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TOMOYO Linux Cross Reference
Linux/fs/coredump.c

Version: ~ [ linux-5.2-rc1 ] ~ [ linux-5.1.2 ] ~ [ linux-5.0.16 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.43 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.119 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.176 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.179 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.139 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.67 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ 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/string.h>
 11 #include <linux/init.h>
 12 #include <linux/pagemap.h>
 13 #include <linux/perf_event.h>
 14 #include <linux/highmem.h>
 15 #include <linux/spinlock.h>
 16 #include <linux/key.h>
 17 #include <linux/personality.h>
 18 #include <linux/binfmts.h>
 19 #include <linux/coredump.h>
 20 #include <linux/sched/coredump.h>
 21 #include <linux/sched/signal.h>
 22 #include <linux/sched/task_stack.h>
 23 #include <linux/utsname.h>
 24 #include <linux/pid_namespace.h>
 25 #include <linux/module.h>
 26 #include <linux/namei.h>
 27 #include <linux/mount.h>
 28 #include <linux/security.h>
 29 #include <linux/syscalls.h>
 30 #include <linux/tsacct_kern.h>
 31 #include <linux/cn_proc.h>
 32 #include <linux/audit.h>
 33 #include <linux/tracehook.h>
 34 #include <linux/kmod.h>
 35 #include <linux/fsnotify.h>
 36 #include <linux/fs_struct.h>
 37 #include <linux/pipe_fs_i.h>
 38 #include <linux/oom.h>
 39 #include <linux/compat.h>
 40 #include <linux/fs.h>
 41 #include <linux/path.h>
 42 #include <linux/timekeeping.h>
 43 
 44 #include <linux/uaccess.h>
 45 #include <asm/mmu_context.h>
 46 #include <asm/tlb.h>
 47 #include <asm/exec.h>
 48 
 49 #include <trace/events/task.h>
 50 #include "internal.h"
 51 
 52 #include <trace/events/sched.h>
 53 
 54 int core_uses_pid;
 55 unsigned int core_pipe_limit;
 56 char core_pattern[CORENAME_MAX_SIZE] = "core";
 57 static int core_name_size = CORENAME_MAX_SIZE;
 58 
 59 struct core_name {
 60         char *corename;
 61         int used, size;
 62 };
 63 
 64 /* The maximal length of core_pattern is also specified in sysctl.c */
 65 
 66 static int expand_corename(struct core_name *cn, int size)
 67 {
 68         char *corename = krealloc(cn->corename, size, GFP_KERNEL);
 69 
 70         if (!corename)
 71                 return -ENOMEM;
 72 
 73         if (size > core_name_size) /* racy but harmless */
 74                 core_name_size = size;
 75 
 76         cn->size = ksize(corename);
 77         cn->corename = corename;
 78         return 0;
 79 }
 80 
 81 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
 82                                      va_list arg)
 83 {
 84         int free, need;
 85         va_list arg_copy;
 86 
 87 again:
 88         free = cn->size - cn->used;
 89 
 90         va_copy(arg_copy, arg);
 91         need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
 92         va_end(arg_copy);
 93 
 94         if (need < free) {
 95                 cn->used += need;
 96                 return 0;
 97         }
 98 
 99         if (!expand_corename(cn, cn->size + need - free + 1))
100                 goto again;
101 
102         return -ENOMEM;
103 }
104 
105 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
106 {
107         va_list arg;
108         int ret;
109 
110         va_start(arg, fmt);
111         ret = cn_vprintf(cn, fmt, arg);
112         va_end(arg);
113 
114         return ret;
115 }
116 
117 static __printf(2, 3)
118 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
119 {
120         int cur = cn->used;
121         va_list arg;
122         int ret;
123 
124         va_start(arg, fmt);
125         ret = cn_vprintf(cn, fmt, arg);
126         va_end(arg);
127 
128         if (ret == 0) {
129                 /*
130                  * Ensure that this coredump name component can't cause the
131                  * resulting corefile path to consist of a ".." or ".".
