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TOMOYO Linux Cross Reference
Linux/fs/coredump.c

Version: ~ [ linux-5.12-rc7 ] ~ [ linux-5.11.13 ] ~ [ linux-5.10.29 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.111 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.186 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.230 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.266 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.266 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 // SPDX-License-Identifier: GPL-2.0
  2 #include <linux/slab.h>
  3 #include <linux/file.h>
  4 #include <linux/fdtable.h>
  5 #include <linux/freezer.h>
  6 #include <linux/mm.h>
  7 #include <linux/stat.h>
  8 #include <linux/fcntl.h>
  9 #include <linux/swap.h>
 10 #include <linux/ctype.h>
 11 #include <linux/string.h>
 12 #include <linux/init.h>
 13 #include <linux/pagemap.h>
 14 #include <linux/perf_event.h>
 15 #include <linux/highmem.h>
 16 #include <linux/spinlock.h>
 17 #include <linux/key.h>
 18 #include <linux/personality.h>
 19 #include <linux/binfmts.h>
 20 #include <linux/coredump.h>
 21 #include <linux/sched/coredump.h>
 22 #include <linux/sched/signal.h>
 23 #include <linux/sched/task_stack.h>
 24 #include <linux/utsname.h>
 25 #include <linux/pid_namespace.h>
 26 #include <linux/module.h>
 27 #include <linux/namei.h>
 28 #include <linux/mount.h>
 29 #include <linux/security.h>
 30 #include <linux/syscalls.h>
 31 #include <linux/tsacct_kern.h>
 32 #include <linux/cn_proc.h>
 33 #include <linux/audit.h>
 34 #include <linux/tracehook.h>
 35 #include <linux/kmod.h>
 36 #include <linux/fsnotify.h>
 37 #include <linux/fs_struct.h>
 38 #include <linux/pipe_fs_i.h>
 39 #include <linux/oom.h>
 40 #include <linux/compat.h>
 41 #include <linux/fs.h>
 42 #include <linux/path.h>
 43 #include <linux/timekeeping.h>
 44 
 45 #include <linux/uaccess.h>
 46 #include <asm/mmu_context.h>
 47 #include <asm/tlb.h>
 48 #include <asm/exec.h>
 49 
 50 #include <trace/events/task.h>
 51 #include "internal.h"
 52 
 53 #include <trace/events/sched.h>
 54 
 55 int core_uses_pid;
 56 unsigned int core_pipe_limit;
 57 char core_pattern[CORENAME_MAX_SIZE] = "core";
 58 static int core_name_size = CORENAME_MAX_SIZE;
 59 
 60 struct core_name {
 61         char *corename;
 62         int used, size;
 63 };
 64 
 65 /* The maximal length of core_pattern is also specified in sysctl.c */
 66 
 67 static int expand_corename(struct core_name *cn, int size)
 68 {
 69         char *corename = krealloc(cn->corename, size, GFP_KERNEL);
 70 
 71         if (!corename)
 72                 return -ENOMEM;
 73 
 74         if (size > core_name_size) /* racy but harmless */
 75                 core_name_size = size;
 76 
 77         cn->size = ksize(corename);
 78         cn->corename = corename;
 79         return 0;
 80 }
 81 
 82 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
 83                                      va_list arg)
 84 {
 85         int free, need;
 86         va_list arg_copy;
 87 
 88 again:
 89         free = cn->size - cn->used;
 90 
 91         va_copy(arg_copy, arg);
 92         need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
 93         va_end(arg_copy);
 94 
 95         if (need < free) {
 96                 cn->used += need;
 97                 return 0;
 98         }
 99 
100         if (!expand_corename(cn, cn->size + need - free + 1))
101                 goto again;
102 
103         return -ENOMEM;
104 }
105 
106 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
107 {
108         va_list arg;
109         int ret;
110 
111         va_start(arg, fmt);
112         ret = cn_vprintf(cn, fmt, arg);
113         va_end(arg);
114 
115         return ret;
116 }
117 
118 static __printf(2, 3)
119 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
120 {
121         int cur = cn->used;
122         va_list arg;
123         int ret;
124 
125         va_start(arg, fmt);
126         ret = cn_vprintf(cn, fmt, arg);
127         va_end(arg);
128 
129         if (ret == 0) {
130                 /*
131                  * Ensure that this coredump name component can't cause the
132                  * resulting corefile path to consist of a ".." or ".".
