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1#include <linux/slab.h>
2#include <linux/file.h>
3#include <linux/fdtable.h>
4#include <linux/mm.h>
5#include <linux/stat.h>
6#include <linux/fcntl.h>
7#include <linux/swap.h>
8#include <linux/string.h>
9#include <linux/init.h>
10#include <linux/pagemap.h>
11#include <linux/perf_event.h>
12#include <linux/highmem.h>
13#include <linux/spinlock.h>
14#include <linux/key.h>
15#include <linux/personality.h>
16#include <linux/binfmts.h>
17#include <linux/coredump.h>
18#include <linux/utsname.h>
19#include <linux/pid_namespace.h>
20#include <linux/module.h>
21#include <linux/namei.h>
22#include <linux/mount.h>
23#include <linux/security.h>
24#include <linux/syscalls.h>
25#include <linux/tsacct_kern.h>
26#include <linux/cn_proc.h>
27#include <linux/audit.h>
28#include <linux/tracehook.h>
29#include <linux/kmod.h>
30#include <linux/fsnotify.h>
31#include <linux/fs_struct.h>
32#include <linux/pipe_fs_i.h>
33#include <linux/oom.h>
34#include <linux/compat.h>
35#include <linux/sched.h>
36#include <linux/fs.h>
37#include <linux/path.h>
38#include <linux/timekeeping.h>
39
40#include <asm/uaccess.h>
41#include <asm/mmu_context.h>
42#include <asm/tlb.h>
43#include <asm/exec.h>
44
45#include <trace/events/task.h>
46#include "internal.h"
47
48#include <trace/events/sched.h>
49
50int core_uses_pid;
51unsigned int core_pipe_limit;
52char core_pattern[CORENAME_MAX_SIZE] = "core";
53static int core_name_size = CORENAME_MAX_SIZE;
54
55struct core_name {
56 char *corename;
57 int used, size;
58};
59
60/* The maximal length of core_pattern is also specified in sysctl.c */
61
62static int expand_corename(struct core_name *cn, int size)
63{
64 char *corename = krealloc(cn->corename, size, GFP_KERNEL);
65
66 if (!corename)
67 return -ENOMEM;
68
69 if (size > core_name_size) /* racy but harmless */
70 core_name_size = size;
71
72 cn->size = ksize(corename);
73 cn->corename = corename;
74 return 0;
75}
76
77static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
78 va_list arg)
79{
80 int free, need;
81 va_list arg_copy;
82
83again:
84 free = cn->size - cn->used;
85
86 va_copy(arg_copy, arg);
87 need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
88 va_end(arg_copy);
89
90 if (need < free) {
91 cn->used += need;
92 return 0;
93 }
94
95 if (!expand_corename(cn, cn->size + need - free + 1))
96 goto again;
97
98 return -ENOMEM;
99}
100
101static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
102{
103 va_list arg;
104 int ret;
105
106 va_start(arg, fmt);
107 ret = cn_vprintf(cn, fmt, arg);
108 va_end(arg);
109
110 return ret;
111}
112
113static __printf(2, 3)
114int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
115{
116 int cur = cn->used;
117 va_list arg;
118 int ret;
119
120 va_start(arg, fmt);
121 ret = cn_vprintf(cn, fmt, arg);
122 va_end(arg);
123
124 if (ret == 0) {
125 /*
126 * Ensure that this coredump name component can't cause the
127 * resulting corefile path to consist of a ".." or ".".
128 */
129 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
130 (cn->used - cur == 2 && cn->corename[cur] == '.'
131 && cn->corename[cur+1] == '.'))
132 cn->corename[cur] = '!';
133
134 /*
135 * Empty names are fishy and could be used to create a "//" in a
136 * corefile name, causing the coredump to happen one directory
137 * level too high. Enforce that all components of the core
138 * pattern are at least one character long.
