILL);
951                                 signal_wake_up(t, 1);
952                         } while_each_thread(p, t);
953                         return;
954                 }
955         }
956 
957         /*
958          * The signal is already in the shared-pending queue.
959          * Tell the chosen thread to wake up and dequeue it.
960          */
961         signal_wake_up(t, sig == SIGKILL);
962         return;
963 }
964 
965 static inline int legacy_queue(struct sigpending *signals, int sig)
966 {
967         return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
968 }
969 
970 #ifdef CONFIG_USER_NS
971 static inline void userns_fixup_signal_uid(struct siginfo *info, struct task_struct *t)
972 {
973         if (current_user_ns() == task_cred_xxx(t, user_ns))
974                 return;
975 
976         if (SI_FROMKERNEL(info))
977                 return;
978 
979         rcu_read_lock();
980         info->si_uid = from_kuid_munged(task_cred_xxx(t, user_ns),
981                                         make_kuid(current_user_ns(), info->si_uid));
982         rcu_read_unlock();
983 }
984 #else
985 static inline void userns_fixup_signal_uid(struct siginfo *info, struct task_struct *t)
986 {
987         return;
988 }
989 #endif
990 
991 static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
992                         int group, int from_ancestor_ns)
993 {
994         struct sigpending *pending;
995         struct sigqueue *q;
996         int override_rlimit;
997         int ret = 0, result;
998 
999         assert_spin_locked(&t->sighand->siglock);
1000 
1001         result = TRACE_SIGNAL_IGNORED;
1002         if (!prepare_signal(sig, t,
1003                         from_ancestor_ns || (info == SEND_SIG_FORCED)))
1004                 goto ret;
1005 
1006         pending = group ? &t->signal->shared_pending : &t->pending;
1007         /*
1008          * Short-circuit ignored signals and support queuing
1009          * exactly one non-rt signal, so that we can get more
1010          * detailed information about the cause of the signal.
1011          */
1012         result = TRACE_SIGNAL_ALREADY_PENDING;
1013         if (legacy_queue(pending, sig))
1014                 goto ret;
1015 
1016         result = TRACE_SIGNAL_DELIVERED;
1017         /*
1018          * fast-pathed signals for kernel-internal things like SIGSTOP
1019          * or SIGKILL.
1020          */
1021         if (info == SEND_SIG_FORCED)
1022                 goto out_set;
1023 
1024         /*
1025          * Real-time signals must be queued if sent by sigqueue, or
1026          * some other real-time mechanism.  It is implementation
1027          * defined whether kill() does so.  We attempt to do so, on
1028          * the principle of least surprise, but since kill is not
1029          * allowed to fail with EAGAIN when low on memory we just
1030          * make sure at least one signal gets delivered and don't
1031          * pass on the info struct.
1032          */
1033         if (sig < SIGRTMIN)
1034                 override_rlimit = (is_si_special(info) || info->si_code >= 0);
1035         else
1036                 override_rlimit = 0;
1037 
1038         q = __sigqueue_alloc(sig, t, GFP_ATOMIC | __GFP_NOTRACK_FALSE_POSITIVE,
1039                 override_rlimit);
1040         if (q) {
1041                 list_add_tail(&q->list, &pending->list);
1042                 switch ((unsigned long) info) {
1043                 case (unsigned long) SEND_SIG_NOINFO:
1044                         q->info.si_signo = sig;
1045                         q->info.si_errno = 0;
1046                         q->info.si_code = SI_USER;
1047                         q->info.si_pid = task_tgid_nr_ns(current,
1048                                                         task_active_pid_ns(t));
1049                         q->info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
1050                         break;
1051                 case (unsigned long) SEND_SIG_PRIV:
1052                         q->info.si_signo = sig;
1053                         q->info.si_errno = 0;
1054                         q->info.si_code = SI_KERNEL;
1055                         q->info.si_pid = 0;
1056                         q->info.si_uid = 0;
1057                         break;
1058                 default:
1059                         copy_siginfo(&q->info, info);
1060                         if (from_ancestor_ns)
1061                                 q->info.si_pid = 0;
1062                         break;
1063                 }
1064 
1065                 userns_fixup_signal_uid(&q->info, t);
1066 
1067         } else if (!is_si_special(info)) {
1068                 if (sig >= SIGRTMIN && info->si_code != SI_USER) {
1069                         /*
1070                          * Queue overflow, abort.  We may abort if the
1071                          * signal was rt and sent by user using something
1072                          * other than kill().
1073                          */
1074                         result = TRACE_SIGNAL_OVERFLOW_FAIL;
1075                         ret = -EAGAIN;
1076                         goto ret;
1077                 } else {
1078                         /*
1079                          * This is a silent loss of information.  We still
1080                          * send the signal, but the *info bits are lost.
1081                          */
1082                         result = TRACE_SIGNAL_LOSE_INFO;
1083                 }
1084         }
1085 
1086 out_set:
1087         signalfd_notify(t, sig);
1088         sigaddset(&pending->signal, sig);
1089         complete_signal(sig, t, group);
1090 ret:
1091         trace_signal_generate(sig, info, t, group, result);
1092         return ret;
1093 }
1094 
1095 static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
1096                         int group)
1097 {
1098         int from_ancestor_ns = 0;
1099 
1100 #ifdef CONFIG_PID_NS
1101         from_ancestor_ns = si_fromuser(info) &&
1102                            !task_pid_nr_ns(current, task_active_pid_ns(t));
1103 #endif
1104 
1105         return __send_signal(sig, info, t, group, from_ancestor_ns);
1106 }
1107 
1108 static void print_fatal_signal(int signr)
1109 {
1110         struct pt_regs *regs = signal_pt_regs();
1111         pr_info("potentially unexpected fatal signal %d.\n", signr);
1112 
1113 #if defined(__i386__) && !defined(__arch_um__)
1114         pr_info("code at %08lx: ", regs->ip);
1115         {
1116                 int i;
1117                 for (i = 0; i < 16; i++) {
1118                         unsigned char insn;
1119 
1120                         if (get_user(insn, (unsigned char *)(regs->ip + i)))
1121                                 break;
1122                         pr_cont("%02x ", insn);
1123                 }
1124         }
1125         pr_cont("\n");
1126 #endif
1127         preempt_disable();
1128         show_regs(regs);
1129         preempt_enable();
1130 }
1131 
1132 static int __init setup_print_fatal_signals(char *str)
1133 {
1134         get_option (&str, &print_fatal_signals);
1135 
1136         return 1;
1137 }
1138 
1139 __setup("print-fatal-signals=", setup_print_fatal_signals);
1140 
1141 int
1142 __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
1143 {
1144         return send_signal(sig, info, p, 1);
1145 }
1146 
1147 static int
1148 specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t)
1149 {
1150         return send_signal(sig, info, t, 0);
1151 }
1152 
1153 int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
1154                         bool group)
1155 {
1156         unsigned long flags;
1157         int ret = -ESRCH;
1158 
1159         if (lock_task_sighand(p, &flags)) {
1160                 ret = send_signal(sig, info, p, group);
1161                 unlock_task_sighand(p, &flags);
1162         }
1163 
1164         return ret;
1165 }
1166 
1167 /*
1168  * Force a signal that the process can't ignore: if necessary
1169  * we unblock the signal and change any SIG_IGN to SIG_DFL.
1170  *
1171  * Note: If we unblock the signal, we always reset it to SIG_DFL,
1172  * since we do not want to have a signal handler that was blocked
1173  * be invoked when user space had explicitly blocked it.
1174  *
1175  * We don't want to have recursive SIGSEGV's etc, for example,
1176  * that is why we also clear SIGNAL_UNKILLABLE.
1177  */
1178 int
1179 force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
1180 {
1181         unsigned long int flags;
1182         int ret, blocked, ignored;
1183         struct k_sigaction *action;
1184 
1185         spin_lock_irqsave(&t->sighand->siglock, flags);
1186         action = &t->sighand->action[sig-1];
1187         ignored = action->sa.sa_handler == SIG_IGN;
1188         blocked = sigismember(&t->blocked, sig);
1189         if (blocked || ignored) {
1190                 action->sa.sa_handler = SIG_DFL;
1191                 if (blocked) {
1192                         sigdelset(&t->blocked, sig);
1193                         recalc_sigpending_and_wake(t);
1194                 }
1195         }
1196         if (action->sa.sa_handler == SIG_DFL)
1197                 t->signal->flags &= ~SIGNAL_UNKILLABLE;
1198         ret = specific_send_sig_info(sig, info, t);
1199         spin_unlock_irqrestore(&t->sighand->siglock, flags);
1200 
1201         return ret;
1202 }
1203 
1204 /*
1205  * Nuke all other threads in the group.
1206  */
1207 int zap_other_threads(struct task_struct *p)
1208 {
1209         struct task_struct *t = p;
1210         int count = 0;
1211 
1212         p->signal->group_stop_count = 0;
1213 
1214         while_each_thread(p, t) {
1215                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
1216                 count++;
1217 
1218                 /* Don't bother with already dead threads */
1219                 if (t->exit_state)
1220                         continue;
1221                 sigaddset(&t->pending.signal, SIGKILL);
1222                 signal_wake_up(t, 1);
1223         }
1224 
1225         return count;
1226 }
1227 
1228 struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
1229                                            unsigned long *flags)
1230 {
1231         struct sighand_struct *sighand;
1232 
1233         for (;;) {
1234                 /*
1235                  * Disable interrupts early to avoid deadlocks.
1236                  * See rcu_read_unlock() comment header for details.
1237                  */
1238                 local_irq_save(*flags);
1239                 rcu_read_lock();
1240                 sighand = rcu_dereference(tsk->sighand);
1241                 if (unlikely(sighand == NULL)) {
1242                         rcu_read_unlock();
1243                         local_irq_restore(*flags);
1244                         break;
1245                 }
1246                 /*
1247                  * This sighand can be already freed and even reused, but
1248                  * we rely on SLAB_DESTROY_BY_RCU and sighand_ctor() which
1249                  * initializes ->siglock: this slab can't go away, it has
1250                  * the same object type, ->siglock can't be reinitialized.
1251                  *
1252                  * We need to ensure that tsk->sighand is still the same
1253                  * after we take the lock, we can race with de_thread() or
1254                  * __exit_signal(). In the latter case the next iteration
1255                  * must see ->sighand == NULL.
1256                  */
1257                 spin_lock(&sighand->siglock);
1258                 if (likely(sighand == tsk->sighand)) {
1259                         rcu_read_unlock();
1260                         break;
1261                 }
1262                 spin_unlock(&sighand->siglock);
1263                 rcu_read_unlock();
1264                 local_irq_restore(*flags);
1265         }
1266 
1267         return sighand;
1268 }
1269 
1270 /*
1271  * send signal info to all the members of a group
1272  */
1273 int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
1274 {
1275         int ret;
1276 
1277         rcu_read_lock();
1278         ret = check_kill_permission(sig, info, p);
1279         rcu_read_unlock();
1280 
1281         if (!ret && sig)
1282                 ret = do_send_sig_info(sig, info, p, true);
1283 
1284         return ret;
1285 }
1286 
1287 /*
1288  * __kill_pgrp_info() sends a signal to a process group: this is what the tty
1289  * control characters do (^C, ^Z etc)
1290  * - the caller must hold at least a readlock on tasklist_lock
1291  */
1292 int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp)
1293 {
1294         struct task_struct *p = NULL;
1295         int retval, success;
1296 
1297         success = 0;
1298         retval = -ESRCH;
1299         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
1300                 int err = group_send_sig_info(sig, info, p);
1301                 success |= !err;
1302                 retval = err;
1303         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
1304         return success ? 0 : retval;
1305 }
1306 
1307 int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
1308 {
1309         int error = -ESRCH;
1310         struct task_struct *p;
1311 
1312         for (;;) {
1313                 rcu_read_lock();
1314                 p = pid_task(pid, PIDTYPE_PID);
1315                 if (p)
1316                         error = group_send_sig_info(sig, info, p);
1317                 rcu_read_unlock();
1318                 if (likely(!p || error != -ESRCH))
1319                         return error;
1320 
1321                 /*
1322                  * The task was unhashed in between, try again.  If it
1323                  * is dead, pid_task() will return NULL, if we race with
1324                  * de_thread() it will find the new leader.
1325                  */
1326         }
1327 }
1328 
1329 int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
1330 {
1331         int error;
1332         rcu_read_lock();
1333         error = kill_pid_info(sig, info, find_vpid(pid));
1334         rcu_read_unlock();
1335         return error;
1336 }
1337 
1338 static int kill_as_cred_perm(const struct cred *cred,
1339                              struct task_struct *target)
1340 {
1341         const struct cred *pcred = __task_cred(target);
1342         if (!uid_eq(cred->euid, pcred->suid) && !uid_eq(cred->euid, pcred->uid) &&
1343             !uid_eq(cred->uid,  pcred->suid) && !uid_eq(cred->uid,  pcred->uid))
1344                 return 0;
1345         return 1;
1346 }
1347 
1348 /* like kill_pid_info(), but doesn't use uid/euid of "current" */
1349 int kill_pid_info_as_cred(int sig, struct siginfo *info, struct pid *pid,
1350                          const struct cred *cred, u32 secid)
1351 {
1352         int ret = -EINVAL;
1353         struct task_struct *p;
1354         unsigned long flags;
1355 
1356         if (!valid_signal(sig))
1357                 return ret;
1358 
1359         rcu_read_lock();
1360         p = pid_task(pid, PIDTYPE_PID);
1361         if (!p) {
1362                 ret = -ESRCH;
1363                 goto out_unlock;
1364         }
1365         if (si_fromuser(info) && !kill_as_cred_perm(cred, p)) {
1366                 ret = -EPERM;
1367                 goto out_unlock;
1368         }
1369         ret = security_task_kill(p, info, sig, secid);
1370         if (ret)
1371                 goto out_unlock;
1372 
1373         if (sig) {
1374                 if (lock_task_sighand(p, &flags)) {
1375                         ret = __send_signal(sig, info, p, 1, 0);
1376                         unlock_task_sighand(p, &flags);
1377                 } else
1378                         ret = -ESRCH;
1379         }
1380 out_unlock:
1381         rcu_read_unlock();
1382         return ret;
1383 }
1384 EXPORT_SYMBOL_GPL(kill_pid_info_as_cred);
1385 
1386 /*
1387  * kill_something_info() interprets pid in interesting ways just like kill(2).
1388  *
1389  * POSIX specifies that kill(-1,sig) is unspecified, but what we have
1390  * is probably wrong.  Should make it like BSD or SYSV.
1391  */
1392 
1393 static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
1394 {
1395         int ret;
1396 
1397         if (pid > 0) {
1398                 rcu_read_lock();
1399                 ret = kill_pid_info(sig, info, find_vpid(pid));
1400                 rcu_read_unlock();
1401                 return ret;
1402         }
1403 
1404         read_lock(&tasklist_lock);
1405         if (pid != -1) {
1406                 ret = __kill_pgrp_info(sig, info,
1407                                 pid ? find_vpid(-pid) : task_pgrp(current));
1408         } else {
1409                 int retval = 0, count = 0;
1410                 struct task_struct * p;
1411 
1412                 for_each_process(p) {
1413                         if (task_pid_vnr(p) > 1 &&
1414                                         !same_thread_group(p, current)) {
1415                                 int err = group_send_sig_info(sig, info, p);
1416                                 ++count;
1417                                 if (err != -EPERM)
1418                                         retval = err;
1419                         }
1420                 }
1421                 ret = count ? retval : -ESRCH;
1422         }
1423         read_unlock(&tasklist_lock);
1424 
1425         return ret;
1426 }
1427 
1428 /*
1429  * These are for backward compatibility with the rest of the kernel source.
1430  */
1431 
1432 int send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
1433 {
1434         /*
1435          * Make sure legacy kernel users don't send in bad values
1436          * (normal paths check this in check_kill_permission).
1437          */
1438         if (!valid_signal(sig))
1439                 return -EINVAL;
1440 
1441         return do_send_sig_info(sig, info, p, false);
1442 }
1443 
1444 #define __si_special(priv) \
1445         ((priv) ? SEND_SIG_PRIV : SEND_SIG_NOINFO)
1446 
1447 int
1448 send_sig(int sig, struct task_struct *p, int priv)
1449 {
1450         return send_sig_info(sig, __si_special(priv), p);
1451 }
1452 
1453 void
1454 force_sig(int sig, struct task_struct *p)
1455 {
1456         force_sig_info(sig, SEND_SIG_PRIV, p);
1457 }
1458 
1459 /*
1460  * When things go south during signal handling, we
1461  * will force a SIGSEGV. And if the signal that caused
1462  * the problem was already a SIGSEGV, we'll want to
1463  * make sure we don't even try to deliver the signal..
1464  */
1465 int
1466 force_sigsegv(int sig, struct task_struct *p)
1467 {
1468         if (sig == SIGSEGV) {
1469                 unsigned long flags;
1470                 spin_lock_irqsave(&p->sighand->siglock, flags);
1471                 p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
1472                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
1473         }
1474         force_sig(SIGSEGV, p);
1475         return 0;
1476 }
1477 
1478 int kill_pgrp(struct pid *pid, int sig, int priv)
1479 {
1480         int ret;
1481 
1482         read_lock(&tasklist_lock);
1483         ret = __kill_pgrp_info(sig, __si_special(priv), pid);
1484         read_unlock(&tasklist_lock);
1485 
1486         return ret;
1487 }
1488 EXPORT_SYMBOL(kill_pgrp);
1489 
1490 int kill_pid(struct pid *pid, int sig, int priv)
1491 {
1492         return kill_pid_info(sig, __si_special(priv), pid);
1493 }
1494 EXPORT_SYMBOL(kill_pid);
1495 
1496 /*
1497  * These functions support sending signals using preallocated sigqueue
1498  * structures.  This is needed "because realtime applications cannot
1499  * afford to lose notifications of asynchronous events, like timer
1500  * expirations or I/O completions".  In the case of POSIX Timers
1501  * we allocate the sigqueue structure from the timer_create.  If this
1502  * allocation fails we are able to report the failure to the application
1503  * with an EAGAIN error.
1504  */
1505 struct sigqueue *sigqueue_alloc(void)
1506 {
1507         struct sigqueue *q = __sigqueue_alloc(-1, current, GFP_KERNEL, 0);
1508 
1509         if (q)
1510                 q->flags |= SIGQUEUE_PREALLOC;
1511 
1512         return q;
1513 }
1514 
1515 void sigqueue_free(struct sigqueue *q)
1516 {
1517         unsigned long flags;
1518         spinlock_t *lock = &current->sighand->siglock;
1519 
1520         BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
1521         /*
1522          * We must hold ->siglock while testing q->list
1523          * to serialize with collect_signal() or with
1524          * __exit_signal()->flush_sigqueue().
1525          */
1526         spin_lock_irqsave(lock, flags);
1527         q->flags &= ~SIGQUEUE_PREALLOC;
1528         /*
1529          * If it is queued it will be freed when dequeued,
1530          * like the "regular" sigqueue.
1531          */
1532         if (!list_empty(&q->list))
1533                 q = NULL;
1534         spin_unlock_irqrestore(lock, flags);
1535 
1536         if (q)
1537                 __sigqueue_free(q);
1538 }
1539 
1540 int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
1541 {
1542         int sig = q->info.si_signo;
1543         struct sigpending *pending;
1544         unsigned long flags;
1545         int ret, result;
1546 
1547         BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
1548 
1549         ret = -1;
1550         if (!likely(lock_task_sighand(t, &flags)))
1551                 goto ret;
1552 
1553         ret = 1; /* the signal is ignored */
1554         result = TRACE_SIGNAL_IGNORED;
1555         if (!prepare_signal(sig, t, false))
1556                 goto out;
1557 
1558         ret = 0;
1559         if (unlikely(!list_empty(&q->list))) {
1560                 /*
1561                  * If an SI_TIMER entry is already queue just increment
1562                  * the overrun count.
1563                  */
1564                 BUG_ON(q->info.si_code != SI_TIMER);
1565                 q->info.si_overrun++;
1566                 result = TRACE_SIGNAL_ALREADY_PENDING;
1567                 goto out;
1568         }
1569         q->info.si_overrun = 0;
1570 
1571         signalfd_notify(t, sig);
1572         pending = group ? &t->signal->shared_pending : &t->pending;
1573         list_add_tail(&q->list, &pending->list);
1574         sigaddset(&pending->signal, sig);
1575         complete_signal(sig, t, group);
1576         result = TRACE_SIGNAL_DELIVERED;
1577 out:
1578         trace_signal_generate(sig, &q->info, t, group, result);
1579         unlock_task_sighand(t, &flags);
1580 ret:
1581         return ret;
1582 }
1583 
1584 /*
1585  * Let a parent know about the death of a child.
1586  * For a stopped/continued status change, use do_notify_parent_cldstop instead.
1587  *
1588  * Returns true if our parent ignored us and so we've switched to
1589  * self-reaping.
1590  */
1591 bool do_notify_parent(struct task_struct *tsk, int sig)
1592 {
1593         struct siginfo info;
1594         unsigned long flags;
1595         struct sighand_struct *psig;
1596         bool autoreap = false;
1597         u64 utime, stime;
1598 
1599         BUG_ON(sig == -1);
1600 
1601         /* do_notify_parent_cldstop should have been called instead.  */
1602         BUG_ON(task_is_stopped_or_traced(tsk));
1603 
1604         BUG_ON(!tsk->ptrace &&
1605                (tsk->group_leader != tsk || !thread_group_empty(tsk)));
1606 
1607         if (sig != SIGCHLD) {
1608                 /*
1609                  * This is only possible if parent == real_parent.
1610                  * Check if it has changed security domain.
1611                  */
1612                 if (tsk->parent_exec_id != tsk->parent->self_exec_id)
1613                         sig = SIGCHLD;
1614         }
1615 
1616         info.si_signo = sig;
1617         info.si_errno = 0;
1618         /*
1619          * We are under tasklist_lock here so our parent is tied to
1620          * us and cannot change.
1621          *
1622          * task_active_pid_ns will always return the same pid namespace
1623          * until a task passes through release_task.
1624          *
1625          * write_lock() currently calls preempt_disable() which is the
1626          * same as rcu_read_lock(), but according to Oleg, this is not
1627          * correct to rely on this
1628          */
1629         rcu_read_lock();
1630         info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(tsk->parent));
1631         info.si_uid = from_kuid_munged(task_cred_xxx(tsk->parent, user_ns),
1632                                        task_uid(tsk));
1633         rcu_read_unlock();
1634 
1635         task_cputime(tsk, &utime, &stime);
1636         info.si_utime = nsec_to_clock_t(utime + tsk->signal->utime);
1637         info.si_stime = nsec_to_clock_t(stime + tsk->signal->stime);
1638 
1639         info.si_status = tsk->exit_code & 0x7f;
1640         if (tsk->exit_code & 0x80)
1641                 info.si_code = CLD_DUMPED;
1642         else if (tsk->exit_code & 0x7f)
1643                 info.si_code = CLD_KILLED;
1644         else {
1645                 info.si_code = CLD_EXITED;
1646                 info.si_status = tsk->exit_code >> 8;
1647         }
1648 
1649         psig = tsk->parent->sighand;
1650         spin_lock_irqsave(&psig->siglock, flags);
1651         if (!tsk->ptrace && sig == SIGCHLD &&
1652             (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
1653              (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) {
1654                 /*
1655                  * We are exiting and our parent doesn't care.  POSIX.1
1656                  * defines special semantics for setting SIGCHLD to SIG_IGN
1657                  * or setting the SA_NOCLDWAIT flag: we should be reaped
1658                  * automatically and not left for our parent's wait4 call.
1659                  * Rather than having the parent do it as a magic kind of
1660                  * signal handler, we just set this to tell do_exit that we
1661                  * can be cleaned up without becoming a zombie.  Note that
1662                  * we still call __wake_up_parent in this case, because a
1663                  * blocked sys_wait4 might now return -ECHILD.
1664                  *
1665                  * Whether we send SIGCHLD or not for SA_NOCLDWAIT
1666                  * is implementation-defined: we do (if you don't want
1667                  * it, just use SIG_IGN instead).
1668                  */
1669                 autoreap = true;
1670                 if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
1671                         sig = 0;
1672         }
1673         if (valid_signal(sig) && sig)
1674                 __group_send_sig_info(sig, &info, tsk->parent);
1675         __wake_up_parent(tsk, tsk->parent);
1676         spin_unlock_irqrestore(&psig->siglock, flags);
1677 
1678         return autoreap;
1679 }
1680 
1681 /**
1682  * do_notify_parent_cldstop - notify parent of stopped/continued state change
1683  * @tsk: task reporting the state change
1684  * @for_ptracer: the notification is for ptracer
1685  * @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report
1686  *
1687  * Notify @tsk's parent that the stopped/continued state has changed.  If
1688  * @for_ptracer is %false, @tsk's group leader notifies to its real parent.