133                  */
134                 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
135                                 (cn->used - cur == 2 && cn->corename[cur] == '.'
136                                 && cn->corename[cur+1] == '.'))
137                         cn->corename[cur] = '!';
138 
139                 /*
140                  * Empty names are fishy and could be used to create a "//" in a
141                  * corefile name, causing the coredump to happen one directory
142                  * level too high. Enforce that all components of the core
143                  * pattern are at least one character long.
144                  */
145                 if (cn->used == cur)
146                         ret = cn_printf(cn, "!");
147         }
148 
149         for (; cur < cn->used; ++cur) {
150                 if (cn->corename[cur] == '/')
151                         cn->corename[cur] = '!';
152         }
153         return ret;
154 }
155 
156 static int cn_print_exe_file(struct core_name *cn)
157 {
158         struct file *exe_file;
159         char *pathbuf, *path;
160         int ret;
161 
162         exe_file = get_mm_exe_file(current->mm);
163         if (!exe_file)
164                 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
165 
166         pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
167         if (!pathbuf) {
168                 ret = -ENOMEM;
169                 goto put_exe_file;
170         }
171 
172         path = file_path(exe_file, pathbuf, PATH_MAX);
173         if (IS_ERR(path)) {
174                 ret = PTR_ERR(path);
175                 goto free_buf;
176         }
177 
178         ret = cn_esc_printf(cn, "%s", path);
179 
180 free_buf:
181         kfree(pathbuf);
182 put_exe_file:
183         fput(exe_file);
184         return ret;
185 }
186 
187 /* format_corename will inspect the pattern parameter, and output a
188  * name into corename, which must have space for at least
189  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
190  */
191 static int format_corename(struct core_name *cn, struct coredump_params *cprm,
192                            size_t **argv, int *argc)
193 {
194         const struct cred *cred = current_cred();
195         const char *pat_ptr = core_pattern;
196         int ispipe = (*pat_ptr == '|');
197         bool was_space = false;
198         int pid_in_pattern = 0;
199         int err = 0;
200 
201         cn->used = 0;
202         cn->corename = NULL;
203         if (expand_corename(cn, core_name_size))
204                 return -ENOMEM;
205         cn->corename[0] = '\0';
206 
207         if (ispipe) {
208                 int argvs = sizeof(core_pattern) / 2;
209                 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
210                 if (!(*argv))
211                         return -ENOMEM;
212                 (*argv)[(*argc)++] = 0;
213                 ++pat_ptr;
214                 if (!(*pat_ptr))
215                         return -ENOMEM;
216         }
217 
218         /* Repeat as long as we have more pattern to process and more output
219            space */
220         while (*pat_ptr) {
221                 /*
222                  * Split on spaces before doing template expansion so that
223                  * %e and %E don't get split if they have spaces in them
224                  */
225                 if (ispipe) {
226                         if (isspace(*pat_ptr)) {
227                                 was_space = true;
228                                 pat_ptr++;
229                                 continue;
230                         } else if (was_space) {
231                                 was_space = false;
232                                 err = cn_printf(cn, "%c", '\0');
233                                 if (err)
234                                         return err;
235                                 (*argv)[(*argc)++] = cn->used;
236                         }
237                 }
238                 if (*pat_ptr != '%') {
239                         err = cn_printf(cn, "%c", *pat_ptr++);
240                 } else {
241                         switch (*++pat_ptr) {
242                         /* single % at the end, drop that */
243                         case 0:
244                                 goto out;
245                         /* Double percent, output one percent */
246                         case '%':
247                                 err = cn_printf(cn, "%c", '%');
248                                 break;
249                         /* pid */
250                         case 'p':
251                                 pid_in_pattern = 1;
252                                 err = cn_printf(cn, "%d",
253                                               task_tgid_vnr(current));
254                                 break;
255                         /* global pid */
256                         case 'P':
257                                 err = cn_printf(cn, "%d",
258                                               task_tgid_nr(current));
259                                 break;
260                         case 'i':
261                                 err = cn_printf(cn, "%d",
262                                               task_pid_vnr(current));
263                                 break;
264                         case 'I':
265                                 err = cn_printf(cn, "%d",
266                                               task_pid_nr(current));
267                                 break;
268                         /* uid */