139 */
140 if (cn->used == cur)
141 ret = cn_printf(cn, "!");
142 }
143
144 for (; cur < cn->used; ++cur) {
145 if (cn->corename[cur] == '/')
146 cn->corename[cur] = '!';
147 }
148 return ret;
149}
150
151static int cn_print_exe_file(struct core_name *cn)
152{
153 struct file *exe_file;
154 char *pathbuf, *path;
155 int ret;
156
157 exe_file = get_mm_exe_file(current->mm);
158 if (!exe_file)
159 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
160
161 pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
162 if (!pathbuf) {
163 ret = -ENOMEM;
164 goto put_exe_file;
165 }
166
167 path = file_path(exe_file, pathbuf, PATH_MAX);
168 if (IS_ERR(path)) {
169 ret = PTR_ERR(path);
170 goto free_buf;
171 }
172
173 ret = cn_esc_printf(cn, "%s", path);
174
175free_buf:
176 kfree(pathbuf);
177put_exe_file:
178 fput(exe_file);
179 return ret;
180}
181
182/* format_corename will inspect the pattern parameter, and output a
183 * name into corename, which must have space for at least
184 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
185 */
186static int format_corename(struct core_name *cn, struct coredump_params *cprm)
187{
188 const struct cred *cred = current_cred();
189 const char *pat_ptr = core_pattern;
190 int ispipe = (*pat_ptr == '|');
191 int pid_in_pattern = 0;
192 int err = 0;
193
194 cn->used = 0;
195 cn->corename = NULL;
196 if (expand_corename(cn, core_name_size))
197 return -ENOMEM;
198 cn->corename[0] = '\0';
199
200 if (ispipe)
201 ++pat_ptr;
202
203 /* Repeat as long as we have more pattern to process and more output
204 space */
205 while (*pat_ptr) {
206 if (*pat_ptr != '%') {
207 err = cn_printf(cn, "%c", *pat_ptr++);
208 } else {
209 switch (*++pat_ptr) {
210 /* single % at the end, drop that */
211 case 0:
212 goto out;
213 /* Double percent, output one percent */
214 case '%':
215 err = cn_printf(cn, "%c", '%');
216 break;
217 /* pid */
218 case 'p':
219 pid_in_pattern = 1;
220 err = cn_printf(cn, "%d",
221 task_tgid_vnr(current));
222 break;
223 /* global pid */
224 case 'P':
225 err = cn_printf(cn, "%d",
226 task_tgid_nr(current));
227 break;
228 case 'i':
229 err = cn_printf(cn, "%d",
230 task_pid_vnr(current));
231 break;
232 case 'I':
233 err = cn_printf(cn, "%d",
234 task_pid_nr(current));
235 break;
236 /* uid */
237 case 'u':
238 err = cn_printf(cn, "%u",
239 from_kuid(&init_user_ns,
240 cred->uid));
241 break;
242 /* gid */
243 case 'g':
244 err = cn_printf(cn, "%u",
245 from_kgid(&init_user_ns,
246 cred->gid));
247 break;
248 case 'd':
249 err = cn_printf(cn, "%d",
250 __get_dumpable(cprm->mm_flags));
251 break;
252 /* signal that caused the coredump */
253 case 's':
254 err = cn_printf(cn, "%d",
255 cprm->siginfo->si_signo);
256 break;
257 /* UNIX time of coredump */
258 case 't': {
259 time64_t time;
260
261 time = ktime_get_real_seconds();
262 err = cn_printf(cn, "%lld", time);
263 break;
264 }
265 /* hostname */
266 case 'h':
267 down_read(&uts_sem);
268 err = cn_esc_printf(cn, "%s",
269 utsname()->nodename);
270 up_read(&uts_sem);
271 break;
272 /* executable */
273 case 'e':
274 err = cn_esc_printf(cn, "%s", current->comm);
275 break;
276 case 'E':
277 err = cn_print_exe_file(cn);
278 break;
279 /* core limit size */
280 case 'c':
281 err = cn_printf(cn, "%lu",
282 rlimit(RLIMIT_CORE));
283 break;
284 default:
285 break;
286 }
287 ++pat_ptr;
288 }
289
290 if (err)
291 return err;
292 }
293
294out:
295 /* Backward compatibility with core_uses_pid:
296 *
297 * If core_pattern does not include a %p (as is the default)
298 * and core_uses_pid is set, then .%pid will be appended to
299 * the filename. Do not do this for piped commands. */
300 if (!ispipe && !pid_in_pattern && core_uses_pid) {
301 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
302 if (err)
303 return err;
304 }
305 return ispipe;
306}
307
308static int zap_process(struct task_struct *start, int exit_code, int flags)
309{
310 struct task_struct *t;
311 int nr = 0;
312
313 /* ignore all signals except SIGKILL, see prepare_signal() */
314 start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
315 start->signal->group_exit_code = exit_code;
316 start->signal->group_stop_count = 0;
317
318 for_each_thread(start, t) {
319 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
320 if (t != current && t->mm) {
321 sigaddset(&t->pending.signal, SIGKILL);
322 signal_wake_up(t, 1);
323 nr++;
324 }
325 }
326
327 return nr;
328}
329
330static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
331 struct core_state *core_state, int exit_code)
332{
333 struct task_struct *g, *p;
334 unsigned long flags;
335 int nr = -EAGAIN;
336
337 spin_lock_irq(&tsk->sighand->siglock);
338 if (!signal_group_exit(tsk->signal)) {
339 mm->core_state = core_state;
340 tsk->signal->group_exit_task = tsk;
341 nr = zap_process(tsk, exit_code, 0);
342 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
343 }
344 spin_unlock_irq(&tsk->sighand->siglock);
345 if (unlikely(nr < 0))
346 return nr;
347
348 tsk->flags |= PF_DUMPCORE;
349 if (atomic_read(&mm->mm_users) == nr + 1)
350 goto done;
351 /*
352 * We should find and kill all tasks which use this mm, and we should
353 * count them correctly into ->nr_threads. We don't take tasklist
354 * lock, but this is safe wrt:
355 *
356 * fork:
357 * None of sub-threads can fork after zap_process(leader). All
358 * processes which were created before this point should be
359 * visible to zap_threads() because copy_process() adds the new
360 * process to the tail of init_task.tasks list, and lock/unlock
361 * of ->siglock provides a memory barrier.