1689  * If %true, @tsk reports to @tsk->parent which should be the ptracer.
1690  *
1691  * CONTEXT:
1692  * Must be called with tasklist_lock at least read locked.
1693  */
1694 static void do_notify_parent_cldstop(struct task_struct *tsk,
1695                                      bool for_ptracer, int why)
1696 {
1697         struct siginfo info;
1698         unsigned long flags;
1699         struct task_struct *parent;
1700         struct sighand_struct *sighand;
1701         u64 utime, stime;
1702 
1703         if (for_ptracer) {
1704                 parent = tsk->parent;
1705         } else {
1706                 tsk = tsk->group_leader;
1707                 parent = tsk->real_parent;
1708         }
1709 
1710         info.si_signo = SIGCHLD;
1711         info.si_errno = 0;
1712         /*
1713          * see comment in do_notify_parent() about the following 4 lines
1714          */
1715         rcu_read_lock();
1716         info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(parent));
1717         info.si_uid = from_kuid_munged(task_cred_xxx(parent, user_ns), task_uid(tsk));
1718         rcu_read_unlock();
1719 
1720         task_cputime(tsk, &utime, &stime);
1721         info.si_utime = nsec_to_clock_t(utime);
1722         info.si_stime = nsec_to_clock_t(stime);
1723 
1724         info.si_code = why;
1725         switch (why) {
1726         case CLD_CONTINUED:
1727                 info.si_status = SIGCONT;
1728                 break;
1729         case CLD_STOPPED:
1730                 info.si_status = tsk->signal->group_exit_code & 0x7f;
1731                 break;
1732         case CLD_TRAPPED:
1733                 info.si_status = tsk->exit_code & 0x7f;
1734                 break;
1735         default:
1736                 BUG();
1737         }
1738 
1739         sighand = parent->sighand;
1740         spin_lock_irqsave(&sighand->siglock, flags);
1741         if (sighand->action[SIGCHLD-1].sa.sa_handler != SIG_IGN &&
1742             !(sighand->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
1743                 __group_send_sig_info(SIGCHLD, &info, parent);
1744         /*
1745          * Even if SIGCHLD is not generated, we must wake up wait4 calls.
1746          */
1747         __wake_up_parent(tsk, parent);
1748         spin_unlock_irqrestore(&sighand->siglock, flags);
1749 }
1750 
1751 static inline int may_ptrace_stop(void)
1752 {
1753         if (!likely(current->ptrace))
1754                 return 0;
1755         /*
1756          * Are we in the middle of do_coredump?
1757          * If so and our tracer is also part of the coredump stopping
1758          * is a deadlock situation, and pointless because our tracer
1759          * is dead so don't allow us to stop.
1760          * If SIGKILL was already sent before the caller unlocked
1761          * ->siglock we must see ->core_state != NULL. Otherwise it
1762          * is safe to enter schedule().
1763          *
1764          * This is almost outdated, a task with the pending SIGKILL can't
1765          * block in TASK_TRACED. But PTRACE_EVENT_EXIT can be reported
1766          * after SIGKILL was already dequeued.
1767          */
1768         if (unlikely(current->mm->core_state) &&
1769             unlikely(current->mm == current->parent->mm))
1770                 return 0;
1771 
1772         return 1;
1773 }
1774 
1775 /*
1776  * Return non-zero if there is a SIGKILL that should be waking us up.
1777  * Called with the siglock held.
1778  */
1779 static int sigkill_pending(struct task_struct *tsk)
1780 {
1781         return  sigismember(&tsk->pending.signal, SIGKILL) ||
1782                 sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
1783 }
1784 
1785 /*
1786  * This must be called with current->sighand->siglock held.
1787  *
1788  * This should be the path for all ptrace stops.
1789  * We always set current->last_siginfo while stopped here.
1790  * That makes it a way to test a stopped process for
1791  * being ptrace-stopped vs being job-control-stopped.
1792  *
1793  * If we actually decide not to stop at all because the tracer
1794  * is gone, we keep current->exit_code unless clear_code.
1795  */
1796 static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
1797         __releases(&current->sighand->siglock)
1798         __acquires(&current->sighand->siglock)
1799 {
1800         bool gstop_done = false;
1801 
1802         if (arch_ptrace_stop_needed(exit_code, info)) {
1803                 /*
1804                  * The arch code has something special to do before a
1805                  * ptrace stop.  This is allowed to block, e.g. for faults
1806                  * on user stack pages.  We can't keep the siglock while
1807                  * calling arch_ptrace_stop, so we must release it now.
1808                  * To preserve proper semantics, we must do this before
1809                  * any signal bookkeeping like checking group_stop_count.
1810                  * Meanwhile, a SIGKILL could come in before we retake the
1811                  * siglock.  That must prevent us from sleeping in TASK_TRACED.
1812                  * So after regaining the lock, we must check for SIGKILL.
1813                  */
1814                 spin_unlock_irq(&current->sighand->siglock);
1815                 arch_ptrace_stop(exit_code, info);
1816                 spin_lock_irq(&current->sighand->siglock);
1817                 if (sigkill_pending(current))
1818                         return;
1819         }
1820 
1821         /*
1822          * We're committing to trapping.  TRACED should be visible before
1823          * TRAPPING is cleared; otherwise, the tracer might fail do_wait().
1824          * Also, transition to TRACED and updates to ->jobctl should be
1825          * atomic with respect to siglock and should be done after the arch
1826          * hook as siglock is released and regrabbed across it.
1827          */
1828         set_current_state(TASK_TRACED);
1829 
1830         current->last_siginfo = info;
1831         current->exit_code = exit_code;
1832 
1833         /*
1834          * If @why is CLD_STOPPED, we're trapping to participate in a group
1835          * stop.  Do the bookkeeping.  Note that if SIGCONT was delievered
1836          * across siglock relocks since INTERRUPT was scheduled, PENDING
1837          * could be clear now.  We act as if SIGCONT is received after
1838          * TASK_TRACED is entered - ignore it.
1839          */
1840         if (why == CLD_STOPPED && (current->jobctl & JOBCTL_STOP_PENDING))
1841                 gstop_done = task_participate_group_stop(current);
1842 
1843         /* any trap clears pending STOP trap, STOP trap clears NOTIFY */
1844         task_clear_jobctl_pending(current, JOBCTL_TRAP_STOP);
1845         if (info && info->si_code >> 8 == PTRACE_EVENT_STOP)
1846                 task_clear_jobctl_pending(current, JOBCTL_TRAP_NOTIFY);
1847 
1848         /* entering a trap, clear TRAPPING */
1849         task_clear_jobctl_trapping(current);
1850 
1851         spin_unlock_irq(&current->sighand->siglock);
1852         read_lock(&tasklist_lock);
1853         if (may_ptrace_stop()) {
1854                 /*
1855                  * Notify parents of the stop.
1856                  *
1857                  * While ptraced, there are two parents - the ptracer and
1858                  * the real_parent of the group_leader.  The ptracer should
1859                  * know about every stop while the real parent is only
1860                  * interested in the completion of group stop.  The states
1861                  * for the two don't interact with each other.  Notify
1862                  * separately unless they're gonna be duplicates.
1863                  */
1864                 do_notify_parent_cldstop(current, true, why);
1865                 if (gstop_done && ptrace_reparented(current))
1866                         do_notify_parent_cldstop(current, false, why);
1867 
1868                 /*
1869                  * Don't want to allow preemption here, because
1870                  * sys_ptrace() needs this task to be inactive.
1871                  *
1872                  * XXX: implement read_unlock_no_resched().
1873                  */
1874                 preempt_disable();
1875                 read_unlock(&tasklist_lock);
1876                 preempt_enable_no_resched();
1877                 freezable_schedule();
1878         } else {
1879                 /*
1880                  * By the time we got the lock, our tracer went away.
1881                  * Don't drop the lock yet, another tracer may come.
1882                  *
1883                  * If @gstop_done, the ptracer went away between group stop
1884                  * completion and here.  During detach, it would have set
1885                  * JOBCTL_STOP_PENDING on us and we'll re-enter
1886                  * TASK_STOPPED in do_signal_stop() on return, so notifying
1887                  * the real parent of the group stop completion is enough.
1888                  */
1889                 if (gstop_done)
1890                         do_notify_parent_cldstop(current, false, why);
1891 
1892                 /* tasklist protects us from ptrace_freeze_traced() */
1893                 __set_current_state(TASK_RUNNING);
1894                 if (clear_code)
1895                         current->exit_code = 0;
1896                 read_unlock(&tasklist_lock);
1897         }
1898 
1899         /*
1900          * We are back.  Now reacquire the siglock before touching
1901          * last_siginfo, so that we are sure to have synchronized with
1902          * any signal-sending on another CPU that wants to examine it.
1903          */
1904         spin_lock_irq(&current->sighand->siglock);
1905         current->last_siginfo = NULL;
1906 
1907         /* LISTENING can be set only during STOP traps, clear it */
1908         current->jobctl &= ~JOBCTL_LISTENING;
1909 
1910         /*
1911          * Queued signals ignored us while we were stopped for tracing.
1912          * So check for any that we should take before resuming user mode.
1913          * This sets TIF_SIGPENDING, but never clears it.
1914          */
1915         recalc_sigpending_tsk(current);
1916 }
1917 
1918 static void ptrace_do_notify(int signr, int exit_code, int why)
1919 {
1920         siginfo_t info;
1921 
1922         memset(&info, 0, sizeof info);
1923         info.si_signo = signr;
1924         info.si_code = exit_code;
1925         info.si_pid = task_pid_vnr(current);
1926         info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
1927 
1928         /* Let the debugger run.  */
1929         ptrace_stop(exit_code, why, 1, &info);
1930 }
1931 
1932 void ptrace_notify(int exit_code)
1933 {
1934         BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
1935         if (unlikely(current->task_works))
1936                 task_work_run();
1937 
1938         spin_lock_irq(&current->sighand->siglock);
1939         ptrace_do_notify(SIGTRAP, exit_code, CLD_TRAPPED);
1940         spin_unlock_irq(&current->sighand->siglock);
1941 }
1942 
1943 /**
1944  * do_signal_stop - handle group stop for SIGSTOP and other stop signals
1945  * @signr: signr causing group stop if initiating
1946  *
1947  * If %JOBCTL_STOP_PENDING is not set yet, initiate group stop with @signr
1948  * and participate in it.  If already set, participate in the existing
1949  * group stop.  If participated in a group stop (and thus slept), %true is
1950  * returned with siglock released.
1951  *
1952  * If ptraced, this function doesn't handle stop itself.  Instead,
1953  * %JOBCTL_TRAP_STOP is scheduled and %false is returned with siglock
1954  * untouched.  The caller must ensure that INTERRUPT trap handling takes
1955  * places afterwards.
1956  *
1957  * CONTEXT:
1958  * Must be called with @current->sighand->siglock held, which is released
1959  * on %true return.
1960  *
1961  * RETURNS:
1962  * %false if group stop is already cancelled or ptrace trap is scheduled.
1963  * %true if participated in group stop.
1964  */
1965 static bool do_signal_stop(int signr)
1966         __releases(&current->sighand->siglock)
1967 {
1968         struct signal_struct *sig = current->signal;
1969 
1970         if (!(current->jobctl & JOBCTL_STOP_PENDING)) {
1971                 unsigned long gstop = JOBCTL_STOP_PENDING | JOBCTL_STOP_CONSUME;
1972                 struct task_struct *t;
1973 
1974                 /* signr will be recorded in task->jobctl for retries */
1975                 WARN_ON_ONCE(signr & ~JOBCTL_STOP_SIGMASK);
1976 
1977                 if (!likely(current->jobctl & JOBCTL_STOP_DEQUEUED) ||
1978                     unlikely(signal_group_exit(sig)))
1979                         return false;
1980                 /*
1981                  * There is no group stop already in progress.  We must
1982                  * initiate one now.
1983                  *
1984                  * While ptraced, a task may be resumed while group stop is
1985                  * still in effect and then receive a stop signal and
1986                  * initiate another group stop.  This deviates from the
1987                  * usual behavior as two consecutive stop signals can't
1988                  * cause two group stops when !ptraced.  That is why we
1989                  * also check !task_is_stopped(t) below.
