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TOMOYO Linux Cross Reference
Linux/fs/coredump.c

Version: ~ [ linux-5.13-rc5 ] ~ [ linux-5.12.9 ] ~ [ linux-5.11.22 ] ~ [ linux-5.10.42 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.124 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.193 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.235 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.271 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.271 ] ~ [ 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 ] ~
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  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         }
215 
216         /* Repeat as long as we have more pattern to process and more output
217            space */
218         while (*pat_ptr) {
219                 /*
220                  * Split on spaces before doing template expansion so that
221                  * %e and %E don't get split if they have spaces in them
222                  */
223                 if (ispipe) {
224                         if (isspace(*pat_ptr)) {
225                                 was_space = true;
226                                 pat_ptr++;
227                                 continue;
228                         } else if (was_space) {
229                                 was_space = false;
230                                 err = cn_printf(cn, "%c", '\0');
231                                 if (err)
232                                         return err;
233                                 (*argv)[(*argc)++] = cn->used;
234                         }
235                 }
236                 if (*pat_ptr != '%') {
237                         err = cn_printf(cn, "%c", *pat_ptr++);
238                 } else {
239                         switch (*++pat_ptr) {
240                         /* single % at the end, drop that */
241                         case 0:
242                                 goto out;
243                         /* Double percent, output one percent */
244                         case '%':
245                                 err = cn_printf(cn, "%c", '%');
246                                 break;
247                         /* pid */
248                         case 'p':
249                                 pid_in_pattern = 1;
250                                 err = cn_printf(cn, "%d",
251                                               task_tgid_vnr(current));
252                                 break;
253                         /* global pid */
254                         case 'P':
255                                 err = cn_printf(cn, "%d",
256                                               task_tgid_nr(current));
257                                 break;
258                         case 'i':
259                                 err = cn_printf(cn, "%d",
260                                               task_pid_vnr(current));
261                                 break;
262                         case 'I':
263                                 err = cn_printf(cn, "%d",
264                                               task_pid_nr(current));
265                                 break;
266                         /* uid */
267                         case 'u':
268                                 err = cn_printf(cn, "%u",
269                                                 from_kuid(&init_user_ns,
270                                                           cred->uid));
271                                 break;
272                         /* gid */
273                         case 'g':
274                                 err = cn_printf(cn, "%u",
275                                                 from_kgid(&init_user_ns,
276                                                           cred->gid));
277                                 break;
278                         case 'd':
279                                 err = cn_printf(cn, "%d",
280                                         __get_dumpable(cprm->mm_flags));
281                                 break;
282                         /* signal that caused the coredump */
283                         case 's':
284                                 err = cn_printf(cn, "%d",
285                                                 cprm->siginfo->si_signo);
286                                 break;
287                         /* UNIX time of coredump */
288                         case 't': {
289                                 time64_t time;
290 
291                                 time = ktime_get_real_seconds();
292                                 err = cn_printf(cn, "%lld", time);
293                                 break;
294                         }
295                         /* hostname */
296                         case 'h':
297                                 down_read(&uts_sem);
298                                 err = cn_esc_printf(cn, "%s",
299                                               utsname()->nodename);
300                                 up_read(&uts_sem);
301                                 break;
302                         /* executable */
303                         case 'e':
304                                 err = cn_esc_printf(cn, "%s", current->comm);
305                                 break;
306                         case 'E':
307                                 err = cn_print_exe_file(cn);
308                                 break;
309                         /* core limit size */
310                         case 'c':
311                                 err = cn_printf(cn, "%lu",
312                                               rlimit(RLIMIT_CORE));
313                                 break;
314                         default:
315                                 break;
316                         }
317                         ++pat_ptr;
318                 }
319 
320                 if (err)
321                         return err;
322         }
323 
324 out:
325         /* Backward compatibility with core_uses_pid:
326          *
327          * If core_pattern does not include a %p (as is the default)
328          * and core_uses_pid is set, then .%pid will be appended to
329          * the filename. Do not do this for piped commands. */
330         if (!ispipe && !pid_in_pattern && core_uses_pid) {
331                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
332                 if (err)