362 *
363 * do_exit:
364 * The caller holds mm->mmap_sem. This means that the task which
365 * uses this mm can't pass exit_mm(), so it can't exit or clear
366 * its ->mm.
367 *
368 * de_thread:
369 * It does list_replace_rcu(&leader->tasks, ¤t->tasks),
370 * we must see either old or new leader, this does not matter.
371 * However, it can change p->sighand, so lock_task_sighand(p)
372 * must be used. Since p->mm != NULL and we hold ->mmap_sem
373 * it can't fail.
374 *
375 * Note also that "g" can be the old leader with ->mm == NULL
376 * and already unhashed and thus removed from ->thread_group.
377 * This is OK, __unhash_process()->list_del_rcu() does not
378 * clear the ->next pointer, we will find the new leader via
379 * next_thread().
380 */
381 rcu_read_lock();
382 for_each_process(g) {
383 if (g == tsk->group_leader)
384 continue;
385 if (g->flags & PF_KTHREAD)
386 continue;
387
388 for_each_thread(g, p) {
389 if (unlikely(!p->mm))
390 continue;
391 if (unlikely(p->mm == mm)) {
392 lock_task_sighand(p, &flags);
393 nr += zap_process(p, exit_code,
394 SIGNAL_GROUP_EXIT);
395 unlock_task_sighand(p, &flags);
396 }
397 break;
398 }
399 }
400 rcu_read_unlock();
401done:
402 atomic_set(&core_state->nr_threads, nr);
403 return nr;
404}
405
406static int coredump_wait(int exit_code, struct core_state *core_state)
407{
408 struct task_struct *tsk = current;
409 struct mm_struct *mm = tsk->mm;
410 int core_waiters = -EBUSY;
411
412 init_completion(&core_state->startup);
413 core_state->dumper.task = tsk;
414 core_state->dumper.next = NULL;
415
416 down_write(&mm->mmap_sem);
417 if (!mm->core_state)
418 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
419 up_write(&mm->mmap_sem);
420
421 if (core_waiters > 0) {
422 struct core_thread *ptr;
423
424 wait_for_completion(&core_state->startup);
425 /*
426 * Wait for all the threads to become inactive, so that
427 * all the thread context (extended register state, like
428 * fpu etc) gets copied to the memory.
429 */
430 ptr = core_state->dumper.next;
431 while (ptr != NULL) {
432 wait_task_inactive(ptr->task, 0);
433 ptr = ptr->next;
434 }
435 }
436
437 return core_waiters;
438}
439
440static void coredump_finish(struct mm_struct *mm, bool core_dumped)
441{
442 struct core_thread *curr, *next;
443 struct task_struct *task;
444
445 spin_lock_irq(¤t->sighand->siglock);
446 if (core_dumped && !__fatal_signal_pending(current))
447 current->signal->group_exit_code |= 0x80;
448 current->signal->group_exit_task = NULL;
449 current->signal->flags = SIGNAL_GROUP_EXIT;
450 spin_unlock_irq(¤t->sighand->siglock);
451
452 next = mm->core_state->dumper.next;
453 while ((curr = next) != NULL) {
454 next = curr->next;
455 task = curr->task;
456 /*
457 * see exit_mm(), curr->task must not see
458 * ->task == NULL before we read ->next.
459 */
460 smp_mb();
461 curr->task = NULL;
462 wake_up_process(task);
463 }
464
465 mm->core_state = NULL;
466}
467
468static bool dump_interrupted(void)
469{
470 /*
471 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
472 * can do try_to_freeze() and check __fatal_signal_pending(),
473 * but then we need to teach dump_write() to restart and clear
474 * TIF_SIGPENDING.