1990                  *
1991                  * The condition can be distinguished by testing whether
1992                  * SIGNAL_STOP_STOPPED is already set.  Don't generate
1993                  * group_exit_code in such case.
1994                  *
1995                  * This is not necessary for SIGNAL_STOP_CONTINUED because
1996                  * an intervening stop signal is required to cause two
1997                  * continued events regardless of ptrace.
1998                  */
1999                 if (!(sig->flags & SIGNAL_STOP_STOPPED))
2000                         sig->group_exit_code = signr;
2001 
2002                 sig->group_stop_count = 0;
2003 
2004                 if (task_set_jobctl_pending(current, signr | gstop))
2005                         sig->group_stop_count++;
2006 
2007                 t = current;
2008                 while_each_thread(current, t) {
2009                         /*
2010                          * Setting state to TASK_STOPPED for a group
2011                          * stop is always done with the siglock held,
2012                          * so this check has no races.
2013                          */
2014                         if (!task_is_stopped(t) &&
2015                             task_set_jobctl_pending(t, signr | gstop)) {
2016                                 sig->group_stop_count++;
2017                                 if (likely(!(t->ptrace & PT_SEIZED)))
2018                                         signal_wake_up(t, 0);
2019                                 else
2020                                         ptrace_trap_notify(t);
2021                         }
2022                 }
2023         }
2024 
2025         if (likely(!current->ptrace)) {
2026                 int notify = 0;
2027 
2028                 /*
2029                  * If there are no other threads in the group, or if there
2030                  * is a group stop in progress and we are the last to stop,
2031                  * report to the parent.
2032                  */
2033                 if (task_participate_group_stop(current))
2034                         notify = CLD_STOPPED;
2035 
2036                 __set_current_state(TASK_STOPPED);
2037                 spin_unlock_irq(&current->sighand->siglock);
2038 
2039                 /*
2040                  * Notify the parent of the group stop completion.  Because
2041                  * we're not holding either the siglock or tasklist_lock
2042                  * here, ptracer may attach inbetween; however, this is for
2043                  * group stop and should always be delivered to the real
2044                  * parent of the group leader.  The new ptracer will get
2045                  * its notification when this task transitions into
2046                  * TASK_TRACED.
2047                  */
2048                 if (notify) {
2049                         read_lock(&tasklist_lock);
2050                         do_notify_parent_cldstop(current, false, notify);
2051                         read_unlock(&tasklist_lock);
2052                 }
2053 
2054                 /* Now we don't run again until woken by SIGCONT or SIGKILL */
2055                 freezable_schedule();
2056                 return true;
2057         } else {
2058                 /*
2059                  * While ptraced, group stop is handled by STOP trap.
2060                  * Schedule it and let the caller deal with it.
2061                  */
2062                 task_set_jobctl_pending(current, JOBCTL_TRAP_STOP);
2063                 return false;
2064         }
2065 }
2066 
2067 /**
2068  * do_jobctl_trap - take care of ptrace jobctl traps
2069  *
2070  * When PT_SEIZED, it's used for both group stop and explicit
2071  * SEIZE/INTERRUPT traps.  Both generate PTRACE_EVENT_STOP trap with
2072  * accompanying siginfo.  If stopped, lower eight bits of exit_code contain
2073  * the stop signal; otherwise, %SIGTRAP.
2074  *
2075  * When !PT_SEIZED, it's used only for group stop trap with stop signal
2076  * number as exit_code and no siginfo.
2077  *
2078  * CONTEXT:
2079  * Must be called with @current->sighand->siglock held, which may be
2080  * released and re-acquired before returning with intervening sleep.
2081  */
2082 static void do_jobctl_trap(void)
2083 {
2084         struct signal_struct *signal = current->signal;
2085         int signr = current->jobctl & JOBCTL_STOP_SIGMASK;
2086 
2087         if (current->ptrace & PT_SEIZED) {
2088                 if (!signal->group_stop_count &&
2089                     !(signal->flags & SIGNAL_STOP_STOPPED))
2090                         signr = SIGTRAP;
2091                 WARN_ON_ONCE(!signr);
2092                 ptrace_do_notify(signr, signr | (PTRACE_EVENT_STOP << 8),
2093                                  CLD_STOPPED);
2094         } else {
2095                 WARN_ON_ONCE(!signr);
2096                 ptrace_stop(signr, CLD_STOPPED, 0, NULL);
2097                 current->exit_code = 0;
2098         }
2099 }
2100 
2101 static int ptrace_signal(int signr, siginfo_t *info)
2102 {
2103         ptrace_signal_deliver();
2104         /*
2105          * We do not check sig_kernel_stop(signr) but set this marker
2106          * unconditionally because we do not know whether debugger will
2107          * change signr. This flag has no meaning unless we are going
2108          * to stop after return from ptrace_stop(). In this case it will
2109          * be checked in do_signal_stop(), we should only stop if it was
2110          * not cleared by SIGCONT while we were sleeping. See also the
2111          * comment in dequeue_signal().
2112          */
2113         current->jobctl |= JOBCTL_STOP_DEQUEUED;
2114         ptrace_stop(signr, CLD_TRAPPED, 0, info);
2115 
2116         /* We're back.  Did the debugger cancel the sig?  */
2117         signr = current->exit_code;
2118         if (signr == 0)
2119                 return signr;
2120 
2121         current->exit_code = 0;
2122 
2123         /*
2124          * Update the siginfo structure if the signal has
2125          * changed.  If the debugger wanted something
2126          * specific in the siginfo structure then it should
2127          * have updated *info via PTRACE_SETSIGINFO.
2128          */
2129         if (signr != info->si_signo) {
2130                 info->si_signo = signr;
2131                 info->si_errno = 0;
2132                 info->si_code = SI_USER;
2133                 rcu_read_lock();
2134                 info->si_pid = task_pid_vnr(current->parent);
2135                 info->si_uid = from_kuid_munged(current_user_ns(),
2136                                                 task_uid(current->parent));
2137                 rcu_read_unlock();
2138         }
2139 
2140         /* If the (new) signal is now blocked, requeue it.  */
2141         if (sigismember(&current->blocked, signr)) {
2142                 specific_send_sig_info(signr, info, current);
2143                 signr = 0;
2144         }
2145 
2146         return signr;
2147 }
2148 
2149 int get_signal(struct ksignal *ksig)
2150 {
2151         struct sighand_struct *sighand = current->sighand;
2152         struct signal_struct *signal = current->signal;
2153         int signr;
2154 
2155         if (unlikely(current->task_works))
2156                 task_work_run();
2157 
2158         if (unlikely(uprobe_deny_signal()))
2159                 return 0;
2160 
2161         /*
2162          * Do this once, we can't return to user-mode if freezing() == T.
2163          * do_signal_stop() and ptrace_stop() do freezable_schedule() and
2164          * thus do not need another check after return.
2165          */
2166         try_to_freeze();
2167 
2168 relock:
2169         spin_lock_irq(&sighand->siglock);
2170         /*
2171          * Every stopped thread goes here after wakeup. Check to see if
2172          * we should notify the parent, prepare_signal(SIGCONT) encodes
2173          * the CLD_ si_code into SIGNAL_CLD_MASK bits.
2174          */
2175         if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
2176                 int why;
2177 
2178                 if (signal->flags & SIGNAL_CLD_CONTINUED)
2179                         why = CLD_CONTINUED;
2180                 else
2181                         why = CLD_STOPPED;
2182 
2183                 signal->flags &= ~SIGNAL_CLD_MASK;
2184 
2185                 spin_unlock_irq(&sighand->siglock);
2186 
2187                 /*
2188                  * Notify the parent that we're continuing.  This event is
2189                  * always per-process and doesn't make whole lot of sense
2190                  * for ptracers, who shouldn't consume the state via
2191                  * wait(2) either, but, for backward compatibility, notify
2192                  * the ptracer of the group leader too unless it's gonna be
2193                  * a duplicate.
2194                  */
2195                 read_lock(&tasklist_lock);
2196                 do_notify_parent_cldstop(current, false, why);
2197 
2198                 if (ptrace_reparented(current->group_leader))
2199                         do_notify_parent_cldstop(current->group_leader,
2200                                                 true, why);
2201                 read_unlock(&tasklist_lock);
2202 
2203                 goto relock;
2204         }
2205 
2206         for (;;) {
2207                 struct k_sigaction *ka;
2208 
2209                 if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) &&
2210                     do_signal_stop(0))
2211                         goto relock;
2212 
2213                 if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) {
2214                         do_jobctl_trap();
2215                         spin_unlock_irq(&sighand->siglock);
2216                         goto relock;
2217                 }
2218 
2219                 signr = dequeue_signal(current, &current->blocked, &ksig->info);
2220 
2221                 if (!signr)
2222                         break; /* will return 0 */
2223 
2224                 if (unlikely(current->ptrace) && signr != SIGKILL) {
2225                         signr = ptrace_signal(signr, &ksig->info);
2226                         if (!signr)
2227                                 continue;
2228                 }
2229 
2230                 ka = &sighand->action[signr-1];
2231 
2232                 /* Trace actually delivered signals. */
2233                 trace_signal_deliver(signr, &ksig->info, ka);
2234 
2235                 if (ka->sa.sa_handler == SIG_IGN) /* Do nothing.  */
2236                         continue;
2237                 if (ka->sa.sa_handler != SIG_DFL) {
2238                         /* Run the handler.  */
2239                         ksig->ka = *ka;
2240 
2241                         if (ka->sa.sa_flags & SA_ONESHOT)
2242                                 ka->sa.sa_handler = SIG_DFL;
2243 
2244                         break; /* will return non-zero "signr" value */
2245                 }
2246 
2247                 /*
2248                  * Now we are doing the default action for this signal.
2249                  */
2250                 if (sig_kernel_ignore(signr)) /* Default is nothing. */
2251                         continue;
2252 
2253                 /*
2254                  * Global init gets no signals it doesn't want.
2255                  * Container-init gets no signals it doesn't want from same
2256                  * container.
2257                  *
2258                  * Note that if global/container-init sees a sig_kernel_only()
2259                  * signal here, the signal must have been generated internally
2260                  * or must have come from an ancestor namespace. In either
2261                  * case, the signal cannot be dropped.
2262                  */
2263                 if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
2264                                 !sig_kernel_only(signr))
2265                         continue;
2266 
2267                 if (sig_kernel_stop(signr)) {
2268                         /*
2269                          * The default action is to stop all threads in
2270                          * the thread group.  The job control signals
2271                          * do nothing in an orphaned pgrp, but SIGSTOP
2272                          * always works.  Note that siglock needs to be
2273                          * dropped during the call to is_orphaned_pgrp()
2274                          * because of lock ordering with tasklist_lock.
2275                          * This allows an intervening SIGCONT to be posted.
2276                          * We need to check for that and bail out if necessary.
2277                          */
2278                         if (signr != SIGSTOP) {
2279                                 spin_unlock_irq(&sighand->siglock);
2280 
2281                                 /* signals can be posted during this window */
2282 
2283                                 if (is_current_pgrp_orphaned())
2284                                         goto relock;
2285 
2286                                 spin_lock_irq(&sighand->siglock);
2287                         }
2288 
2289                         if (likely(do_signal_stop(ksig->info.si_signo))) {
2290                                 /* It released the siglock.  */
2291                                 goto relock;
2292                         }
2293 
2294                         /*
2295                          * We didn't actually stop, due to a race
2296                          * with SIGCONT or something like that.
2297                          */
2298                         continue;
2299                 }
2300 
2301                 spin_unlock_irq(&sighand->siglock);
2302 
2303                 /*
2304                  * Anything else is fatal, maybe with a core dump.
2305                  */
2306                 current->flags |= PF_SIGNALED;
2307 
2308                 if (sig_kernel_coredump(signr)) {
2309                         if (print_fatal_signals)
2310                                 print_fatal_signal(ksig->info.si_signo);
2311                         proc_coredump_connector(current);
2312                         /*
2313                          * If it was able to dump core, this kills all
2314                          * other threads in the group and synchronizes with
2315                          * their demise.  If we lost the race with another
2316                          * thread getting here, it set group_exit_code
2317                          * first and our do_group_exit call below will use
2318                          * that value and ignore the one we pass it.
2319                          */
2320                         do_coredump(&ksig->info);
2321                 }
2322 
2323                 /*
2324                  * Death signals, no core dump.