269                         case 'u':
270                                 err = cn_printf(cn, "%u",
271                                                 from_kuid(&init_user_ns,
272                                                           cred->uid));
273                                 break;
274                         /* gid */
275                         case 'g':
276                                 err = cn_printf(cn, "%u",
277                                                 from_kgid(&init_user_ns,
278                                                           cred->gid));
279                                 break;
280                         case 'd':
281                                 err = cn_printf(cn, "%d",
282                                         __get_dumpable(cprm->mm_flags));
283                                 break;
284                         /* signal that caused the coredump */
285                         case 's':
286                                 err = cn_printf(cn, "%d",
287                                                 cprm->siginfo->si_signo);
288                                 break;
289                         /* UNIX time of coredump */
290                         case 't': {
291                                 time64_t time;
292 
293                                 time = ktime_get_real_seconds();
294                                 err = cn_printf(cn, "%lld", time);
295                                 break;
296                         }
297                         /* hostname */
298                         case 'h':
299                                 down_read(&uts_sem);
300                                 err = cn_esc_printf(cn, "%s",
301                                               utsname()->nodename);
302                                 up_read(&uts_sem);
303                                 break;
304                         /* executable */
305                         case 'e':
306                                 err = cn_esc_printf(cn, "%s", current->comm);
307                                 break;
308                         case 'E':
309                                 err = cn_print_exe_file(cn);
310                                 break;
311                         /* core limit size */
312                         case 'c':
313                                 err = cn_printf(cn, "%lu",
314                                               rlimit(RLIMIT_CORE));
315                                 break;
316                         default:
317                                 break;
318                         }
319                         ++pat_ptr;
320                 }
321 
322                 if (err)
323                         return err;
324         }
325 
326 out:
327         /* Backward compatibility with core_uses_pid:
328          *
329          * If core_pattern does not include a %p (as is the default)
330          * and core_uses_pid is set, then .%pid will be appended to
331          * the filename. Do not do this for piped commands. */
332         if (!ispipe && !pid_in_pattern && core_uses_pid) {
333                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
334                 if (err)
335                         return err;
336         }
337         return ispipe;
338 }
339 
340 static int zap_process(struct task_struct *start, int exit_code, int flags)
341 {
342         struct task_struct *t;
343         int nr = 0;
344 
345         /* ignore all signals except SIGKILL, see prepare_signal() */
346         start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
347         start->signal->group_exit_code = exit_code;
348         start->signal->group_stop_count = 0;
349 
350         for_each_thread(start, t) {
351                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
352                 if (t != current && t->mm) {
353                         sigaddset(&t->pending.signal, SIGKILL);
354                         signal_wake_up(t, 1);
355                         nr++;
356                 }
357         }
358 
359         return nr;
360 }
361 
362 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
363                         struct core_state *core_state, int exit_code)
364 {
365         struct task_struct *g, *p;
366         unsigned long flags;
367         int nr = -EAGAIN;
368 
369         spin_lock_irq(&tsk->sighand->siglock);
370         if (!signal_group_exit(tsk->signal)) {
371                 mm->core_state = core_state;
372                 tsk->signal->group_exit_task = tsk;
373                 nr = zap_process(tsk, exit_code, 0);
374                 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
375         }
376         spin_unlock_irq(&tsk->sighand->siglock);
377         if (unlikely(nr < 0))
378                 return nr;
379 
380         tsk->flags |= PF_DUMPCORE;
381         if (atomic_read(&mm->mm_users) == nr + 1)
382                 goto done;
383         /*
384          * We should find and kill all tasks which use this mm, and we should
385          * count them correctly into ->nr_threads. We don't take tasklist
386          * lock, but this is safe wrt:
387          *
388          * fork:
389          *      None of sub-threads can fork after zap_process(leader). All
390          *      processes which were created before this point should be
391          *      visible to zap_threads() because copy_process() adds the new
392          *      process to the tail of init_task.tasks list, and lock/unlock
393          *      of ->siglock provides a memory barrier.