475 */
476 return signal_pending(current);
477}
478
479static void wait_for_dump_helpers(struct file *file)
480{
481 struct pipe_inode_info *pipe = file->private_data;
482
483 pipe_lock(pipe);
484 pipe->readers++;
485 pipe->writers--;
486 wake_up_interruptible_sync(&pipe->wait);
487 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
488 pipe_unlock(pipe);
489
490 /*
491 * We actually want wait_event_freezable() but then we need
492 * to clear TIF_SIGPENDING and improve dump_interrupted().
493 */
494 wait_event_interruptible(pipe->wait, pipe->readers == 1);
495
496 pipe_lock(pipe);
497 pipe->readers--;
498 pipe->writers++;
499 pipe_unlock(pipe);
500}
501
502/*
503 * umh_pipe_setup
504 * helper function to customize the process used
505 * to collect the core in userspace. Specifically
506 * it sets up a pipe and installs it as fd 0 (stdin)
507 * for the process. Returns 0 on success, or
508 * PTR_ERR on failure.
509 * Note that it also sets the core limit to 1. This
510 * is a special value that we use to trap recursive
511 * core dumps
512 */
513static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
514{
515 struct file *files[2];
516 struct coredump_params *cp = (struct coredump_params *)info->data;
517 int err = create_pipe_files(files, 0);
518 if (err)
519 return err;
520
521 cp->file = files[1];
522
523 err = replace_fd(0, files[0], 0);
524 fput(files[0]);
525 /* and disallow core files too */
526 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
527
528 return err;
529}
530
531void do_coredump(const siginfo_t *siginfo)
532{
533 struct core_state core_state;
534 struct core_name cn;
535 struct mm_struct *mm = current->mm;
536 struct linux_binfmt * binfmt;
537 const struct cred *old_cred;
538 struct cred *cred;
539 int retval = 0;
540 int ispipe;
541 struct files_struct *displaced;
542 /* require nonrelative corefile path and be extra careful */
543 bool need_suid_safe = false;
544 bool core_dumped = false;
545 static atomic_t core_dump_count = ATOMIC_INIT(0);
546 struct coredump_params cprm = {
547 .siginfo = siginfo,
548 .regs = signal_pt_regs(),
549 .limit = rlimit(RLIMIT_CORE),
550 /*
551 * We must use the same mm->flags while dumping core to avoid
552 * inconsistency of bit flags, since this flag is not protected
553 * by any locks.
554 */
555 .mm_flags = mm->flags,
556 };
557
558 audit_core_dumps(siginfo->si_signo);
559
560 binfmt = mm->binfmt;
561 if (!binfmt || !binfmt->core_dump)
562 goto fail;
563 if (!__get_dumpable(cprm.mm_flags))
564 goto fail;
565
566 cred = prepare_creds();
567 if (!cred)
568 goto fail;
569 /*
570 * We cannot trust fsuid as being the "true" uid of the process
571 * nor do we know its entire history. We only know it was tainted
572 * so we dump it as root in mode 2, and only into a controlled
573 * environment (pipe handler or fully qualified path).
574 */
575 if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
576 /* Setuid core dump mode */
577 cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */
578 need_suid_safe = true;
579 }
580
581 retval = coredump_wait(siginfo->si_signo, &core_state);
582 if (retval < 0)
583 goto fail_creds;
584
585 old_cred = override_creds(cred);
586
587 ispipe = format_corename(&cn, &cprm);
588
589 if (ispipe) {
590 int dump_count;
591 char **helper_argv;
592 struct subprocess_info *sub_info;
593
594 if (ispipe < 0) {
595 printk(KERN_WARNING "format_corename failed\n");
596 printk(KERN_WARNING "Aborting core\n");
597 goto fail_unlock;
598 }
599
600 if (cprm.limit == 1) {
601 /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
602 *
603 * Normally core limits are irrelevant to pipes, since
604 * we're not writing to the file system, but we use
605 * cprm.limit of 1 here as a special value, this is a
606 * consistent way to catch recursive crashes.
607 * We can still crash if the core_pattern binary sets
608 * RLIM_CORE = !1, but it runs as root, and can do
609 * lots of stupid things.
610 *
611 * Note that we use task_tgid_vnr here to grab the pid
612 * of the process group leader. That way we get the
613 * right pid if a thread in a multi-threaded
614 * core_pattern process dies.