2325                  */
2326                 do_group_exit(ksig->info.si_signo);
2327                 /* NOTREACHED */
2328         }
2329         spin_unlock_irq(&sighand->siglock);
2330 
2331         ksig->sig = signr;
2332         return ksig->sig > 0;
2333 }
2334 
2335 /**
2336  * signal_delivered - 
2337  * @ksig:               kernel signal struct
2338  * @stepping:           nonzero if debugger single-step or block-step in use
2339  *
2340  * This function should be called when a signal has successfully been
2341  * delivered. It updates the blocked signals accordingly (@ksig->ka.sa.sa_mask
2342  * is always blocked, and the signal itself is blocked unless %SA_NODEFER
2343  * is set in @ksig->ka.sa.sa_flags.  Tracing is notified.
2344  */
2345 static void signal_delivered(struct ksignal *ksig, int stepping)
2346 {
2347         sigset_t blocked;
2348 
2349         /* A signal was successfully delivered, and the
2350            saved sigmask was stored on the signal frame,
2351            and will be restored by sigreturn.  So we can
2352            simply clear the restore sigmask flag.  */
2353         clear_restore_sigmask();
2354 
2355         sigorsets(&blocked, &current->blocked, &ksig->ka.sa.sa_mask);
2356         if (!(ksig->ka.sa.sa_flags & SA_NODEFER))
2357                 sigaddset(&blocked, ksig->sig);
2358         set_current_blocked(&blocked);
2359         tracehook_signal_handler(stepping);
2360 }
2361 
2362 void signal_setup_done(int failed, struct ksignal *ksig, int stepping)
2363 {
2364         if (failed)
2365                 force_sigsegv(ksig->sig, current);
2366         else
2367                 signal_delivered(ksig, stepping);
2368 }
2369 
2370 /*
2371  * It could be that complete_signal() picked us to notify about the
2372  * group-wide signal. Other threads should be notified now to take
2373  * the shared signals in @which since we will not.
2374  */
2375 static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)
2376 {
2377         sigset_t retarget;
2378         struct task_struct *t;
2379 
2380         sigandsets(&retarget, &tsk->signal->shared_pending.signal, which);
2381         if (sigisemptyset(&retarget))
2382                 return;
2383 
2384         t = tsk;
2385         while_each_thread(tsk, t) {
2386                 if (t->flags & PF_EXITING)
2387                         continue;
2388 
2389                 if (!has_pending_signals(&retarget, &t->blocked))
2390                         continue;
2391                 /* Remove the signals this thread can handle. */
2392                 sigandsets(&retarget, &retarget, &t->blocked);
2393 
2394                 if (!signal_pending(t))
2395                         signal_wake_up(t, 0);
2396 
2397                 if (sigisemptyset(&retarget))
2398                         break;
2399         }
2400 }
2401 
2402 void exit_signals(struct task_struct *tsk)
2403 {
2404         int group_stop = 0;
2405         sigset_t unblocked;
2406 
2407         /*
2408          * @tsk is about to have PF_EXITING set - lock out users which
2409          * expect stable threadgroup.
2410          */
2411         cgroup_threadgroup_change_begin(tsk);
2412 
2413         if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
2414                 tsk->flags |= PF_EXITING;
2415                 cgroup_threadgroup_change_end(tsk);
2416                 return;
2417         }
2418 
2419         spin_lock_irq(&tsk->sighand->siglock);
2420         /*
2421          * From now this task is not visible for group-wide signals,
2422          * see wants_signal(), do_signal_stop().
2423          */
2424         tsk->flags |= PF_EXITING;
2425 
2426         cgroup_threadgroup_change_end(tsk);
2427 
2428         if (!signal_pending(tsk))
2429                 goto out;
2430 
2431         unblocked = tsk->blocked;
2432         signotset(&unblocked);
2433         retarget_shared_pending(tsk, &unblocked);
2434 
2435         if (unlikely(tsk->jobctl & JOBCTL_STOP_PENDING) &&
2436             task_participate_group_stop(tsk))
2437                 group_stop = CLD_STOPPED;
2438 out:
2439         spin_unlock_irq(&tsk->sighand->siglock);
2440 
2441         /*
2442          * If group stop has completed, deliver the notification.  This
2443          * should always go to the real parent of the group leader.
2444          */
2445         if (unlikely(group_stop)) {
2446                 read_lock(&tasklist_lock);
2447                 do_notify_parent_cldstop(tsk, false, group_stop);
2448                 read_unlock(&tasklist_lock);
2449         }
2450 }
2451 
2452 EXPORT_SYMBOL(recalc_sigpending);
2453 EXPORT_SYMBOL_GPL(dequeue_signal);
2454 EXPORT_SYMBOL(flush_signals);
2455 EXPORT_SYMBOL(force_sig);
2456 EXPORT_SYMBOL(send_sig);
2457 EXPORT_SYMBOL(send_sig_info);
2458 EXPORT_SYMBOL(sigprocmask);
2459 
2460 /*
2461  * System call entry points.
2462  */
2463 
2464 /**
2465  *  sys_restart_syscall - restart a system call
2466  */
2467 SYSCALL_DEFINE0(restart_syscall)
2468 {
2469         struct restart_block *restart = &current->restart_block;
2470         return restart->fn(restart);
2471 }
2472 
2473 long do_no_restart_syscall(struct restart_block *param)
2474 {
2475         return -EINTR;
2476 }
2477 
2478 static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
2479 {
2480         if (signal_pending(tsk) && !thread_group_empty(tsk)) {
2481                 sigset_t newblocked;
2482                 /* A set of now blocked but previously unblocked signals. */
2483                 sigandnsets(&newblocked, newset, &current->blocked);
2484                 retarget_shared_pending(tsk, &newblocked);
2485         }
2486         tsk->blocked = *newset;
2487         recalc_sigpending();
2488 }
2489 
2490 /**
2491  * set_current_blocked - change current->blocked mask
2492  * @newset: new mask
2493  *
2494  * It is wrong to change ->blocked directly, this helper should be used
2495  * to ensure the process can't miss a shared signal we are going to block.
2496  */
2497 void set_current_blocked(sigset_t *newset)
2498 {
2499         sigdelsetmask(newset, sigmask(SIGKILL) | sigmask(SIGSTOP));
2500         __set_current_blocked(newset);
2501 }
2502 
2503 void __set_current_blocked(const sigset_t *newset)
2504 {
2505         struct task_struct *tsk = current;
2506 
2507         /*
2508          * In case the signal mask hasn't changed, there is nothing we need
2509          * to do. The current->blocked shouldn't be modified by other task.
2510          */
2511         if (sigequalsets(&tsk->blocked, newset))
2512                 return;
2513 
2514         spin_lock_irq(&tsk->sighand->siglock);
2515         __set_task_blocked(tsk, newset);
2516         spin_unlock_irq(&tsk->sighand->siglock);
2517 }
2518 
2519 /*
2520  * This is also useful for kernel threads that want to temporarily
2521  * (or permanently) block certain signals.
2522  *
2523  * NOTE! Unlike the user-mode sys_sigprocmask(), the kernel
2524  * interface happily blocks "unblockable" signals like SIGKILL
2525  * and friends.
2526  */
2527 int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
2528 {
2529         struct task_struct *tsk = current;
2530         sigset_t newset;
2531 
2532         /* Lockless, only current can change ->blocked, never from irq */
2533         if (oldset)
2534                 *oldset = tsk->blocked;
2535 
2536         switch (how) {
2537         case SIG_BLOCK:
2538                 sigorsets(&newset, &tsk->blocked, set);
2539                 break;
2540         case SIG_UNBLOCK:
2541                 sigandnsets(&newset, &tsk->blocked, set);
2542                 break;
2543         case SIG_SETMASK:
2544                 newset = *set;
2545                 break;
2546         default:
2547                 return -EINVAL;
2548         }
2549 
2550         __set_current_blocked(&newset);
2551         return 0;
2552 }
2553 
2554 /**
2555  *  sys_rt_sigprocmask - change the list of currently blocked signals
2556  *  @how: whether to add, remove, or set signals
2557  *  @nset: stores pending signals
2558  *  @oset: previous value of signal mask if non-null
2559  *  @sigsetsize: size of sigset_t type
2560  */
2561 SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset,
2562                 sigset_t __user *, oset, size_t, sigsetsize)
2563 {
2564         sigset_t old_set, new_set;
2565         int error;
2566 
2567         /* XXX: Don't preclude handling different sized sigset_t's.  */
2568         if (sigsetsize != sizeof(sigset_t))
2569                 return -EINVAL;
2570 
2571         old_set = current->blocked;
2572 
2573         if (nset) {
2574                 if (copy_from_user(&new_set, nset, sizeof(sigset_t)))
2575                         return -EFAULT;
2576                 sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
2577 
2578                 error = sigprocmask(how, &new_set, NULL);
2579                 if (error)
2580                         return error;
2581         }
2582 
2583         if (oset) {
2584                 if (copy_to_user(oset, &old_set, sizeof(sigset_t)))
2585                         return -EFAULT;
2586         }
2587 
2588         return 0;
2589 }
2590 
2591 #ifdef CONFIG_COMPAT
2592 COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset,
2593                 compat_sigset_t __user *, oset, compat_size_t, sigsetsize)
2594 {
2595 #ifdef __BIG_ENDIAN
2596         sigset_t old_set = current->blocked;
2597 
2598         /* XXX: Don't preclude handling different sized sigset_t's.  */
2599         if (sigsetsize != sizeof(sigset_t))
2600                 return -EINVAL;
2601 
2602         if (nset) {
2603                 compat_sigset_t new32;
2604                 sigset_t new_set;
2605                 int error;
2606                 if (copy_from_user(&new32, nset, sizeof(compat_sigset_t)))
2607                         return -EFAULT;
2608 
2609                 sigset_from_compat(&new_set, &new32);
2610                 sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
2611 
2612                 error = sigprocmask(how, &new_set, NULL);
2613                 if (error)
2614                         return error;
2615         }
2616         if (oset) {
2617                 compat_sigset_t old32;
2618                 sigset_to_compat(&old32, &old_set);
2619                 if (copy_to_user(oset, &old32, sizeof(compat_sigset_t)))
2620                         return -EFAULT;
2621         }
2622         return 0;
2623 #else
2624         return sys_rt_sigprocmask(how, (sigset_t __user *)nset,
2625                                   (sigset_t __user *)oset, sigsetsize);
2626 #endif
2627 }
2628 #endif
2629 
2630 static int do_sigpending(void *set, unsigned long sigsetsize)
2631 {
2632         if (sigsetsize > sizeof(sigset_t))
2633                 return -EINVAL;
2634 
2635         spin_lock_irq(&current->sighand->siglock);
2636         sigorsets(set, &current->pending.signal,
2637                   &current->signal->shared_pending.signal);
2638         spin_unlock_irq(&current->sighand->siglock);
2639 
2640         /* Outside the lock because only this thread touches it.  */
2641         sigandsets(set, &current->blocked, set);
2642         return 0;
2643 }
2644 
2645 /**
2646  *  sys_rt_sigpending - examine a pending signal that has been raised
2647  *                      while blocked
2648  *  @uset: stores pending signals
2649  *  @sigsetsize: size of sigset_t type or larger
2650  */
2651 SYSCALL_DEFINE2(rt_sigpending, sigset_t __user *, uset, size_t, sigsetsize)
2652 {
2653         sigset_t set;
2654         int err = do_sigpending(&set, sigsetsize);
2655         if (!err && copy_to_user(uset, &set, sigsetsize))
2656                 err = -EFAULT;
2657         return err;
2658 }
2659 
2660 #ifdef CONFIG_COMPAT
2661 COMPAT_SYSCALL_DEFINE2(rt_sigpending, compat_sigset_t __user *, uset,
2662                 compat_size_t, sigsetsize)
2663 {
2664 #ifdef __BIG_ENDIAN
2665         sigset_t set;
2666         int err = do_sigpending(&set, sigsetsize);
2667         if (!err) {
2668                 compat_sigset_t set32;
2669                 sigset_to_compat(&set32, &set);
2670                 /* we can get here only if sigsetsize <= sizeof(set) */
2671                 if (copy_to_user(uset, &set32, sigsetsize))
2672                         err = -EFAULT;
2673         }
2674         return err;
2675 #else
2676         return sys_rt_sigpending((sigset_t __user *)uset, sigsetsize);
2677 #endif
2678 }
2679 #endif
2680 
2681 #ifndef HAVE_ARCH_COPY_SIGINFO_TO_USER
2682 
2683 int copy_siginfo_to_user(siginfo_t __user *to, const siginfo_t *from)
2684 {
2685         int err;
2686 
2687         if (!access_ok (VERIFY_WRITE, to, sizeof(siginfo_t)))
2688                 return -EFAULT;
2689         if (from->si_code < 0)
2690                 return __copy_to_user(to, from, sizeof(siginfo_t))
2691                         ? -EFAULT : 0;
2692         /*
2693          * If you change siginfo_t structure, please be sure
2694          * this code is fixed accordingly.