333                         return err;
334         }
335         return ispipe;
336 }
337 
338 static int zap_process(struct task_struct *start, int exit_code, int flags)
339 {
340         struct task_struct *t;
341         int nr = 0;
342 
343         /* ignore all signals except SIGKILL, see prepare_signal() */
344         start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
345         start->signal->group_exit_code = exit_code;
346         start->signal->group_stop_count = 0;
347 
348         for_each_thread(start, t) {
349                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
350                 if (t != current && t->mm) {
351                         sigaddset(&t->pending.signal, SIGKILL);
352                         signal_wake_up(t, 1);
353                         nr++;
354                 }
355         }
356 
357         return nr;
358 }
359 
360 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
361                         struct core_state *core_state, int exit_code)
362 {
363         struct task_struct *g, *p;
364         unsigned long flags;
365         int nr = -EAGAIN;
366 
367         spin_lock_irq(&tsk->sighand->siglock);
368         if (!signal_group_exit(tsk->signal)) {
369                 mm->core_state = core_state;
370                 tsk->signal->group_exit_task = tsk;
371                 nr = zap_process(tsk, exit_code, 0);
372                 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
373         }
374         spin_unlock_irq(&tsk->sighand->siglock);
375         if (unlikely(nr < 0))
376                 return nr;
377 
378         tsk->flags |= PF_DUMPCORE;
379         if (atomic_read(&mm->mm_users) == nr + 1)
380                 goto done;
381         /*
382          * We should find and kill all tasks which use this mm, and we should
383          * count them correctly into ->nr_threads. We don't take tasklist
384          * lock, but this is safe wrt:
385          *
386          * fork:
387          *      None of sub-threads can fork after zap_process(leader). All
388          *      processes which were created before this point should be
389          *      visible to zap_threads() because copy_process() adds the new
390          *      process to the tail of init_task.tasks list, and lock/unlock
391          *      of ->siglock provides a memory barrier.
392          *
393          * do_exit:
394          *      The caller holds mm->mmap_sem. This means that the task which
395          *      uses this mm can't pass exit_mm(), so it can't exit or clear
396          *      its ->mm.
397          *
398          * de_thread:
399          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
400          *      we must see either old or new leader, this does not matter.
401          *      However, it can change p->sighand, so lock_task_sighand(p)
402          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
403          *      it can't fail.
404          *
405          *      Note also that "g" can be the old leader with ->mm == NULL
406          *      and already unhashed and thus removed from ->thread_group.
407          *      This is OK, __unhash_process()->list_del_rcu() does not
408          *      clear the ->next pointer, we will find the new leader via
409          *      next_thread().
410          */
411         rcu_read_lock();
412         for_each_process(g) {
413                 if (g == tsk->group_leader)
414                         continue;
415                 if (g->flags & PF_KTHREAD)
416                         continue;
417 
418                 for_each_thread(g, p) {
419                         if (unlikely(!p->mm))
420                                 continue;
421                         if (unlikely(p->mm == mm)) {
422                                 lock_task_sighand(p, &flags);
423                                 nr += zap_process(p, exit_code,
424                                                         SIGNAL_GROUP_EXIT);
425                                 unlock_task_sighand(p, &flags);
426                         }
427                         break;
428                 }
429         }
430         rcu_read_unlock();
431 done:
432         atomic_set(&core_state->nr_threads, nr);
433         return nr;
434 }
435 
436 static int coredump_wait(int exit_code, struct core_state *core_state)
437 {
438         struct task_struct *tsk = current;
439         struct mm_struct *mm = tsk->mm;
440         int core_waiters = -EBUSY;
441 
442         init_completion(&core_state->startup);
443         core_state->dumper.task = tsk;
444         core_state->dumper.next = NULL;
445 
446         if (down_write_killable(&mm->mmap_sem))
447                 return -EINTR;
448 
449         if (!mm->core_state)
450                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
451         up_write(&mm->mmap_sem);
452 
453         if (core_waiters > 0) {
454                 struct core_thread *ptr;
455 
456                 freezer_do_not_count();
457                 wait_for_completion(&core_state->startup);
458                 freezer_count();
459                 /*
460                  * Wait for all the threads to become inactive, so that
461                  * all the thread context (extended register state, like
462                  * fpu etc) gets copied to the memory.
463                  */
464                 ptr = core_state->dumper.next;
465                 while (ptr != NULL) {
466                         wait_task_inactive(ptr->task, 0);
467                         ptr = ptr->next;
468                 }
469         }
470 
471         return core_waiters;
472 }
473 
474 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
475 {
476         struct core_thread *curr, *next;
477         struct task_struct *task;
478 
479         spin_lock_irq(&current->sighand->siglock);
480         if (core_dumped && !__fatal_signal_pending(current))
481                 current->signal->group_exit_code |= 0x80;
482         current->signal->group_exit_task = NULL;
483         current->signal->flags = SIGNAL_GROUP_EXIT;
484         spin_unlock_irq(&current->sighand->siglock);
485 
486         next = mm->core_state->dumper.next;
487         while ((curr = next) != NULL) {
488                 next = curr->next;
489                 task = curr->task;
490                 /*
491                  * see exit_mm(), curr->task must not see
492                  * ->task == NULL before we read ->next.