615 */
616 printk(KERN_WARNING
617 "Process %d(%s) has RLIMIT_CORE set to 1\n",
618 task_tgid_vnr(current), current->comm);
619 printk(KERN_WARNING "Aborting core\n");
620 goto fail_unlock;
621 }
622 cprm.limit = RLIM_INFINITY;
623
624 dump_count = atomic_inc_return(&core_dump_count);
625 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
626 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
627 task_tgid_vnr(current), current->comm);
628 printk(KERN_WARNING "Skipping core dump\n");
629 goto fail_dropcount;
630 }
631
632 helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL);
633 if (!helper_argv) {
634 printk(KERN_WARNING "%s failed to allocate memory\n",
635 __func__);
636 goto fail_dropcount;
637 }
638
639 retval = -ENOMEM;
640 sub_info = call_usermodehelper_setup(helper_argv[0],
641 helper_argv, NULL, GFP_KERNEL,
642 umh_pipe_setup, NULL, &cprm);
643 if (sub_info)
644 retval = call_usermodehelper_exec(sub_info,
645 UMH_WAIT_EXEC);
646
647 argv_free(helper_argv);
648 if (retval) {
649 printk(KERN_INFO "Core dump to |%s pipe failed\n",
650 cn.corename);
651 goto close_fail;
652 }
653 } else {
654 struct inode *inode;
655 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
656 O_LARGEFILE | O_EXCL;
657
658 if (cprm.limit < binfmt->min_coredump)
659 goto fail_unlock;
660
661 if (need_suid_safe && cn.corename[0] != '/') {
662 printk(KERN_WARNING "Pid %d(%s) can only dump core "\
663 "to fully qualified path!\n",
664 task_tgid_vnr(current), current->comm);
665 printk(KERN_WARNING "Skipping core dump\n");
666 goto fail_unlock;
667 }
668
669 /*
670 * Unlink the file if it exists unless this is a SUID
671 * binary - in that case, we're running around with root
672 * privs and don't want to unlink another user's coredump.
673 */
674 if (!need_suid_safe) {
675 mm_segment_t old_fs;
676
677 old_fs = get_fs();
678 set_fs(KERNEL_DS);
679 /*
680 * If it doesn't exist, that's fine. If there's some
681 * other problem, we'll catch it at the filp_open().
682 */
683 (void) sys_unlink((const char __user *)cn.corename);
684 set_fs(old_fs);
685 }
686
687 /*
688 * There is a race between unlinking and creating the
689 * file, but if that causes an EEXIST here, that's
690 * fine - another process raced with us while creating
691 * the corefile, and the other process won. To userspace,
692 * what matters is that at least one of the two processes
693 * writes its coredump successfully, not which one.
694 */
695 if (need_suid_safe) {
696 /*
697 * Using user namespaces, normal user tasks can change
698 * their current->fs->root to point to arbitrary
699 * directories. Since the intention of the "only dump
700 * with a fully qualified path" rule is to control where
701 * coredumps may be placed using root privileges,
702 * current->fs->root must not be used. Instead, use the
703 * root directory of init_task.
704 */
705 struct path root;
706
707 task_lock(&init_task);
708 get_fs_root(init_task.fs, &root);
709 task_unlock(&init_task);
710 cprm.file = file_open_root(root.dentry, root.mnt,
711 cn.corename, open_flags, 0600);
712 path_put(&root);
713 } else {
714 cprm.file = filp_open(cn.corename, open_flags, 0600);
715 }
716 if (IS_ERR(cprm.file))
717 goto fail_unlock;
718
719 inode = file_inode(cprm.file);
720 if (inode->i_nlink > 1)
721 goto close_fail;
722 if (d_unhashed(cprm.file->f_path.dentry))
723 goto close_fail;
724 /*
725 * AK: actually i see no reason to not allow this for named
726 * pipes etc, but keep the previous behaviour for now.
727 */
728 if (!S_ISREG(inode->i_mode))
729 goto close_fail;
730 /*
731 * Don't dump core if the filesystem changed owner or mode
732 * of the file during file creation. This is an issue when
733 * a process dumps core while its cwd is e.g. on a vfat
734 * filesystem.