394          *
395          * do_exit:
396          *      The caller holds mm->mmap_sem. This means that the task which
397          *      uses this mm can't pass exit_mm(), so it can't exit or clear
398          *      its ->mm.
399          *
400          * de_thread:
401          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
402          *      we must see either old or new leader, this does not matter.
403          *      However, it can change p->sighand, so lock_task_sighand(p)
404          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
405          *      it can't fail.
406          *
407          *      Note also that "g" can be the old leader with ->mm == NULL
408          *      and already unhashed and thus removed from ->thread_group.
409          *      This is OK, __unhash_process()->list_del_rcu() does not
410          *      clear the ->next pointer, we will find the new leader via
411          *      next_thread().
412          */
413         rcu_read_lock();
414         for_each_process(g) {
415                 if (g == tsk->group_leader)
416                         continue;
417                 if (g->flags & PF_KTHREAD)
418                         continue;
419 
420                 for_each_thread(g, p) {
421                         if (unlikely(!p->mm))
422                                 continue;
423                         if (unlikely(p->mm == mm)) {
424                                 lock_task_sighand(p, &flags);
425                                 nr += zap_process(p, exit_code,
426                                                         SIGNAL_GROUP_EXIT);
427                                 unlock_task_sighand(p, &flags);
428                         }
429                         break;
430                 }
431         }
432         rcu_read_unlock();
433 done:
434         atomic_set(&core_state->nr_threads, nr);
435         return nr;
436 }
437 
438 static int coredump_wait(int exit_code, struct core_state *core_state)
439 {
440         struct task_struct *tsk = current;
441         struct mm_struct *mm = tsk->mm;
442         int core_waiters = -EBUSY;
443 
444         init_completion(&core_state->startup);
445         core_state->dumper.task = tsk;
446         core_state->dumper.next = NULL;
447 
448         if (down_write_killable(&mm->mmap_sem))
449                 return -EINTR;
450 
451         if (!mm->core_state)
452                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
453         up_write(&mm->mmap_sem);
454 
455         if (core_waiters > 0) {
456                 struct core_thread *ptr;
457 
458                 freezer_do_not_count();
459                 wait_for_completion(&core_state->startup);
460                 freezer_count();
461                 /*
462                  * Wait for all the threads to become inactive, so that
463                  * all the thread context (extended register state, like
464                  * fpu etc) gets copied to the memory.
465                  */
466                 ptr = core_state->dumper.next;
467                 while (ptr != NULL) {
468                         wait_task_inactive(ptr->task, 0);
469                         ptr = ptr->next;
470                 }
471         }
472 
473         return core_waiters;
474 }
475 
476 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
477 {
478         struct core_thread *curr, *next;
479         struct task_struct *task;
480 
481         spin_lock_irq(&current->sighand->siglock);
482         if (core_dumped && !__fatal_signal_pending(current))
483                 current->signal->group_exit_code |= 0x80;
484         current->signal->group_exit_task = NULL;
485         current->signal->flags = SIGNAL_GROUP_EXIT;
486         spin_unlock_irq(&current->sighand->siglock);
487 
488         next = mm->core_state->dumper.next;
489         while ((curr = next) != NULL) {
490                 next = curr->next;
491                 task = curr->task;
492                 /*
493                  * see exit_mm(), curr->task must not see
494                  * ->task == NULL before we read ->next.
495                  */
496                 smp_mb();
497                 curr->task = NULL;
498                 wake_up_process(task);
499         }
500 
501         mm->core_state = NULL;
502 }
503 
504 static bool dump_interrupted(void)
505 {
506         /*
507          * SIGKILL or freezing() interrupt the coredumping. Perhaps we
508          * can do try_to_freeze() and check __fatal_signal_pending(),
509          * but then we need to teach dump_write() to restart and clear
510          * TIF_SIGPENDING.
511          */
512         return signal_pending(current);
513 }
514 
515 static void wait_for_dump_helpers(struct file *file)
516 {
517         struct pipe_inode_info *pipe = file->private_data;
518 
519         pipe_lock(pipe);
520         pipe->readers++;
521         pipe->writers--;
522         wake_up_interruptible_sync(&pipe->rd_wait);
523         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
524         pipe_unlock(pipe);
525 
526         /*
527          * We actually want wait_event_freezable() but then we need
528          * to clear TIF_SIGPENDING and improve dump_interrupted().