493                  */
494                 smp_mb();
495                 curr->task = NULL;
496                 wake_up_process(task);
497         }
498 
499         mm->core_state = NULL;
500 }
501 
502 static bool dump_interrupted(void)
503 {
504         /*
505          * SIGKILL or freezing() interrupt the coredumping. Perhaps we
506          * can do try_to_freeze() and check __fatal_signal_pending(),
507          * but then we need to teach dump_write() to restart and clear
508          * TIF_SIGPENDING.
509          */
510         return signal_pending(current);
511 }
512 
513 static void wait_for_dump_helpers(struct file *file)
514 {
515         struct pipe_inode_info *pipe = file->private_data;
516 
517         pipe_lock(pipe);
518         pipe->readers++;
519         pipe->writers--;
520         wake_up_interruptible_sync(&pipe->wait);
521         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
522         pipe_unlock(pipe);
523 
524         /*
525          * We actually want wait_event_freezable() but then we need
526          * to clear TIF_SIGPENDING and improve dump_interrupted().
527          */
528         wait_event_interruptible(pipe->wait, pipe->readers == 1);
529 
530         pipe_lock(pipe);
531         pipe->readers--;
532         pipe->writers++;
533         pipe_unlock(pipe);
534 }
535 
536 /*
537  * umh_pipe_setup
538  * helper function to customize the process used
539  * to collect the core in userspace.  Specifically
540  * it sets up a pipe and installs it as fd 0 (stdin)
541  * for the process.  Returns 0 on success, or
542  * PTR_ERR on failure.
543  * Note that it also sets the core limit to 1.  This
544  * is a special value that we use to trap recursive
545  * core dumps
546  */
547 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
548 {
549         struct file *files[2];
550         struct coredump_params *cp = (struct coredump_params *)info->data;
551         int err = create_pipe_files(files, 0);
552         if (err)
553                 return err;
554 
555         cp->file = files[1];
556 
557         err = replace_fd(0, files[0], 0);
558         fput(files[0]);
559         /* and disallow core files too */
560         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
561 
562         return err;
563 }
564 
565 void do_coredump(const kernel_siginfo_t *siginfo)
566 {
567         struct core_state core_state;
568         struct core_name cn;
569         struct mm_struct *mm = current->mm;
570         struct linux_binfmt * binfmt;
571         const struct cred *old_cred;
572         struct cred *cred;
573         int retval = 0;
574         int ispipe;
575         size_t *argv = NULL;
576         int argc = 0;
577         struct files_struct *displaced;
578         /* require nonrelative corefile path and be extra careful */
579         bool need_suid_safe = false;
580         bool core_dumped = false;
581         static atomic_t core_dump_count = ATOMIC_INIT(0);
582         struct coredump_params cprm = {
583                 .siginfo = siginfo,
584                 .regs = signal_pt_regs(),
585                 .limit = rlimit(RLIMIT_CORE),
586                 /*
587                  * We must use the same mm->flags while dumping core to avoid
588                  * inconsistency of bit flags, since this flag is not protected
589                  * by any locks.
590                  */
591                 .mm_flags = mm->flags,
592         };
593 
594         audit_core_dumps(siginfo->si_signo);
595 
596         binfmt = mm->binfmt;
597         if (!binfmt || !binfmt->core_dump)
598                 goto fail;
599         if (!__get_dumpable(cprm.mm_flags))
600                 goto fail;
601 
602         cred = prepare_creds();
603         if (!cred)
604                 goto fail;
605         /*
606          * We cannot trust fsuid as being the "true" uid of the process
607          * nor do we know its entire history. We only know it was tainted
608          * so we dump it as root in mode 2, and only into a controlled
609          * environment (pipe handler or fully qualified path).