735 */
736 if (!uid_eq(inode->i_uid, current_fsuid()))
737 goto close_fail;
738 if ((inode->i_mode & 0677) != 0600)
739 goto close_fail;
740 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
741 goto close_fail;
742 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
743 goto close_fail;
744 }
745
746 /* get us an unshared descriptor table; almost always a no-op */
747 retval = unshare_files(&displaced);
748 if (retval)
749 goto close_fail;
750 if (displaced)
751 put_files_struct(displaced);
752 if (!dump_interrupted()) {
753 file_start_write(cprm.file);
754 core_dumped = binfmt->core_dump(&cprm);
755 file_end_write(cprm.file);
756 }
757 if (ispipe && core_pipe_limit)
758 wait_for_dump_helpers(cprm.file);
759close_fail:
760 if (cprm.file)
761 filp_close(cprm.file, NULL);
762fail_dropcount:
763 if (ispipe)
764 atomic_dec(&core_dump_count);
765fail_unlock:
766 kfree(cn.corename);
767 coredump_finish(mm, core_dumped);
768 revert_creds(old_cred);
769fail_creds:
770 put_cred(cred);
771fail:
772 return;
773}
774
775/*
776 * Core dumping helper functions. These are the only things you should
777 * do on a core-file: use only these functions to write out all the
778 * necessary info.
779 */
780int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
781{
782 struct file *file = cprm->file;
783 loff_t pos = file->f_pos;
784 ssize_t n;
785 if (cprm->written + nr > cprm->limit)
786 return 0;
787 while (nr) {
788 if (dump_interrupted())
789 return 0;
790 n = __kernel_write(file, addr, nr, &pos);
791 if (n <= 0)
792 return 0;
793 file->f_pos = pos;
794 cprm->written += n;
795 nr -= n;
796 }
797 return 1;
798}
799EXPORT_SYMBOL(dump_emit);
800
801int dump_skip(struct coredump_params *cprm, size_t nr)
802{
803 static char zeroes[PAGE_SIZE];
804 struct file *file = cprm->file;
805 if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
806 if (cprm->written + nr > cprm->limit)
807 return 0;
808 if (dump_interrupted() ||
809 file->f_op->llseek(file, nr, SEEK_CUR) < 0)
810 return 0;
811 cprm->written += nr;
812 return 1;
813 } else {
814 while (nr > PAGE_SIZE) {
815 if (!dump_emit(cprm, zeroes, PAGE_SIZE))
816 return 0;
817 nr -= PAGE_SIZE;
818 }
819 return dump_emit(cprm, zeroes, nr);
820 }
821}
822EXPORT_SYMBOL(dump_skip);
823
824int dump_align(struct coredump_params *cprm, int align)
825{
826 unsigned mod = cprm->written & (align - 1);
827 if (align & (align - 1))
828 return 0;
829 return mod ? dump_skip(cprm, align - mod) : 1;
830}
831EXPORT_SYMBOL(dump_align);
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/slab.h>
3#include <linux/file.h>
4#include <linux/fdtable.h>
5#include <linux/freezer.h>
6#include <linux/mm.h>
7#include <linux/stat.h>
8#include <linux/fcntl.h>
9#include <linux/swap.h>
10#include <linux/ctype.h>
11#include <linux/string.h>
12#include <linux/init.h>
13#include <linux/pagemap.h>
14#include <linux/perf_event.h>
15#include <linux/highmem.h>
16#include <linux/spinlock.h>
17#include <linux/key.h>
18#include <linux/personality.h>
19#include <linux/binfmts.h>
20#include <linux/coredump.h>
21#include <linux/sched/coredump.h>
22#include <linux/sched/signal.h>
23#include <linux/sched/task_stack.h>
24#include <linux/utsname.h>
25#include <linux/pid_namespace.h>
26#include <linux/module.h>
27#include <linux/namei.h>
28#include <linux/mount.h>
29#include <linux/security.h>
30#include <linux/syscalls.h>
31#include <linux/tsacct_kern.h>
32#include <linux/cn_proc.h>
33#include <linux/audit.h>
34#include <linux/tracehook.h>
35#include <linux/kmod.h>
36#include <linux/fsnotify.h>
37#include <linux/fs_struct.h>
38#include <linux/pipe_fs_i.h>
39#include <linux/oom.h>
40#include <linux/compat.h>
41#include <linux/fs.h>
42#include <linux/path.h>
43#include <linux/timekeeping.h>
44
45#include <linux/uaccess.h>
46#include <asm/mmu_context.h>
47#include <asm/tlb.h>
48#include <asm/exec.h>
49
50#include <trace/events/task.h>
51#include "internal.h"
52
53#include <trace/events/sched.h>
54
55int core_uses_pid;
56unsigned int core_pipe_limit;
57char core_pattern[CORENAME_MAX_SIZE] = "core";