2695          * Please remember to update the signalfd_copyinfo() function
2696          * inside fs/signalfd.c too, in case siginfo_t changes.
2697          * It should never copy any pad contained in the structure
2698          * to avoid security leaks, but must copy the generic
2699          * 3 ints plus the relevant union member.
2700          */
2701         err = __put_user(from->si_signo, &to->si_signo);
2702         err |= __put_user(from->si_errno, &to->si_errno);
2703         err |= __put_user((short)from->si_code, &to->si_code);
2704         switch (from->si_code & __SI_MASK) {
2705         case __SI_KILL:
2706                 err |= __put_user(from->si_pid, &to->si_pid);
2707                 err |= __put_user(from->si_uid, &to->si_uid);
2708                 break;
2709         case __SI_TIMER:
2710                  err |= __put_user(from->si_tid, &to->si_tid);
2711                  err |= __put_user(from->si_overrun, &to->si_overrun);
2712                  err |= __put_user(from->si_ptr, &to->si_ptr);
2713                 break;
2714         case __SI_POLL:
2715                 err |= __put_user(from->si_band, &to->si_band);
2716                 err |= __put_user(from->si_fd, &to->si_fd);
2717                 break;
2718         case __SI_FAULT:
2719                 err |= __put_user(from->si_addr, &to->si_addr);
2720 #ifdef __ARCH_SI_TRAPNO
2721                 err |= __put_user(from->si_trapno, &to->si_trapno);
2722 #endif
2723 #ifdef BUS_MCEERR_AO
2724                 /*
2725                  * Other callers might not initialize the si_lsb field,
2726                  * so check explicitly for the right codes here.
2727                  */
2728                 if (from->si_signo == SIGBUS &&
2729                     (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO))
2730                         err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb);
2731 #endif
2732 #ifdef SEGV_BNDERR
2733                 if (from->si_signo == SIGSEGV && from->si_code == SEGV_BNDERR) {
2734                         err |= __put_user(from->si_lower, &to->si_lower);
2735                         err |= __put_user(from->si_upper, &to->si_upper);
2736                 }
2737 #endif
2738 #ifdef SEGV_PKUERR
2739                 if (from->si_signo == SIGSEGV && from->si_code == SEGV_PKUERR)
2740                         err |= __put_user(from->si_pkey, &to->si_pkey);
2741 #endif
2742                 break;
2743         case __SI_CHLD:
2744                 err |= __put_user(from->si_pid, &to->si_pid);
2745                 err |= __put_user(from->si_uid, &to->si_uid);
2746                 err |= __put_user(from->si_status, &to->si_status);
2747                 err |= __put_user(from->si_utime, &to->si_utime);
2748                 err |= __put_user(from->si_stime, &to->si_stime);
2749                 break;
2750         case __SI_RT: /* This is not generated by the kernel as of now. */
2751         case __SI_MESGQ: /* But this is */
2752                 err |= __put_user(from->si_pid, &to->si_pid);
2753                 err |= __put_user(from->si_uid, &to->si_uid);
2754                 err |= __put_user(from->si_ptr, &to->si_ptr);
2755                 break;
2756 #ifdef __ARCH_SIGSYS
2757         case __SI_SYS:
2758                 err |= __put_user(from->si_call_addr, &to->si_call_addr);
2759                 err |= __put_user(from->si_syscall, &to->si_syscall);
2760                 err |= __put_user(from->si_arch, &to->si_arch);
2761                 break;
2762 #endif
2763         default: /* this is just in case for now ... */
2764                 err |= __put_user(from->si_pid, &to->si_pid);
2765                 err |= __put_user(from->si_uid, &to->si_uid);
2766                 break;
2767         }
2768         return err;
2769 }
2770 
2771 #endif
2772 
2773 /**
2774  *  do_sigtimedwait - wait for queued signals specified in @which
2775  *  @which: queued signals to wait for
2776  *  @info: if non-null, the signal's siginfo is returned here
2777  *  @ts: upper bound on process time suspension
2778  */
2779 int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
2780                     const struct timespec *ts)
2781 {
2782         ktime_t *to = NULL, timeout = KTIME_MAX;
2783         struct task_struct *tsk = current;
2784         sigset_t mask = *which;
2785         int sig, ret = 0;
2786 
2787         if (ts) {
2788                 if (!timespec_valid(ts))
2789                         return -EINVAL;
2790                 timeout = timespec_to_ktime(*ts);
2791                 to = &timeout;
2792         }
2793 
2794         /*
2795          * Invert the set of allowed signals to get those we want to block.
2796          */
2797         sigdelsetmask(&mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
2798         signotset(&mask);
2799 
2800         spin_lock_irq(&tsk->sighand->siglock);
2801         sig = dequeue_signal(tsk, &mask, info);
2802         if (!sig && timeout) {
2803                 /*
2804                  * None ready, temporarily unblock those we're interested
2805                  * while we are sleeping in so that we'll be awakened when
2806                  * they arrive. Unblocking is always fine, we can avoid
2807                  * set_current_blocked().
2808                  */
2809                 tsk->real_blocked = tsk->blocked;
2810                 sigandsets(&tsk->blocked, &tsk->blocked, &mask);
2811                 recalc_sigpending();
2812                 spin_unlock_irq(&tsk->sighand->siglock);
2813 
2814                 __set_current_state(TASK_INTERRUPTIBLE);
2815                 ret = freezable_schedule_hrtimeout_range(to, tsk->timer_slack_ns,
2816                                                          HRTIMER_MODE_REL);
2817                 spin_lock_irq(&tsk->sighand->siglock);
2818                 __set_task_blocked(tsk, &tsk->real_blocked);
2819                 sigemptyset(&tsk->real_blocked);
2820                 sig = dequeue_signal(tsk, &mask, info);
2821         }
2822         spin_unlock_irq(&tsk->sighand->siglock);
2823 
2824         if (sig)
2825                 return sig;
2826         return ret ? -EINTR : -EAGAIN;
2827 }
2828 
2829 /**
2830  *  sys_rt_sigtimedwait - synchronously wait for queued signals specified
2831  *                      in @uthese
2832  *  @uthese: queued signals to wait for
2833  *  @uinfo: if non-null, the signal's siginfo is returned here
2834  *  @uts: upper bound on process time suspension
2835  *  @sigsetsize: size of sigset_t type
2836  */
2837 SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
2838                 siginfo_t __user *, uinfo, const struct timespec __user *, uts,
2839                 size_t, sigsetsize)
2840 {
2841         sigset_t these;
2842         struct timespec ts;
2843         siginfo_t info;
2844         int ret;
2845 
2846         /* XXX: Don't preclude handling different sized sigset_t's.  */
2847         if (sigsetsize != sizeof(sigset_t))
2848                 return -EINVAL;
2849 
2850         if (copy_from_user(&these, uthese, sizeof(these)))
2851                 return -EFAULT;
2852 
2853         if (uts) {
2854                 if (copy_from_user(&ts, uts, sizeof(ts)))
2855                         return -EFAULT;
2856         }
2857 
2858         ret = do_sigtimedwait(&these, &info, uts ? &ts : NULL);
2859 
2860         if (ret > 0 && uinfo) {
2861                 if (copy_siginfo_to_user(uinfo, &info))
2862                         ret = -EFAULT;
2863         }
2864 
2865         return ret;
2866 }
2867 
2868 /**
2869  *  sys_kill - send a signal to a process
2870  *  @pid: the PID of the process
2871  *  @sig: signal to be sent
2872  */
2873 SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
2874 {
2875         struct siginfo info;
2876         if (ccs_kill_permission(pid, sig))
2877                 return -EPERM;
2878 
2879         info.si_signo = sig;
2880         info.si_errno = 0;
2881         info.si_code = SI_USER;
2882         info.si_pid = task_tgid_vnr(current);
2883         info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
2884 
2885         return kill_something_info(sig, &info, pid);
2886 }
2887 
2888 static int
2889 do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info)
2890 {
2891         struct task_struct *p;
2892         int error = -ESRCH;
2893 
2894         rcu_read_lock();
2895         p = find_task_by_vpid(pid);
2896         if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
2897                 error = check_kill_permission(sig, info, p);
2898                 /*
2899                  * The null signal is a permissions and process existence
2900                  * probe.  No signal is actually delivered.
2901                  */
2902                 if (!error && sig) {
2903                         error = do_send_sig_info(sig, info, p, false);
2904                         /*
2905                          * If lock_task_sighand() failed we pretend the task
2906                          * dies after receiving the signal. The window is tiny,
2907                          * and the signal is private anyway.
2908                          */
2909                         if (unlikely(error == -ESRCH))
2910                                 error = 0;
2911                 }
2912         }
2913         rcu_read_unlock();
2914 
2915         return error;
2916 }
2917 
2918 static int do_tkill(pid_t tgid, pid_t pid, int sig)
2919 {
2920         struct siginfo info = {};
2921 
2922         info.si_signo = sig;
2923         info.si_errno = 0;
2924         info.si_code = SI_TKILL;
2925         info.si_pid = task_tgid_vnr(current);
2926         info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
2927 
2928         return do_send_specific(tgid, pid, sig, &info);
2929 }
2930 
2931 /**
2932  *  sys_tgkill - send signal to one specific thread
2933  *  @tgid: the thread group ID of the thread
2934  *  @pid: the PID of the thread
2935  *  @sig: signal to be sent
2936  *
2937  *  This syscall also checks the @tgid and returns -ESRCH even if the PID
2938  *  exists but it's not belonging to the target process anymore. This
2939  *  method solves the problem of threads exiting and PIDs getting reused.
2940  */
2941 SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig)
2942 {
2943         /* This is only valid for single tasks */
2944         if (pid <= 0 || tgid <= 0)
2945                 return -EINVAL;
2946         if (ccs_tgkill_permission(tgid, pid, sig))
2947                 return -EPERM;
2948 
2949         return do_tkill(tgid, pid, sig);
2950 }
2951 
2952 /**
2953  *  sys_tkill - send signal to one specific task
2954  *  @pid: the PID of the task
2955  *  @sig: signal to be sent
2956  *
2957  *  Send a signal to only one task, even if it's a CLONE_THREAD task.
2958  */
2959 SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
2960 {
2961         /* This is only valid for single tasks */
2962         if (pid <= 0)
2963                 return -EINVAL;
2964         if (ccs_tkill_permission(pid, sig))
2965                 return -EPERM;
2966 
2967         return do_tkill(0, pid, sig);
2968 }
2969 
2970 static int do_rt_sigqueueinfo(pid_t pid, int sig, siginfo_t *info)
2971 {
2972         /* Not even root can pretend to send signals from the kernel.
2973          * Nor can they impersonate a kill()/tgkill(), which adds source info.
2974          */
2975         if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
2976             (task_pid_vnr(current) != pid))
2977                 return -EPERM;
2978 
2979         info->si_signo = sig;
2980         if (ccs_sigqueue_permission(pid, sig))
2981                 return -EPERM;
2982 
2983         /* POSIX.1b doesn't mention process groups.  */
2984         return kill_proc_info(sig, info, pid);
2985 }
2986 
2987 /**
2988  *  sys_rt_sigqueueinfo - send signal information to a signal
2989  *  @pid: the PID of the thread
2990  *  @sig: signal to be sent
2991  *  @uinfo: signal info to be sent
2992  */
2993 SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
2994                 siginfo_t __user *, uinfo)
2995 {
2996         siginfo_t info;
2997         if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
2998                 return -EFAULT;
2999         return do_rt_sigqueueinfo(pid, sig, &info);
3000 }
3001 
3002 #ifdef CONFIG_COMPAT
3003 COMPAT_SYSCALL_DEFINE3(rt_sigqueueinfo,
3004                         compat_pid_t, pid,
3005                         int, sig,
3006                         struct compat_siginfo __user *, uinfo)
3007 {
3008         siginfo_t info = {};
3009         int ret = copy_siginfo_from_user32(&info, uinfo);
3010         if (unlikely(ret))
3011                 return ret;
3012         return do_rt_sigqueueinfo(pid, sig, &info);
3013 }
3014 #endif
3015 
3016 static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
3017 {
3018         /* This is only valid for single tasks */
3019         if (pid <= 0 || tgid <= 0)
3020                 return -EINVAL;
3021 
3022         /* Not even root can pretend to send signals from the kernel.