610          */
611         if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
612                 /* Setuid core dump mode */
613                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
614                 need_suid_safe = true;
615         }
616 
617         retval = coredump_wait(siginfo->si_signo, &core_state);
618         if (retval < 0)
619                 goto fail_creds;
620 
621         old_cred = override_creds(cred);
622 
623         ispipe = format_corename(&cn, &cprm, &argv, &argc);
624 
625         if (ispipe) {
626                 int argi;
627                 int dump_count;
628                 char **helper_argv;
629                 struct subprocess_info *sub_info;
630 
631                 if (ispipe < 0) {
632                         printk(KERN_WARNING "format_corename failed\n");
633                         printk(KERN_WARNING "Aborting core\n");
634                         goto fail_unlock;
635                 }
636 
637                 if (cprm.limit == 1) {
638                         /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
639                          *
640                          * Normally core limits are irrelevant to pipes, since
641                          * we're not writing to the file system, but we use
642                          * cprm.limit of 1 here as a special value, this is a
643                          * consistent way to catch recursive crashes.
644                          * We can still crash if the core_pattern binary sets
645                          * RLIM_CORE = !1, but it runs as root, and can do
646                          * lots of stupid things.
647                          *
648                          * Note that we use task_tgid_vnr here to grab the pid
649                          * of the process group leader.  That way we get the
650                          * right pid if a thread in a multi-threaded
651                          * core_pattern process dies.
652                          */
653                         printk(KERN_WARNING
654                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
655                                 task_tgid_vnr(current), current->comm);
656                         printk(KERN_WARNING "Aborting core\n");
657                         goto fail_unlock;
658                 }
659                 cprm.limit = RLIM_INFINITY;
660 
661                 dump_count = atomic_inc_return(&core_dump_count);
662                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
663                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
664                                task_tgid_vnr(current), current->comm);
665                         printk(KERN_WARNING "Skipping core dump\n");
666                         goto fail_dropcount;
667                 }
668 
669                 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
670                                             GFP_KERNEL);
671                 if (!helper_argv) {
672                         printk(KERN_WARNING "%s failed to allocate memory\n",
673                                __func__);
674                         goto fail_dropcount;
675                 }
676                 for (argi = 0; argi < argc; argi++)
677                         helper_argv[argi] = cn.corename + argv[argi];
678                 helper_argv[argi] = NULL;
679 
680                 retval = -ENOMEM;
681                 sub_info = call_usermodehelper_setup(helper_argv[0],
682                                                 helper_argv, NULL, GFP_KERNEL,
683                                                 umh_pipe_setup, NULL, &cprm);
684                 if (sub_info)
685                         retval = call_usermodehelper_exec(sub_info,
686                                                           UMH_WAIT_EXEC);
687 
688                 kfree(helper_argv);
689                 if (retval) {
690                         printk(KERN_INFO "Core dump to |%s pipe failed\n",
691                                cn.corename);
692                         goto close_fail;
693                 }
694         } else {
695                 struct inode *inode;
696                 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
697                                  O_LARGEFILE | O_EXCL;
698 
699                 if (cprm.limit < binfmt->min_coredump)
700                         goto fail_unlock;
701 
702                 if (need_suid_safe && cn.corename[0] != '/') {
703                         printk(KERN_WARNING "Pid %d(%s) can only dump core "\
704                                 "to fully qualified path!\n",
705                                 task_tgid_vnr(current), current->comm);
706                         printk(KERN_WARNING "Skipping core dump\n");
707                         goto fail_unlock;
708                 }
709 
710                 /*
711                  * Unlink the file if it exists unless this is a SUID
712                  * binary - in that case, we're running around with root
713                  * privs and don't want to unlink another user's coredump.
714                  */
715                 if (!need_suid_safe) {
716                         /*
717                          * If it doesn't exist, that's fine. If there's some
718                          * other problem, we'll catch it at the filp_open().
719                          */
720                         do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
721                 }
722 
723                 /*
724                  * There is a race between unlinking and creating the
725                  * file, but if that causes an EEXIST here, that's
726                  * fine - another process raced with us while creating
727                  * the corefile, and the other process won. To userspace,
728                  * what matters is that at least one of the two processes
729                  * writes its coredump successfully, not which one.
730                  */
731                 if (need_suid_safe) {
732                         /*
733                          * Using user namespaces, normal user tasks can change
734                          * their current->fs->root to point to arbitrary
735                          * directories. Since the intention of the "only dump
736                          * with a fully qualified path" rule is to control where
737                          * coredumps may be placed using root privileges,
738                          * current->fs->root must not be used. Instead, use the
739                          * root directory of init_task.