58static int core_name_size = CORENAME_MAX_SIZE;
59
60struct core_name {
61 char *corename;
62 int used, size;
63};
64
65/* The maximal length of core_pattern is also specified in sysctl.c */
66
67static int expand_corename(struct core_name *cn, int size)
68{
69 char *corename = krealloc(cn->corename, size, GFP_KERNEL);
70
71 if (!corename)
72 return -ENOMEM;
73
74 if (size > core_name_size) /* racy but harmless */
75 core_name_size = size;
76
77 cn->size = ksize(corename);
78 cn->corename = corename;
79 return 0;
80}
81
82static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
83 va_list arg)
84{
85 int free, need;
86 va_list arg_copy;
87
88again:
89 free = cn->size - cn->used;
90
91 va_copy(arg_copy, arg);
92 need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
93 va_end(arg_copy);
94
95 if (need < free) {
96 cn->used += need;
97 return 0;
98 }
99
100 if (!expand_corename(cn, cn->size + need - free + 1))
101 goto again;
102
103 return -ENOMEM;
104}
105
106static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
107{
108 va_list arg;
109 int ret;
110
111 va_start(arg, fmt);
112 ret = cn_vprintf(cn, fmt, arg);
113 va_end(arg);
114
115 return ret;
116}
117
118static __printf(2, 3)
119int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
120{
121 int cur = cn->used;
122 va_list arg;
123 int ret;
124
125 va_start(arg, fmt);
126 ret = cn_vprintf(cn, fmt, arg);
127 va_end(arg);
128
129 if (ret == 0) {
130 /*
131 * Ensure that this coredump name component can't cause the
132 * resulting corefile path to consist of a ".." or ".".
133 */
134 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
135 (cn->used - cur == 2 && cn->corename[cur] == '.'
136 && cn->corename[cur+1] == '.'))
137 cn->corename[cur] = '!';
138
139 /*
140 * Empty names are fishy and could be used to create a "//" in a
141 * corefile name, causing the coredump to happen one directory
142 * level too high. Enforce that all components of the core
143 * pattern are at least one character long.
144 */
145 if (cn->used == cur)
146 ret = cn_printf(cn, "!");
147 }
148
149 for (; cur < cn->used; ++cur) {
150 if (cn->corename[cur] == '/')
151 cn->corename[cur] = '!';
152 }
153 return ret;
154}
155
156static int cn_print_exe_file(struct core_name *cn, bool name_only)
157{
158 struct file *exe_file;
159 char *pathbuf, *path, *ptr;
160 int ret;
161
162 exe_file = get_mm_exe_file(current->mm);
163 if (!exe_file)
164 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
165
166 pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
167 if (!pathbuf) {
168 ret = -ENOMEM;
169 goto put_exe_file;
170 }
171
172 path = file_path(exe_file, pathbuf, PATH_MAX);
173 if (IS_ERR(path)) {
174 ret = PTR_ERR(path);
175 goto free_buf;
176 }
177
178 if (name_only) {
179 ptr = strrchr(path, '/');
180 if (ptr)
181 path = ptr + 1;
182 }
183 ret = cn_esc_printf(cn, "%s", path);
184
185free_buf:
186 kfree(pathbuf);
187put_exe_file:
188 fput(exe_file);
189 return ret;
190}
191
192/* format_corename will inspect the pattern parameter, and output a
193 * name into corename, which must have space for at least
194 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
195 */
196static int format_corename(struct core_name *cn, struct coredump_params *cprm,
197 size_t **argv, int *argc)
198{
199 const struct cred *cred = current_cred();
200 const char *pat_ptr = core_pattern;
201 int ispipe = (*pat_ptr == '|');
202 bool was_space = false;
203 int pid_in_pattern = 0;
204 int err = 0;
205
206 cn->used = 0;
207 cn->corename = NULL;
208 if (expand_corename(cn, core_name_size))
209 return -ENOMEM;
210 cn->corename[0] = '\0';
211
212 if (ispipe) {
213 int argvs = sizeof(core_pattern) / 2;
214 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
215 if (!(*argv))
216 return -ENOMEM;
217 (*argv)[(*argc)++] = 0;
218 ++pat_ptr;
219 if (!(*pat_ptr))
220 return -ENOMEM;
221 }
222
223 /* Repeat as long as we have more pattern to process and more output
224 space */
225 while (*pat_ptr) {
226 /*
227 * Split on spaces before doing template expansion so that
228 * %e and %E don't get split if they have spaces in them