3023          * Nor can they impersonate a kill()/tgkill(), which adds source info.
3024          */
3025         if ((info->si_code >= 0 || info->si_code == SI_TKILL) &&
3026             (task_pid_vnr(current) != pid))
3027                 return -EPERM;
3028 
3029         info->si_signo = sig;
3030         if (ccs_tgsigqueue_permission(tgid, pid, sig))
3031                 return -EPERM;
3032 
3033         return do_send_specific(tgid, pid, sig, info);
3034 }
3035 
3036 SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig,
3037                 siginfo_t __user *, uinfo)
3038 {
3039         siginfo_t info;
3040 
3041         if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
3042                 return -EFAULT;
3043 
3044         return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
3045 }
3046 
3047 #ifdef CONFIG_COMPAT
3048 COMPAT_SYSCALL_DEFINE4(rt_tgsigqueueinfo,
3049                         compat_pid_t, tgid,
3050                         compat_pid_t, pid,
3051                         int, sig,
3052                         struct compat_siginfo __user *, uinfo)
3053 {
3054         siginfo_t info = {};
3055 
3056         if (copy_siginfo_from_user32(&info, uinfo))
3057                 return -EFAULT;
3058         return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
3059 }
3060 #endif
3061 
3062 /*
3063  * For kthreads only, must not be used if cloned with CLONE_SIGHAND
3064  */
3065 void kernel_sigaction(int sig, __sighandler_t action)
3066 {
3067         spin_lock_irq(&current->sighand->siglock);
3068         current->sighand->action[sig - 1].sa.sa_handler = action;
3069         if (action == SIG_IGN) {
3070                 sigset_t mask;
3071 
3072                 sigemptyset(&mask);
3073                 sigaddset(&mask, sig);
3074 
3075                 flush_sigqueue_mask(&mask, &current->signal->shared_pending);
3076                 flush_sigqueue_mask(&mask, &current->pending);
3077                 recalc_sigpending();
3078         }
3079         spin_unlock_irq(&current->sighand->siglock);
3080 }
3081 EXPORT_SYMBOL(kernel_sigaction);
3082 
3083 void __weak sigaction_compat_abi(struct k_sigaction *act,
3084                 struct k_sigaction *oact)
3085 {
3086 }
3087 
3088 int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
3089 {
3090         struct task_struct *p = current, *t;
3091         struct k_sigaction *k;
3092         sigset_t mask;
3093 
3094         if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
3095                 return -EINVAL;
3096 
3097         k = &p->sighand->action[sig-1];
3098 
3099         spin_lock_irq(&p->sighand->siglock);
3100         if (oact)
3101                 *oact = *k;
3102 
3103         sigaction_compat_abi(act, oact);
3104 
3105         if (act) {
3106                 sigdelsetmask(&act->sa.sa_mask,
3107                               sigmask(SIGKILL) | sigmask(SIGSTOP));
3108                 *k = *act;
3109                 /*
3110                  * POSIX 3.3.1.3:
3111                  *  "Setting a signal action to SIG_IGN for a signal that is
3112                  *   pending shall cause the pending signal to be discarded,
3113                  *   whether or not it is blocked."
3114                  *
3115                  *  "Setting a signal action to SIG_DFL for a signal that is
3116                  *   pending and whose default action is to ignore the signal
3117                  *   (for example, SIGCHLD), shall cause the pending signal to
3118                  *   be discarded, whether or not it is blocked"
3119                  */
3120                 if (sig_handler_ignored(sig_handler(p, sig), sig)) {
3121                         sigemptyset(&mask);
3122                         sigaddset(&mask, sig);
3123                         flush_sigqueue_mask(&mask, &p->signal->shared_pending);
3124                         for_each_thread(p, t)
3125                                 flush_sigqueue_mask(&mask, &t->pending);
3126                 }
3127         }
3128 
3129         spin_unlock_irq(&p->sighand->siglock);
3130         return 0;
3131 }
3132 
3133 static int
3134 do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long sp)
3135 {
3136         stack_t oss;
3137         int error;
3138 
3139         oss.ss_sp = (void __user *) current->sas_ss_sp;
3140         oss.ss_size = current->sas_ss_size;
3141         oss.ss_flags = sas_ss_flags(sp) |
3142                 (current->sas_ss_flags & SS_FLAG_BITS);
3143 
3144         if (uss) {
3145                 void __user *ss_sp;
3146                 size_t ss_size;
3147                 unsigned ss_flags;
3148                 int ss_mode;
3149 
3150                 error = -EFAULT;
3151                 if (!access_ok(VERIFY_READ, uss, sizeof(*uss)))
3152                         goto out;
3153                 error = __get_user(ss_sp, &uss->ss_sp) |
3154                         __get_user(ss_flags, &uss->ss_flags) |
3155                         __get_user(ss_size, &uss->ss_size);
3156                 if (error)
3157                         goto out;
3158 
3159                 error = -EPERM;
3160                 if (on_sig_stack(sp))
3161                         goto out;
3162 
3163                 ss_mode = ss_flags & ~SS_FLAG_BITS;
3164                 error = -EINVAL;
3165                 if (ss_mode != SS_DISABLE && ss_mode != SS_ONSTACK &&
3166                                 ss_mode != 0)
3167                         goto out;
3168 
3169                 if (ss_mode == SS_DISABLE) {
3170                         ss_size = 0;
3171                         ss_sp = NULL;
3172                 } else {
3173                         error = -ENOMEM;
3174                         if (ss_size < MINSIGSTKSZ)
3175                                 goto out;
3176                 }
3177 
3178                 current->sas_ss_sp = (unsigned long) ss_sp;
3179                 current->sas_ss_size = ss_size;
3180                 current->sas_ss_flags = ss_flags;
3181         }
3182 
3183         error = 0;
3184         if (uoss) {
3185                 error = -EFAULT;
3186                 if (!access_ok(VERIFY_WRITE, uoss, sizeof(*uoss)))
3187                         goto out;
3188                 error = __put_user(oss.ss_sp, &uoss->ss_sp) |
3189                         __put_user(oss.ss_size, &uoss->ss_size) |
3190                         __put_user(oss.ss_flags, &uoss->ss_flags);
3191         }
3192 
3193 out:
3194         return error;
3195 }
3196 SYSCALL_DEFINE2(sigaltstack,const stack_t __user *,uss, stack_t __user *,uoss)
3197 {
3198         return do_sigaltstack(uss, uoss, current_user_stack_pointer());
3199 }
3200 
3201 int restore_altstack(const stack_t __user *uss)
3202 {
3203         int err = do_sigaltstack(uss, NULL, current_user_stack_pointer());
3204         /* squash all but EFAULT for now */
3205         return err == -EFAULT ? err : 0;
3206 }
3207 
3208 int __save_altstack(stack_t __user *uss, unsigned long sp)
3209 {
3210         struct task_struct *t = current;
3211         int err = __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) |
3212                 __put_user(t->sas_ss_flags, &uss->ss_flags) |
3213                 __put_user(t->sas_ss_size, &uss->ss_size);
3214         if (err)
3215                 return err;
3216         if (t->sas_ss_flags & SS_AUTODISARM)
3217                 sas_ss_reset(t);
3218         return 0;
3219 }
3220 
3221 #ifdef CONFIG_COMPAT
3222 COMPAT_SYSCALL_DEFINE2(sigaltstack,
3223                         const compat_stack_t __user *, uss_ptr,
3224                         compat_stack_t __user *, uoss_ptr)
3225 {
3226         stack_t uss, uoss;
3227         int ret;
3228         mm_segment_t seg;
3229 
3230         if (uss_ptr) {
3231                 compat_stack_t uss32;
3232 
3233                 memset(&uss, 0, sizeof(stack_t));
3234                 if (copy_from_user(&uss32, uss_ptr, sizeof(compat_stack_t)))
3235                         return -EFAULT;
3236                 uss.ss_sp = compat_ptr(uss32.ss_sp);
3237                 uss.ss_flags = uss32.ss_flags;
3238                 uss.ss_size = uss32.ss_size;
3239         }
3240         seg = get_fs();
3241         set_fs(KERNEL_DS);
3242         ret = do_sigaltstack((stack_t __force __user *) (uss_ptr ? &uss : NULL),
3243                              (stack_t __force __user *) &uoss,
3244                              compat_user_stack_pointer());
3245         set_fs(seg);
3246         if (ret >= 0 && uoss_ptr)  {
3247                 if (!access_ok(VERIFY_WRITE, uoss_ptr, sizeof(compat_stack_t)) ||
3248                     __put_user(ptr_to_compat(uoss.ss_sp), &uoss_ptr->ss_sp) ||
3249                     __put_user(uoss.ss_flags, &uoss_ptr->ss_flags) ||
3250                     __put_user(uoss.ss_size, &uoss_ptr->ss_size))
3251                         ret = -EFAULT;
3252         }
3253         return ret;
3254 }
3255 
3256 int compat_restore_altstack(const compat_stack_t __user *uss)
3257 {
3258         int err = compat_sys_sigaltstack(uss, NULL);
3259         /* squash all but -EFAULT for now */
3260         return err == -EFAULT ? err : 0;
3261 }
3262 
3263 int __compat_save_altstack(compat_stack_t __user *uss, unsigned long sp)
3264 {
3265         int err;
3266         struct task_struct *t = current;
3267         err = __put_user(ptr_to_compat((void __user *)t->sas_ss_sp),
3268                          &uss->ss_sp) |
3269                 __put_user(t->sas_ss_flags, &uss->ss_flags) |
3270                 __put_user(t->sas_ss_size, &uss->ss_size);
3271         if (err)
3272                 return err;
3273         if (t->sas_ss_flags & SS_AUTODISARM)
3274                 sas_ss_reset(t);
3275         return 0;
3276 }
3277 #endif
3278 
3279 #ifdef __ARCH_WANT_SYS_SIGPENDING
3280 
3281 /**
3282  *  sys_sigpending - examine pending signals
3283  *  @set: where mask of pending signal is returned
3284  */
3285 SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set)
3286 {
3287         return sys_rt_sigpending((sigset_t __user *)set, sizeof(old_sigset_t)); 
3288 }
3289 
3290 #endif
3291 
3292 #ifdef __ARCH_WANT_SYS_SIGPROCMASK
3293 /**
3294  *  sys_sigprocmask - examine and change blocked signals
3295  *  @how: whether to add, remove, or set signals
3296  *  @nset: signals to add or remove (if non-null)
3297  *  @oset: previous value of signal mask if non-null
3298  *
3299  * Some platforms have their own version with special arguments;
3300  * others support only sys_rt_sigprocmask.