132                  */
133                 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
134                                 (cn->used - cur == 2 && cn->corename[cur] == '.'
135                                 && cn->corename[cur+1] == '.'))
136                         cn->corename[cur] = '!';
137 
138                 /*
139                  * Empty names are fishy and could be used to create a "//" in a
140                  * corefile name, causing the coredump to happen one directory
141                  * level too high. Enforce that all components of the core
142                  * pattern are at least one character long.
143                  */
144                 if (cn->used == cur)
145                         ret = cn_printf(cn, "!");
146         }
147 
148         for (; cur < cn->used; ++cur) {
149                 if (cn->corename[cur] == '/')
150                         cn->corename[cur] = '!';
151         }
152         return ret;
153 }
154 
155 static int cn_print_exe_file(struct core_name *cn)
156 {
157         struct file *exe_file;
158         char *pathbuf, *path;
159         int ret;
160 
161         exe_file = get_mm_exe_file(current->mm);
162         if (!exe_file)
163                 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
164 
165         pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
166         if (!pathbuf) {
167                 ret = -ENOMEM;
168                 goto put_exe_file;
169         }
170 
171         path = file_path(exe_file, pathbuf, PATH_MAX);
172         if (IS_ERR(path)) {
173                 ret = PTR_ERR(path);
174                 goto free_buf;
175         }
176 
177         ret = cn_esc_printf(cn, "%s", path);
178 
179 free_buf:
180         kfree(pathbuf);
181 put_exe_file:
182         fput(exe_file);
183         return ret;
184 }
185 
186 /* format_corename will inspect the pattern parameter, and output a
187  * name into corename, which must have space for at least
188  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
189  */
190 static int format_corename(struct core_name *cn, struct coredump_params *cprm)
191 {
192         const struct cred *cred = current_cred();
193         const char *pat_ptr = core_pattern;
194         int ispipe = (*pat_ptr == '|');
195         int pid_in_pattern = 0;
196         int err = 0;
197 
198         cn->used = 0;
199         cn->corename = NULL;
200         if (expand_corename(cn, core_name_size))
201                 return -ENOMEM;
202         cn->corename[0] = '\0';
203 
204         if (ispipe)
205                 ++pat_ptr;
206 
207         /* Repeat as long as we have more pattern to process and more output
208            space */
209         while (*pat_ptr) {
210                 if (*pat_ptr != '%') {
211                         err = cn_printf(cn, "%c", *pat_ptr++);
212                 } else {
213                         switch (*++pat_ptr) {
214                         /* single % at the end, drop that */
215                         case 0:
216                                 goto out;
217                         /* Double percent, output one percent */
218                         case '%':
219                                 err = cn_printf(cn, "%c", '%');
220                                 break;
221                         /* pid */
222                         case 'p':
223                                 pid_in_pattern = 1;
224                                 err = cn_printf(cn, "%d",
225                                               task_tgid_vnr(current));
226                                 break;
227                         /* global pid */
228                         case 'P':
229                                 err = cn_printf(cn, "%d",
230                                               task_tgid_nr(current));
231                                 break;
232                         case 'i':
233                                 err = cn_printf(cn, "%d",
234                                               task_pid_vnr(current));
235                                 break;
236                         case 'I':
237                                 err = cn_printf(cn, "%d",
238                                               task_pid_nr(current));
239                                 break;
240                         /* uid */
241                         case 'u':
242                                 err = cn_printf(cn, "%u",
243                                                 from_kuid(&init_user_ns,
244                                                           cred->uid));
245                                 break;
246                         /* gid */
247                         case 'g':
248                                 err = cn_printf(cn, "%u",
249                                                 from_kgid(&init_user_ns,
250                                                           cred->gid));
251                                 break;
252                         case 'd':
253                                 err = cn_printf(cn, "%d",
254                                         __get_dumpable(cprm->mm_flags));
255                                 break;
256                         /* signal that caused the coredump */
257                         case 's':
258                                 err = cn_printf(cn, "%d",