529          */
530         wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
531 
532         pipe_lock(pipe);
533         pipe->readers--;
534         pipe->writers++;
535         pipe_unlock(pipe);
536 }
537 
538 /*
539  * umh_pipe_setup
540  * helper function to customize the process used
541  * to collect the core in userspace.  Specifically
542  * it sets up a pipe and installs it as fd 0 (stdin)
543  * for the process.  Returns 0 on success, or
544  * PTR_ERR on failure.
545  * Note that it also sets the core limit to 1.  This
546  * is a special value that we use to trap recursive
547  * core dumps
548  */
549 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
550 {
551         struct file *files[2];
552         struct coredump_params *cp = (struct coredump_params *)info->data;
553         int err = create_pipe_files(files, 0);
554         if (err)
555                 return err;
556 
557         cp->file = files[1];
558 
559         err = replace_fd(0, files[0], 0);
560         fput(files[0]);
561         /* and disallow core files too */
562         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
563 
564         return err;
565 }
566 
567 void do_coredump(const kernel_siginfo_t *siginfo)
568 {
569         struct core_state core_state;
570         struct core_name cn;
571         struct mm_struct *mm = current->mm;
572         struct linux_binfmt * binfmt;
573         const struct cred *old_cred;
574         struct cred *cred;
575         int retval = 0;
576         int ispipe;
577         size_t *argv = NULL;
578         int argc = 0;
579         struct files_struct *displaced;
580         /* require nonrelative corefile path and be extra careful */
581         bool need_suid_safe = false;
582         bool core_dumped = false;
583         static atomic_t core_dump_count = ATOMIC_INIT(0);
584         struct coredump_params cprm = {
585                 .siginfo = siginfo,
586                 .regs = signal_pt_regs(),
587                 .limit = rlimit(RLIMIT_CORE),
588                 /*
589                  * We must use the same mm->flags while dumping core to avoid
590                  * inconsistency of bit flags, since this flag is not protected
591                  * by any locks.
592                  */
593                 .mm_flags = mm->flags,
594         };
595 
596         audit_core_dumps(siginfo->si_signo);
597 
598         binfmt = mm->binfmt;
599         if (!binfmt || !binfmt->core_dump)
600                 goto fail;
601         if (!__get_dumpable(cprm.mm_flags))
602                 goto fail;
603 
604         cred = prepare_creds();
605         if (!cred)
606                 goto fail;
607         /*
608          * We cannot trust fsuid as being the "true" uid of the process
609          * nor do we know its entire history. We only know it was tainted
610          * so we dump it as root in mode 2, and only into a controlled
611          * environment (pipe handler or fully qualified path).
612          */
613         if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
614                 /* Setuid core dump mode */
615                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
616                 need_suid_safe = true;
617         }
618 
619         retval = coredump_wait(siginfo->si_signo, &core_state);
620         if (retval < 0)
621                 goto fail_creds;
622 
623         old_cred = override_creds(cred);
624 
625         ispipe = format_corename(&cn, &cprm, &argv, &argc);
626 
627         if (ispipe) {
628                 int argi;
629                 int dump_count;
630                 char **helper_argv;
631                 struct subprocess_info *sub_info;
632 
633                 if (ispipe < 0) {
634                         printk(KERN_WARNING "format_corename failed\n");
635                         printk(KERN_WARNING "Aborting core\n");
636                         goto fail_unlock;
637                 }
638 
639                 if (cprm.limit == 1) {
640                         /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
641                          *
642                          * Normally core limits are irrelevant to pipes, since
643                          * we're not writing to the file system, but we use
644                          * cprm.limit of 1 here as a special value, this is a
645                          * consistent way to catch recursive crashes.
646                          * We can still crash if the core_pattern binary sets
647                          * RLIM_CORE = !1, but it runs as root, and can do
648                          * lots of stupid things.
649                          *
650                          * Note that we use task_tgid_vnr here to grab the pid
651                          * of the process group leader.  That way we get the
652                          * right pid if a thread in a multi-threaded
653                          * core_pattern process dies.