3301  */
3302 
3303 SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset,
3304                 old_sigset_t __user *, oset)
3305 {
3306         old_sigset_t old_set, new_set;
3307         sigset_t new_blocked;
3308 
3309         old_set = current->blocked.sig[0];
3310 
3311         if (nset) {
3312                 if (copy_from_user(&new_set, nset, sizeof(*nset)))
3313                         return -EFAULT;
3314 
3315                 new_blocked = current->blocked;
3316 
3317                 switch (how) {
3318                 case SIG_BLOCK:
3319                         sigaddsetmask(&new_blocked, new_set);
3320                         break;
3321                 case SIG_UNBLOCK:
3322                         sigdelsetmask(&new_blocked, new_set);
3323                         break;
3324                 case SIG_SETMASK:
3325                         new_blocked.sig[0] = new_set;
3326                         break;
3327                 default:
3328                         return -EINVAL;
3329                 }
3330 
3331                 set_current_blocked(&new_blocked);
3332         }
3333 
3334         if (oset) {
3335                 if (copy_to_user(oset, &old_set, sizeof(*oset)))
3336                         return -EFAULT;
3337         }
3338 
3339         return 0;
3340 }
3341 #endif /* __ARCH_WANT_SYS_SIGPROCMASK */
3342 
3343 #ifndef CONFIG_ODD_RT_SIGACTION
3344 /**
3345  *  sys_rt_sigaction - alter an action taken by a process
3346  *  @sig: signal to be sent
3347  *  @act: new sigaction
3348  *  @oact: used to save the previous sigaction
3349  *  @sigsetsize: size of sigset_t type
3350  */
3351 SYSCALL_DEFINE4(rt_sigaction, int, sig,
3352                 const struct sigaction __user *, act,
3353                 struct sigaction __user *, oact,
3354                 size_t, sigsetsize)
3355 {
3356         struct k_sigaction new_sa, old_sa;
3357         int ret = -EINVAL;
3358 
3359         /* XXX: Don't preclude handling different sized sigset_t's.  */
3360         if (sigsetsize != sizeof(sigset_t))
3361                 goto out;
3362 
3363         if (act) {
3364                 if (copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa)))
3365                         return -EFAULT;
3366         }
3367 
3368         ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
3369 
3370         if (!ret && oact) {
3371                 if (copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa)))
3372                         return -EFAULT;
3373         }
3374 out:
3375         return ret;
3376 }
3377 #ifdef CONFIG_COMPAT
3378 COMPAT_SYSCALL_DEFINE4(rt_sigaction, int, sig,
3379                 const struct compat_sigaction __user *, act,
3380                 struct compat_sigaction __user *, oact,
3381                 compat_size_t, sigsetsize)
3382 {
3383         struct k_sigaction new_ka, old_ka;
3384         compat_sigset_t mask;
3385 #ifdef __ARCH_HAS_SA_RESTORER
3386         compat_uptr_t restorer;
3387 #endif
3388         int ret;
3389 
3390         /* XXX: Don't preclude handling different sized sigset_t's.  */
3391         if (sigsetsize != sizeof(compat_sigset_t))
3392                 return -EINVAL;
3393 
3394         if (act) {
3395                 compat_uptr_t handler;
3396                 ret = get_user(handler, &act->sa_handler);
3397                 new_ka.sa.sa_handler = compat_ptr(handler);
3398 #ifdef __ARCH_HAS_SA_RESTORER
3399                 ret |= get_user(restorer, &act->sa_restorer);
3400                 new_ka.sa.sa_restorer = compat_ptr(restorer);
3401 #endif
3402                 ret |= copy_from_user(&mask, &act->sa_mask, sizeof(mask));
3403                 ret |= get_user(new_ka.sa.sa_flags, &act->sa_flags);
3404                 if (ret)
3405                         return -EFAULT;
3406                 sigset_from_compat(&new_ka.sa.sa_mask, &mask);
3407         }
3408 
3409         ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
3410         if (!ret && oact) {
3411                 sigset_to_compat(&mask, &old_ka.sa.sa_mask);
3412                 ret = put_user(ptr_to_compat(old_ka.sa.sa_handler), 
3413                                &oact->sa_handler);
3414                 ret |= copy_to_user(&oact->sa_mask, &mask, sizeof(mask));
3415                 ret |= put_user(old_ka.sa.sa_flags, &oact->sa_flags);
3416 #ifdef __ARCH_HAS_SA_RESTORER
3417                 ret |= put_user(ptr_to_compat(old_ka.sa.sa_restorer),
3418                                 &oact->sa_restorer);
3419 #endif
3420         }
3421         return ret;
3422 }
3423 #endif
3424 #endif /* !CONFIG_ODD_RT_SIGACTION */
3425 
3426 #ifdef CONFIG_OLD_SIGACTION
3427 SYSCALL_DEFINE3(sigaction, int, sig,
3428                 const struct old_sigaction __user *, act,
3429                 struct old_sigaction __user *, oact)
3430 {
3431         struct k_sigaction new_ka, old_ka;
3432         int ret;
3433 
3434         if (act) {
3435                 old_sigset_t mask;
3436                 if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
3437                     __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
3438                     __get_user(new_ka.sa.sa_restorer, &act->sa_restorer) ||
3439                     __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
3440                     __get_user(mask, &act->sa_mask))
3441                         return -EFAULT;
3442 #ifdef __ARCH_HAS_KA_RESTORER
3443                 new_ka.ka_restorer = NULL;
3444 #endif
3445                 siginitset(&new_ka.sa.sa_mask, mask);
3446         }
3447 
3448         ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
3449 
3450         if (!ret && oact) {
3451                 if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
3452                     __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
3453                     __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer) ||
3454                     __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
3455                     __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
3456                         return -EFAULT;
3457         }
3458 
3459         return ret;
3460 }
3461 #endif
3462 #ifdef CONFIG_COMPAT_OLD_SIGACTION
3463 COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
3464                 const struct compat_old_sigaction __user *, act,
3465                 struct compat_old_sigaction __user *, oact)
3466 {
3467         struct k_sigaction new_ka, old_ka;
3468         int ret;
3469         compat_old_sigset_t mask;
3470         compat_uptr_t handler, restorer;
3471 
3472         if (act) {
3473                 if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
3474                     __get_user(handler, &act->sa_handler) ||
3475                     __get_user(restorer, &act->sa_restorer) ||
3476                     __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
3477                     __get_user(mask, &act->sa_mask))
3478                         return -EFAULT;
3479 
3480 #ifdef __ARCH_HAS_KA_RESTORER
3481                 new_ka.ka_restorer = NULL;
3482 #endif
3483                 new_ka.sa.sa_handler = compat_ptr(handler);
3484                 new_ka.sa.sa_restorer = compat_ptr(restorer);
3485                 siginitset(&new_ka.sa.sa_mask, mask);
3486         }
3487 
3488         ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
3489 
3490         if (!ret && oact) {
3491                 if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
3492                     __put_user(ptr_to_compat(old_ka.sa.sa_handler),
3493                                &oact->sa_handler) ||
3494                     __put_user(ptr_to_compat(old_ka.sa.sa_restorer),
3495                                &oact->sa_restorer) ||
3496                     __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
3497                     __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
3498                         return -EFAULT;
3499         }
3500         return ret;
3501 }
3502 #endif
3503 
3504 #ifdef CONFIG_SGETMASK_SYSCALL
3505 
3506 /*
3507  * For backwards compatibility.  Functionality superseded by sigprocmask.
3508  */
3509 SYSCALL_DEFINE0(sgetmask)
3510 {
3511         /* SMP safe */
3512         return current->blocked.sig[0];
3513 }
3514 
3515 SYSCALL_DEFINE1(ssetmask, int, newmask)
3516 {
3517         int old = current->blocked.sig[0];
3518         sigset_t newset;
3519 
3520         siginitset(&newset, newmask);
3521         set_current_blocked(&newset);
3522 
3523         return old;
3524 }
3525 #endif /* CONFIG_SGETMASK_SYSCALL */
3526 
3527 #ifdef __ARCH_WANT_SYS_SIGNAL
3528 /*
3529  * For backwards compatibility.  Functionality superseded by sigaction.
3530  */
3531 SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
3532 {
3533         struct k_sigaction new_sa, old_sa;
3534         int ret;
3535 
3536         new_sa.sa.sa_handler = handler;
3537         new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK;
3538         sigemptyset(&new_sa.sa.sa_mask);
3539 
3540         ret = do_sigaction(sig, &new_sa, &old_sa);
3541 
3542         return ret ? ret : (unsigned long)old_sa.sa.sa_handler;
3543 }
3544 #endif /* __ARCH_WANT_SYS_SIGNAL */
3545 
3546 #ifdef __ARCH_WANT_SYS_PAUSE
3547 
3548 SYSCALL_DEFINE0(pause)
3549 {
3550         while (!signal_pending(current)) {
3551                 __set_current_state(TASK_INTERRUPTIBLE);
3552                 schedule();
3553         }
3554         return -ERESTARTNOHAND;
3555 }
3556 
3557 #endif
3558 
3559 static int sigsuspend(sigset_t *set)
3560 {
3561         current->saved_sigmask = current->blocked;
3562         set_current_blocked(set);
3563 
3564         while (!signal_pending(current)) {
3565                 __set_current_state(TASK_INTERRUPTIBLE);
3566                 schedule();
3567         }
3568         set_restore_sigmask();
3569         return -ERESTARTNOHAND;
3570 }
3571 
3572 /**
3573  *  sys_rt_sigsuspend - replace the signal mask for a value with the
3574  *      @unewset value until a signal is received
3575  *  @unewset: new signal mask value
3576  *  @sigsetsize: size of sigset_t type
3577  */
3578 SYSCALL_DEFINE2(rt_sigsuspend, sigset_t __user *, unewset, size_t, sigsetsize)
3579 {
3580         sigset_t newset;
3581 
3582         /* XXX: Don't preclude handling different sized sigset_t's.  */
3583         if (sigsetsize != sizeof(sigset_t))
3584                 return -EINVAL;
3585 
3586         if (copy_from_user(&newset, unewset, sizeof(newset)))
3587                 return -EFAULT;
3588         return sigsuspend(&newset);
3589 }
3590  
3591 #ifdef CONFIG_COMPAT
3592 COMPAT_SYSCALL_DEFINE2(rt_sigsuspend, compat_sigset_t __user *, unewset, compat_size_t, sigsetsize)
3593 {
3594 #ifdef __BIG_ENDIAN
3595         sigset_t newset;
3596         compat_sigset_t newset32;
3597 
3598         /* XXX: Don't preclude handling different sized sigset_t's.  */
3599         if (sigsetsize != sizeof(sigset_t))
3600                 return -EINVAL;
3601 
3602         if (copy_from_user(&newset32, unewset, sizeof(compat_sigset_t)))
3603                 return -EFAULT;
3604         sigset_from_compat(&newset, &newset32);
3605         return sigsuspend(&newset);
3606 #else
3607         /* on little-endian bitmaps don't care about granularity */
3608         return sys_rt_sigsuspend((sigset_t __user *)unewset, sigsetsize);
3609 #endif
3610 }
3611 #endif
3612 
3613 #ifdef CONFIG_OLD_SIGSUSPEND
3614 SYSCALL_DEFINE1(sigsuspend, old_sigset_t, mask)
3615 {
3616         sigset_t blocked;
3617         siginitset(&blocked, mask);
3618         return sigsuspend(&blocked);
3619 }
3620 #endif
3621 #ifdef CONFIG_OLD_SIGSUSPEND3
3622 SYSCALL_DEFINE3(sigsuspend, int, unused1, int, unused2, old_sigset_t, mask)
3623 {
3624         sigset_t blocked;
3625         siginitset(&blocked, mask);
3626         return sigsuspend(&blocked);
3627 }
3628 #endif
3629 
3630 __weak const char *arch_vma_name(struct vm_area_struct *vma)
3631 {
3632         return NULL;
3633 }
3634 
3635 void __init signals_init(void)
3636 {
3637         /* If this check fails, the __ARCH_SI_PREAMBLE_SIZE value is wrong! */
3638         BUILD_BUG_ON(__ARCH_SI_PREAMBLE_SIZE
3639                 != offsetof(struct siginfo, _sifields._pad));
3640 
3641         sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
3642 }
3643 
3644 #ifdef CONFIG_KGDB_KDB
3645 #include <linux/kdb.h>
3646 /*
3647  * kdb_send_sig_info - Allows kdb to send signals without exposing
3648  * signal internals.  This function checks if the required locks are
3649  * available before calling the main signal code, to avoid kdb
3650  * deadlocks.
3651  */
3652 void
3653 kdb_send_sig_info(struct task_struct *t, struct siginfo *info)
3654 {
3655         static struct task_struct *kdb_prev_t;
3656         int sig, new_t;
3657         if (!spin_trylock(&t->sighand->siglock)) {
3658                 kdb_printf("Can't do kill command now.\n"
3659                            "The sigmask lock is held somewhere else in "
3660                            "kernel, try again later\n");
3661                 return;
3662         }
3663         spin_unlock(&t->sighand->siglock);
3664         new_t = kdb_prev_t != t;
3665         kdb_prev_t = t;
3666         if (t->state != TASK_RUNNING && new_t) {
3667                 kdb_printf("Process is not RUNNING, sending a signal from "
3668                            "kdb risks deadlock\n"
3669                            "on the run queue locks. "
3670                            "The signal has _not_ been sent.\n"
3671                            "Reissue the kill command if you want to risk "
3672                            "the deadlock.\n");
3673                 return;
3674         }
3675         sig = info->si_signo;
3676         if (send_sig_info(sig, info, t))
3677                 kdb_printf("Fail to deliver Signal %d to process %d.\n",
3678                            sig, t->pid);
3679         else
3680                 kdb_printf("Signal %d is sent to process %d.\n", sig, t->pid);
3681 }
3682 #endif  /* CONFIG_KGDB_KDB */
3683 

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