259                                                 cprm->siginfo->si_signo);
260                                 break;
261                         /* UNIX time of coredump */
262                         case 't': {
263                                 time64_t time;
264 
265                                 time = ktime_get_real_seconds();
266                                 err = cn_printf(cn, "%lld", time);
267                                 break;
268                         }
269                         /* hostname */
270                         case 'h':
271                                 down_read(&uts_sem);
272                                 err = cn_esc_printf(cn, "%s",
273                                               utsname()->nodename);
274                                 up_read(&uts_sem);
275                                 break;
276                         /* executable */
277                         case 'e':
278                                 err = cn_esc_printf(cn, "%s", current->comm);
279                                 break;
280                         case 'E':
281                                 err = cn_print_exe_file(cn);
282                                 break;
283                         /* core limit size */
284                         case 'c':
285                                 err = cn_printf(cn, "%lu",
286                                               rlimit(RLIMIT_CORE));
287                                 break;
288                         default:
289                                 break;
290                         }
291                         ++pat_ptr;
292                 }
293 
294                 if (err)
295                         return err;
296         }
297 
298 out:
299         /* Backward compatibility with core_uses_pid:
300          *
301          * If core_pattern does not include a %p (as is the default)
302          * and core_uses_pid is set, then .%pid will be appended to
303          * the filename. Do not do this for piped commands. */
304         if (!ispipe && !pid_in_pattern && core_uses_pid) {
305                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
306                 if (err)
307                         return err;
308         }
309         return ispipe;
310 }
311 
312 static int zap_process(struct task_struct *start, int exit_code, int flags)
313 {
314         struct task_struct *t;
315         int nr = 0;
316 
317         /* ignore all signals except SIGKILL, see prepare_signal() */
318         start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
319         start->signal->group_exit_code = exit_code;
320         start->signal->group_stop_count = 0;
321 
322         for_each_thread(start, t) {
323                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
324                 if (t != current && t->mm) {
325                         sigaddset(&t->pending.signal, SIGKILL);
326                         signal_wake_up(t, 1);
327                         nr++;
328                 }
329         }
330 
331         return nr;
332 }
333 
334 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
335                         struct core_state *core_state, int exit_code)
336 {
337         struct task_struct *g, *p;
338         unsigned long flags;
339         int nr = -EAGAIN;
340 
341         spin_lock_irq(&tsk->sighand->siglock);
342         if (!signal_group_exit(tsk->signal)) {
343                 mm->core_state = core_state;
344                 tsk->signal->group_exit_task = tsk;
345                 nr = zap_process(tsk, exit_code, 0);
346                 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
347         }
348         spin_unlock_irq(&tsk->sighand->siglock);
349         if (unlikely(nr < 0))
350                 return nr;
351 
352         tsk->flags |= PF_DUMPCORE;
353         if (atomic_read(&mm->mm_users) == nr + 1)
354                 goto done;
355         /*
356          * We should find and kill all tasks which use this mm, and we should
357          * count them correctly into ->nr_threads. We don't take tasklist
358          * lock, but this is safe wrt:
359          *
360          * fork:
361          *      None of sub-threads can fork after zap_process(leader). All
362          *      processes which were created before this point should be
363          *      visible to zap_threads() because copy_process() adds the new
364          *      process to the tail of init_task.tasks list, and lock/unlock
365          *      of ->siglock provides a memory barrier.
366          *
367          * do_exit:
368          *      The caller holds mm->mmap_sem. This means that the task which
369          *      uses this mm can't pass exit_mm(), so it can't exit or clear
370          *      its ->mm.
371          *
372          * de_thread:
373          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
374          *      we must see either old or new leader, this does not matter.
375          *      However, it can change p->sighand, so lock_task_sighand(p)
376          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
377          *      it can't fail.
378          *
379          *      Note also that "g" can be the old leader with ->mm == NULL
380          *      and already unhashed and thus removed from ->thread_group.