740                          */
741                         struct path root;
742 
743                         task_lock(&init_task);
744                         get_fs_root(init_task.fs, &root);
745                         task_unlock(&init_task);
746                         cprm.file = file_open_root(root.dentry, root.mnt,
747                                 cn.corename, open_flags, 0600);
748                         path_put(&root);
749                 } else {
750                         cprm.file = filp_open(cn.corename, open_flags, 0600);
751                 }
752                 if (IS_ERR(cprm.file))
753                         goto fail_unlock;
754 
755                 inode = file_inode(cprm.file);
756                 if (inode->i_nlink > 1)
757                         goto close_fail;
758                 if (d_unhashed(cprm.file->f_path.dentry))
759                         goto close_fail;
760                 /*
761                  * AK: actually i see no reason to not allow this for named
762                  * pipes etc, but keep the previous behaviour for now.
763                  */
764                 if (!S_ISREG(inode->i_mode))
765                         goto close_fail;
766                 /*
767                  * Don't dump core if the filesystem changed owner or mode
768                  * of the file during file creation. This is an issue when
769                  * a process dumps core while its cwd is e.g. on a vfat
770                  * filesystem.
771                  */
772                 if (!uid_eq(inode->i_uid, current_fsuid()))
773                         goto close_fail;
774                 if ((inode->i_mode & 0677) != 0600)
775                         goto close_fail;
776                 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
777                         goto close_fail;
778                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
779                         goto close_fail;
780         }
781 
782         /* get us an unshared descriptor table; almost always a no-op */
783         retval = unshare_files(&displaced);
784         if (retval)
785                 goto close_fail;
786         if (displaced)
787                 put_files_struct(displaced);
788         if (!dump_interrupted()) {
789                 file_start_write(cprm.file);
790                 core_dumped = binfmt->core_dump(&cprm);
791                 file_end_write(cprm.file);
792         }
793         if (ispipe && core_pipe_limit)
794                 wait_for_dump_helpers(cprm.file);
795 close_fail:
796         if (cprm.file)
797                 filp_close(cprm.file, NULL);
798 fail_dropcount:
799         if (ispipe)
800                 atomic_dec(&core_dump_count);
801 fail_unlock:
802         kfree(argv);
803         kfree(cn.corename);
804         coredump_finish(mm, core_dumped);
805         revert_creds(old_cred);
806 fail_creds:
807         put_cred(cred);
808 fail:
809         return;
810 }
811 
812 /*
813  * Core dumping helper functions.  These are the only things you should
814  * do on a core-file: use only these functions to write out all the
815  * necessary info.
816  */
817 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
818 {
819         struct file *file = cprm->file;
820         loff_t pos = file->f_pos;
821         ssize_t n;
822         if (cprm->written + nr > cprm->limit)
823                 return 0;
824         while (nr) {
825                 if (dump_interrupted())
826                         return 0;
827                 n = __kernel_write(file, addr, nr, &pos);
828                 if (n <= 0)
829                         return 0;
830                 file->f_pos = pos;
831                 cprm->written += n;
832                 cprm->pos += n;
833                 nr -= n;
834         }
835         return 1;
836 }
837 EXPORT_SYMBOL(dump_emit);
838 
839 int dump_skip(struct coredump_params *cprm, size_t nr)
840 {
841         static char zeroes[PAGE_SIZE];
842         struct file *file = cprm->file;
843         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
844                 if (dump_interrupted() ||
845                     file->f_op->llseek(file, nr, SEEK_CUR) < 0)
846                         return 0;
847                 cprm->pos += nr;
848                 return 1;
849         } else {
850                 while (nr > PAGE_SIZE) {
851                         if (!dump_emit(cprm, zeroes, PAGE_SIZE))
852                                 return 0;
853                         nr -= PAGE_SIZE;
854                 }
855                 return dump_emit(cprm, zeroes, nr);
856         }
857 }
858 EXPORT_SYMBOL(dump_skip);
859 
860 int dump_align(struct coredump_params *cprm, int align)
861 {
862         unsigned mod = cprm->pos & (align - 1);
863         if (align & (align - 1))
864                 return 0;
865         return mod ? dump_skip(cprm, align - mod) : 1;
866 }
867 EXPORT_SYMBOL(dump_align);
868 
869 /*
870  * Ensures that file size is big enough to contain the current file
871  * postion. This prevents gdb from complaining about a truncated file
872  * if the last "write" to the file was dump_skip.
873  */
874 void dump_truncate(struct coredump_params *cprm)
875 {
876         struct file *file = cprm->file;
877         loff_t offset;
878 
879         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
880                 offset = file->f_op->llseek(file, 0, SEEK_CUR);
881                 if (i_size_read(file->f_mapping->host) < offset)
882                         do_truncate(file->f_path.dentry, offset, 0, file);
883         }
884 }
885 EXPORT_SYMBOL(dump_truncate);
886 

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