654                          */
655                         printk(KERN_WARNING
656                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
657                                 task_tgid_vnr(current), current->comm);
658                         printk(KERN_WARNING "Aborting core\n");
659                         goto fail_unlock;
660                 }
661                 cprm.limit = RLIM_INFINITY;
662 
663                 dump_count = atomic_inc_return(&core_dump_count);
664                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
665                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
666                                task_tgid_vnr(current), current->comm);
667                         printk(KERN_WARNING "Skipping core dump\n");
668                         goto fail_dropcount;
669                 }
670 
671                 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
672                                             GFP_KERNEL);
673                 if (!helper_argv) {
674                         printk(KERN_WARNING "%s failed to allocate memory\n",
675                                __func__);
676                         goto fail_dropcount;
677                 }
678                 for (argi = 0; argi < argc; argi++)
679                         helper_argv[argi] = cn.corename + argv[argi];
680                 helper_argv[argi] = NULL;
681 
682                 retval = -ENOMEM;
683                 sub_info = call_usermodehelper_setup(helper_argv[0],
684                                                 helper_argv, NULL, GFP_KERNEL,
685                                                 umh_pipe_setup, NULL, &cprm);
686                 if (sub_info)
687                         retval = call_usermodehelper_exec(sub_info,
688                                                           UMH_WAIT_EXEC);
689 
690                 kfree(helper_argv);
691                 if (retval) {
692                         printk(KERN_INFO "Core dump to |%s pipe failed\n",
693                                cn.corename);
694                         goto close_fail;
695                 }
696         } else {
697                 struct inode *inode;
698                 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
699                                  O_LARGEFILE | O_EXCL;
700 
701                 if (cprm.limit < binfmt->min_coredump)
702                         goto fail_unlock;
703 
704                 if (need_suid_safe && cn.corename[0] != '/') {
705                         printk(KERN_WARNING "Pid %d(%s) can only dump core "\
706                                 "to fully qualified path!\n",
707                                 task_tgid_vnr(current), current->comm);
708                         printk(KERN_WARNING "Skipping core dump\n");
709                         goto fail_unlock;
710                 }
711 
712                 /*
713                  * Unlink the file if it exists unless this is a SUID
714                  * binary - in that case, we're running around with root
715                  * privs and don't want to unlink another user's coredump.
716                  */
717                 if (!need_suid_safe) {
718                         /*
719                          * If it doesn't exist, that's fine. If there's some
720                          * other problem, we'll catch it at the filp_open().
721                          */
722                         do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
723                 }
724 
725                 /*
726                  * There is a race between unlinking and creating the
727                  * file, but if that causes an EEXIST here, that's
728                  * fine - another process raced with us while creating
729                  * the corefile, and the other process won. To userspace,
730                  * what matters is that at least one of the two processes
731                  * writes its coredump successfully, not which one.
732                  */
733                 if (need_suid_safe) {
734                         /*
735                          * Using user namespaces, normal user tasks can change
736                          * their current->fs->root to point to arbitrary
737                          * directories. Since the intention of the "only dump
738                          * with a fully qualified path" rule is to control where
739                          * coredumps may be placed using root privileges,
740                          * current->fs->root must not be used. Instead, use the
741                          * root directory of init_task.
742                          */
743                         struct path root;
744 
745                         task_lock(&init_task);
746                         get_fs_root(init_task.fs, &root);
747                         task_unlock(&init_task);
748                         cprm.file = file_open_root(root.dentry, root.mnt,
749                                 cn.corename, open_flags, 0600);
750                         path_put(&root);
751                 } else {
752                         cprm.file = filp_open(cn.corename, open_flags, 0600);
753                 }
754                 if (IS_ERR(cprm.file))
755                         goto fail_unlock;
756 
757                 inode = file_inode(cprm.file);
758                 if (inode->i_nlink > 1)
759                         goto close_fail;
760                 if (d_unhashed(cprm.file->f_path.dentry))
761                         goto close_fail;
762                 /*
763                  * AK: actually i see no reason to not allow this for named
764                  * pipes etc, but keep the previous behaviour for now.
765                  */
766                 if (!S_ISREG(inode->i_mode))
767                         goto close_fail;
768                 /*
769                  * Don't dump core if the filesystem changed owner or mode
770                  * of the file during file creation. This is an issue when
771                  * a process dumps core while its cwd is e.g. on a vfat
772                  * filesystem.
773                  */
774                 if (!uid_eq(inode->i_uid, current_fsuid()))
775                         goto close_fail;
776                 if ((inode->i_mode & 0677) != 0600)
777                         goto close_fail;
778                 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
779                         goto close_fail;
780                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
781                         goto close_fail;
782         }
783 
784         /* get us an unshared descriptor table; almost always a no-op */
785         retval = unshare_files(&displaced);
786         if (retval)
787                 goto close_fail;
788         if (displaced)
789                 put_files_struct(displaced);
790         if (!dump_interrupted()) {
791                 /*
792                  * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
793                  * have this set to NULL.
794                  */
795                 if (!cprm.file) {
796                         pr_info("Core dump to |%s disabled\n", cn.corename);
797                         goto close_fail;
798                 }
799                 file_start_write(cprm.file);
800                 core_dumped = binfmt->core_dump(&cprm);
801                 file_end_write(cprm.file);
802         }
803         if (ispipe && core_pipe_limit)
804                 wait_for_dump_helpers(cprm.file);
805 close_fail:
806         if (cprm.file)
807                 filp_close(cprm.file, NULL);
808 fail_dropcount:
809         if (ispipe)
810                 atomic_dec(&core_dump_count);
811 fail_unlock:
812         kfree(argv);
813         kfree(cn.corename);
814         coredump_finish(mm, core_dumped);
815         revert_creds(old_cred);
816 fail_creds:
817         put_cred(cred);
818 fail:
819         return;
820 }
821 
822 /*
823  * Core dumping helper functions.  These are the only things you should
824  * do on a core-file: use only these functions to write out all the
825  * necessary info.
826  */
827 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
828 {
829         struct file *file = cprm->file;
830         loff_t pos = file->f_pos;
831         ssize_t n;
832         if (cprm->written + nr > cprm->limit)
833                 return 0;
834         while (nr) {
835                 if (dump_interrupted())
836                         return 0;
837                 n = __kernel_write(file, addr, nr, &pos);
838                 if (n <= 0)
839                         return 0;
840                 file->f_pos = pos;
841                 cprm->written += n;
842                 cprm->pos += n;
843                 nr -= n;
844         }
845         return 1;
846 }
847 EXPORT_SYMBOL(dump_emit);
848 
849 int dump_skip(struct coredump_params *cprm, size_t nr)
850 {
851         static char zeroes[PAGE_SIZE];
852         struct file *file = cprm->file;
853         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
854                 if (dump_interrupted() ||
855                     file->f_op->llseek(file, nr, SEEK_CUR) < 0)
856                         return 0;
857                 cprm->pos += nr;
858                 return 1;
859         } else {
860                 while (nr > PAGE_SIZE) {
861                         if (!dump_emit(cprm, zeroes, PAGE_SIZE))
862                                 return 0;
863                         nr -= PAGE_SIZE;
864                 }
865                 return dump_emit(cprm, zeroes, nr);
866         }
867 }
868 EXPORT_SYMBOL(dump_skip);
869 
870 int dump_align(struct coredump_params *cprm, int align)
871 {
872         unsigned mod = cprm->pos & (align - 1);
873         if (align & (align - 1))
874                 return 0;
875         return mod ? dump_skip(cprm, align - mod) : 1;
876 }
877 EXPORT_SYMBOL(dump_align);
878 
879 /*
880  * Ensures that file size is big enough to contain the current file
881  * postion. This prevents gdb from complaining about a truncated file
882  * if the last "write" to the file was dump_skip.
883  */
884 void dump_truncate(struct coredump_params *cprm)
885 {
886         struct file *file = cprm->file;
887         loff_t offset;
888 
889         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
890                 offset = file->f_op->llseek(file, 0, SEEK_CUR);
891                 if (i_size_read(file->f_mapping->host) < offset)
892                         do_truncate(file->f_path.dentry, offset, 0, file);
893         }
894 }
895 EXPORT_SYMBOL(dump_truncate);
896 

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