381          *      This is OK, __unhash_process()->list_del_rcu() does not
382          *      clear the ->next pointer, we will find the new leader via
383          *      next_thread().
384          */
385         rcu_read_lock();
386         for_each_process(g) {
387                 if (g == tsk->group_leader)
388                         continue;
389                 if (g->flags & PF_KTHREAD)
390                         continue;
391 
392                 for_each_thread(g, p) {
393                         if (unlikely(!p->mm))
394                                 continue;
395                         if (unlikely(p->mm == mm)) {
396                                 lock_task_sighand(p, &flags);
397                                 nr += zap_process(p, exit_code,
398                                                         SIGNAL_GROUP_EXIT);
399                                 unlock_task_sighand(p, &flags);
400                         }
401                         break;
402                 }
403         }
404         rcu_read_unlock();
405 done:
406         atomic_set(&core_state->nr_threads, nr);
407         return nr;
408 }
409 
410 static int coredump_wait(int exit_code, struct core_state *core_state)
411 {
412         struct task_struct *tsk = current;
413         struct mm_struct *mm = tsk->mm;
414         int core_waiters = -EBUSY;
415 
416         init_completion(&core_state->startup);
417         core_state->dumper.task = tsk;
418         core_state->dumper.next = NULL;
419 
420         if (down_write_killable(&mm->mmap_sem))
421                 return -EINTR;
422 
423         if (!mm->core_state)
424                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
425         up_write(&mm->mmap_sem);
426 
427         if (core_waiters > 0) {
428                 struct core_thread *ptr;
429 
430                 freezer_do_not_count();
431                 wait_for_completion(&core_state->startup);
432                 freezer_count();
433                 /*
434                  * Wait for all the threads to become inactive, so that
435                  * all the thread context (extended register state, like
436                  * fpu etc) gets copied to the memory.
437                  */
438                 ptr = core_state->dumper.next;
439                 while (ptr != NULL) {
440                         wait_task_inactive(ptr->task, 0);
441                         ptr = ptr->next;
442                 }
443         }
444 
445         return core_waiters;
446 }
447 
448 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
449 {
450         struct core_thread *curr, *next;
451         struct task_struct *task;
452 
453         spin_lock_irq(&current->sighand->siglock);
454         if (core_dumped && !__fatal_signal_pending(current))
455                 current->signal->group_exit_code |= 0x80;
456         current->signal->group_exit_task = NULL;
457         current->signal->flags = SIGNAL_GROUP_EXIT;
458         spin_unlock_irq(&current->sighand->siglock);
459 
460         next = mm->core_state->dumper.next;
461         while ((curr = next) != NULL) {
462                 next = curr->next;
463                 task = curr->task;
464                 /*
465                  * see exit_mm(), curr->task must not see
466                  * ->task == NULL before we read ->next.
467                  */
468                 smp_mb();
469                 curr->task = NULL;
470                 wake_up_process(task);
471         }
472 
473         mm->core_state = NULL;
474 }
475 
476 static bool dump_interrupted(void)
477 {
478         /*
479          * SIGKILL or freezing() interrupt the coredumping. Perhaps we
480          * can do try_to_freeze() and check __fatal_signal_pending(),
481          * but then we need to teach dump_write() to restart and clear
482          * TIF_SIGPENDING.
483          */
484         return signal_pending(current);
485 }
486 
487 static void wait_for_dump_helpers(struct file *file)
488 {
489         struct pipe_inode_info *pipe = file->private_data;
490 
491         pipe_lock(pipe);
492         pipe->readers++;
493         pipe->writers--;
494         wake_up_interruptible_sync(&pipe->wait);
495         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
496         pipe_unlock(pipe);
497 
498         /*
499          * We actually want wait_event_freezable() but then we need
500          * to clear TIF_SIGPENDING and improve dump_interrupted().
