~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/fs/coredump.c

Version: ~ [ linux-5.15-rc5 ] ~ [ linux-5.14.11 ] ~ [ linux-5.13.19 ] ~ [ linux-5.12.19 ] ~ [ linux-5.11.22 ] ~ [ linux-5.10.72 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.152 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.210 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.250 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.286 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.288 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

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

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp