Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/fs/coredump.c

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

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