501          */
502         wait_event_interruptible(pipe->wait, pipe->readers == 1);
503 
504         pipe_lock(pipe);
505         pipe->readers--;
506         pipe->writers++;
507         pipe_unlock(pipe);
508 }
509 
510 /*
511  * umh_pipe_setup
512  * helper function to customize the process used
513  * to collect the core in userspace.  Specifically
514  * it sets up a pipe and installs it as fd 0 (stdin)
515  * for the process.  Returns 0 on success, or
516  * PTR_ERR on failure.
517  * Note that it also sets the core limit to 1.  This
518  * is a special value that we use to trap recursive
519  * core dumps
520  */
521 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
522 {
523         struct file *files[2];
524         struct coredump_params *cp = (struct coredump_params *)info->data;
525         int err = create_pipe_files(files, 0);
526         if (err)
527                 return err;
528 
529         cp->file = files[1];
530 
531         err = replace_fd(0, files[0], 0);
532         fput(files[0]);
533         /* and disallow core files too */
534         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
535 
536         return err;
537 }
538 
539 void do_coredump(const siginfo_t *siginfo)
540 {
541         struct core_state core_state;
542         struct core_name cn;
543         struct mm_struct *mm = current->mm;
544         struct linux_binfmt * binfmt;
545         const struct cred *old_cred;
546         struct cred *cred;
547         int retval = 0;
548         int ispipe;
549         struct files_struct *displaced;
550         /* require nonrelative corefile path and be extra careful */
551         bool need_suid_safe = false;
552         bool core_dumped = false;
553         static atomic_t core_dump_count = ATOMIC_INIT(0);
554         struct coredump_params cprm = {
555                 .siginfo = siginfo,
556                 .regs = signal_pt_regs(),
557                 .limit = rlimit(RLIMIT_CORE),
558                 /*
559                  * We must use the same mm->flags while dumping core to avoid
560                  * inconsistency of bit flags, since this flag is not protected
561                  * by any locks.
562                  */
563                 .mm_flags = mm->flags,
564         };
565 
566         audit_core_dumps(siginfo->si_signo);
567 
568         binfmt = mm->binfmt;
569         if (!binfmt || !binfmt->core_dump)
570                 goto fail;
571         if (!__get_dumpable(cprm.mm_flags))
572                 goto fail;
573 
574         cred = prepare_creds();
575         if (!cred)
576                 goto fail;
577         /*
578          * We cannot trust fsuid as being the "true" uid of the process
579          * nor do we know its entire history. We only know it was tainted
580          * so we dump it as root in mode 2, and only into a controlled
581          * environment (pipe handler or fully qualified path).
582          */
583         if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
584                 /* Setuid core dump mode */
585                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
586                 need_suid_safe = true;
587         }
588 
589         retval = coredump_wait(siginfo->si_signo, &core_state);
590         if (retval < 0)
591                 goto fail_creds;
592 
593         old_cred = override_creds(cred);
594 
595         ispipe = format_corename(&cn, &cprm);
596 
597         if (ispipe) {
598                 int dump_count;
599                 char **helper_argv;
600                 struct subprocess_info *sub_info;
601 
602                 if (ispipe < 0) {
603                         printk(KERN_WARNING "format_corename failed\n");
604                         printk(KERN_WARNING "Aborting core\n");
605                         goto fail_unlock;
606                 }
607 
608                 if (cprm.limit == 1) {
609                         /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
610                          *
611                          * Normally core limits are irrelevant to pipes, since
612                          * we're not writing to the file system, but we use
613                          * cprm.limit of 1 here as a special value, this is a
614                          * consistent way to catch recursive crashes.
615                          * We can still crash if the core_pattern binary sets
616                          * RLIM_CORE = !1, but it runs as root, and can do
617                          * lots of stupid things.
618                          *
619                          * Note that we use task_tgid_vnr here to grab the pid
620                          * of the process group leader.  That way we get the
621                          * right pid if a thread in a multi-threaded
622                          * core_pattern process dies.
623                          */
624                         printk(KERN_WARNING
625                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
626                                 task_tgid_vnr(current), current->comm);
627                         printk(KERN_WARNING "Aborting core\n");
628                         goto fail_unlock;
629                 }
630                 cprm.limit = RLIM_INFINITY;
631 
632                 dump_count = atomic_inc_return(&core_dump_count);
633                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
634                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
635                                task_tgid_vnr(current), current->comm);
636                         printk(KERN_WARNING "Skipping core dump\n");
637                         goto fail_dropcount;
638                 }
639 
640                 helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL);
641                 if (!helper_argv) {
642                         printk(KERN_WARNING "%s failed to allocate memory\n",
643                                __func__);
644                         goto fail_dropcount;
645                 }
646 
647                 retval = -ENOMEM;
648                 sub_info = call_usermodehelper_setup(helper_argv[0],
649                                                 helper_argv, NULL, GFP_KERNEL,
650                                                 umh_pipe_setup, NULL, &cprm);
651                 if (sub_info)
652                         retval = call_usermodehelper_exec(sub_info,
653                                                           UMH_WAIT_EXEC);
654 
655                 argv_free(helper_argv);
656                 if (retval) {
657                         printk(KERN_INFO "Core dump to |%s pipe failed\n",
658                                cn.corename);
659                         goto close_fail;
660                 }
661         } else {
662                 struct inode *inode;
663                 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
664                                  O_LARGEFILE | O_EXCL;
665 
666                 if (cprm.limit < binfmt->min_coredump)
667                         goto fail_unlock;
668 
669                 if (need_suid_safe && cn.corename[0] != '/') {
670                         printk(KERN_WARNING "Pid %d(%s) can only dump core "\
671                                 "to fully qualified path!\n",
672                                 task_tgid_vnr(current), current->comm);
673                         printk(KERN_WARNING "Skipping core dump\n");
674                         goto fail_unlock;
675                 }
676 
677                 /*
678                  * Unlink the file if it exists unless this is a SUID
679                  * binary - in that case, we're running around with root
680                  * privs and don't want to unlink another user's coredump.
681                  */
682                 if (!need_suid_safe) {
683                         /*
684                          * If it doesn't exist, that's fine. If there's some
685                          * other problem, we'll catch it at the filp_open().
686                          */
687                         do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
688                 }
689 
690                 /*
691                  * There is a race between unlinking and creating the
692                  * file, but if that causes an EEXIST here, that's
693                  * fine - another process raced with us while creating
694                  * the corefile, and the other process won. To userspace,
695                  * what matters is that at least one of the two processes
696                  * writes its coredump successfully, not which one.
697                  */
698                 if (need_suid_safe) {
699                         /*
700                          * Using user namespaces, normal user tasks can change
701                          * their current->fs->root to point to arbitrary
702                          * directories. Since the intention of the "only dump
703                          * with a fully qualified path" rule is to control where
704                          * coredumps may be placed using root privileges,
705                          * current->fs->root must not be used. Instead, use the
706                          * root directory of init_task.
707                          */
708                         struct path root;
709 
710                         task_lock(&init_task);
711                         get_fs_root(init_task.fs, &root);
712                         task_unlock(&init_task);
713                         cprm.file = file_open_root(root.dentry, root.mnt,
714                                 cn.corename, open_flags, 0600);
715                         path_put(&root);
716                 } else {
717                         cprm.file = filp_open(cn.corename, open_flags, 0600);
718                 }
719                 if (IS_ERR(cprm.file))
720                         goto fail_unlock;
721 
722                 inode = file_inode(cprm.file);
723                 if (inode->i_nlink > 1)
724                         goto close_fail;
725                 if (d_unhashed(cprm.file->f_path.dentry))
726                         goto close_fail;
727                 /*
728                  * AK: actually i see no reason to not allow this for named
729                  * pipes etc, but keep the previous behaviour for now.
730                  */
731                 if (!S_ISREG(inode->i_mode))
732                         goto close_fail;
733                 /*
734                  * Don't dump core if the filesystem changed owner or mode
735                  * of the file during file creation. This is an issue when
736                  * a process dumps core while its cwd is e.g. on a vfat
737                  * filesystem.
738                  */
739                 if (!uid_eq(inode->i_uid, current_fsuid()))
740                         goto close_fail;
741                 if ((inode->i_mode & 0677) != 0600)
742                         goto close_fail;
743                 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
744                         goto close_fail;
745                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
746                         goto close_fail;
747         }
748 
749         /* get us an unshared descriptor table; almost always a no-op */
750         retval = unshare_files(&displaced);
751         if (retval)
752                 goto close_fail;
753         if (displaced)
754                 put_files_struct(displaced);
755         if (!dump_interrupted()) {
756                 file_start_write(cprm.file);
757                 core_dumped = binfmt->core_dump(&cprm);
758                 file_end_write(cprm.file);
759         }
760         if (ispipe && core_pipe_limit)
761                 wait_for_dump_helpers(cprm.file);
762 close_fail:
763         if (cprm.file)
764                 filp_close(cprm.file, NULL);
765 fail_dropcount:
766         if (ispipe)
767                 atomic_dec(&core_dump_count);
768 fail_unlock:
769         kfree(cn.corename);
770         coredump_finish(mm, core_dumped);
771         revert_creds(old_cred);
772 fail_creds:
773         put_cred(cred);
774 fail:
775         return;
776 }
777 
778 /*
779  * Core dumping helper functions.  These are the only things you should
780  * do on a core-file: use only these functions to write out all the
781  * necessary info.
782  */
783 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
784 {
785         struct file *file = cprm->file;
786         loff_t pos = file->f_pos;
787         ssize_t n;
788         if (cprm->written + nr > cprm->limit)
789                 return 0;
790         while (nr) {
791                 if (dump_interrupted())
792                         return 0;
793                 n = __kernel_write(file, addr, nr, &pos);
794                 if (n <= 0)
795                         return 0;
796                 file->f_pos = pos;
797                 cprm->written += n;
798                 cprm->pos += n;
799                 nr -= n;
800         }
801         return 1;
802 }
803 EXPORT_SYMBOL(dump_emit);
804 
805 int dump_skip(struct coredump_params *cprm, size_t nr)
806 {
807         static char zeroes[PAGE_SIZE];
808         struct file *file = cprm->file;
809         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
810                 if (dump_interrupted() ||
811                     file->f_op->llseek(file, nr, SEEK_CUR) < 0)
812                         return 0;
813                 cprm->pos += nr;
814                 return 1;
815         } else {
816                 while (nr > PAGE_SIZE) {
817                         if (!dump_emit(cprm, zeroes, PAGE_SIZE))
818                                 return 0;
819                         nr -= PAGE_SIZE;
820                 }
821                 return dump_emit(cprm, zeroes, nr);
822         }
823 }
824 EXPORT_SYMBOL(dump_skip);
825 
826 int dump_align(struct coredump_params *cprm, int align)
827 {
828         unsigned mod = cprm->pos & (align - 1);
829         if (align & (align - 1))
830                 return 0;
831         return mod ? dump_skip(cprm, align - mod) : 1;
832 }
833 EXPORT_SYMBOL(dump_align);
834 
835 /*
836  * Ensures that file size is big enough to contain the current file
837  * postion. This prevents gdb from complaining about a truncated file
838  * if the last "write" to the file was dump_skip.
839  */
840 void dump_truncate(struct coredump_params *cprm)
841 {
842         struct file *file = cprm->file;
843         loff_t offset;
844 
845         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
846                 offset = file->f_op->llseek(file, 0, SEEK_CUR);
847                 if (i_size_read(file->f_mapping->host) < offset)
848                         do_truncate(file->f_path.dentry, offset, 0, file);
849         }
850 }
851 EXPORT_SYMBOL(dump_truncate);
852 

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