229 */
230 if (ispipe) {
231 if (isspace(*pat_ptr)) {
232 was_space = true;
233 pat_ptr++;
234 continue;
235 } else if (was_space) {
236 was_space = false;
237 err = cn_printf(cn, "%c", '\0');
238 if (err)
239 return err;
240 (*argv)[(*argc)++] = cn->used;
241 }
242 }
243 if (*pat_ptr != '%') {
244 err = cn_printf(cn, "%c", *pat_ptr++);
245 } else {
246 switch (*++pat_ptr) {
247 /* single % at the end, drop that */
248 case 0:
249 goto out;
250 /* Double percent, output one percent */
251 case '%':
252 err = cn_printf(cn, "%c", '%');
253 break;
254 /* pid */
255 case 'p':
256 pid_in_pattern = 1;
257 err = cn_printf(cn, "%d",
258 task_tgid_vnr(current));
259 break;
260 /* global pid */
261 case 'P':
262 err = cn_printf(cn, "%d",
263 task_tgid_nr(current));
264 break;
265 case 'i':
266 err = cn_printf(cn, "%d",
267 task_pid_vnr(current));
268 break;
269 case 'I':
270 err = cn_printf(cn, "%d",
271 task_pid_nr(current));
272 break;
273 /* uid */
274 case 'u':
275 err = cn_printf(cn, "%u",
276 from_kuid(&init_user_ns,
277 cred->uid));
278 break;
279 /* gid */
280 case 'g':
281 err = cn_printf(cn, "%u",
282 from_kgid(&init_user_ns,
283 cred->gid));
284 break;
285 case 'd':
286 err = cn_printf(cn, "%d",
287 __get_dumpable(cprm->mm_flags));
288 break;
289 /* signal that caused the coredump */
290 case 's':
291 err = cn_printf(cn, "%d",
292 cprm->siginfo->si_signo);
293 break;
294 /* UNIX time of coredump */
295 case 't': {
296 time64_t time;
297
298 time = ktime_get_real_seconds();
299 err = cn_printf(cn, "%lld", time);
300 break;
301 }
302 /* hostname */
303 case 'h':
304 down_read(&uts_sem);
305 err = cn_esc_printf(cn, "%s",
306 utsname()->nodename);
307 up_read(&uts_sem);
308 break;
309 /* executable, could be changed by prctl PR_SET_NAME etc */
310 case 'e':
311 err = cn_esc_printf(cn, "%s", current->comm);
312 break;
313 /* file name of executable */
314 case 'f':
315 err = cn_print_exe_file(cn, true);
316 break;
317 case 'E':
318 err = cn_print_exe_file(cn, false);
319 break;
320 /* core limit size */
321 case 'c':
322 err = cn_printf(cn, "%lu",
323 rlimit(RLIMIT_CORE));
324 break;
325 default:
326 break;
327 }
328 ++pat_ptr;
329 }
330
331 if (err)
332 return err;
333 }
334
335out:
336 /* Backward compatibility with core_uses_pid:
337 *
338 * If core_pattern does not include a %p (as is the default)
339 * and core_uses_pid is set, then .%pid will be appended to
340 * the filename. Do not do this for piped commands. */
341 if (!ispipe && !pid_in_pattern && core_uses_pid) {
342 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
343 if (err)
344 return err;
345 }
346 return ispipe;
347}
348
349static int zap_process(struct task_struct *start, int exit_code, int flags)
350{
351 struct task_struct *t;
352 int nr = 0;
353
354 /* ignore all signals except SIGKILL, see prepare_signal() */
355 start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
356 start->signal->group_exit_code = exit_code;
357 start->signal->group_stop_count = 0;
358
359 for_each_thread(start, t) {
360 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
361 if (t != current && t->mm) {
362 sigaddset(&t->pending.signal, SIGKILL);
363 signal_wake_up(t, 1);
364 nr++;
365 }
366 }
367
368 return nr;
369}
370
371static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
372 struct core_state *core_state, int exit_code)
373{
374 struct task_struct *g, *p;
375 unsigned long flags;
376 int nr = -EAGAIN;
377
378 spin_lock_irq(&tsk->sighand->siglock);
379 if (!signal_group_exit(tsk->signal)) {
380 mm->core_state = core_state;
381 tsk->signal->group_exit_task = tsk;
382 nr = zap_process(tsk, exit_code, 0);
383 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
384 }
385 spin_unlock_irq(&tsk->sighand->siglock);
386 if (unlikely(nr < 0))
387 return nr;
388
389 tsk->flags |= PF_DUMPCORE;
390 if (atomic_read(&mm->mm_users) == nr + 1)
391 goto done;
392 /*
393 * We should find and kill all tasks which use this mm, and we should
394 * count them correctly into ->nr_threads. We don't take tasklist
395 * lock, but this is safe wrt:
396 *
397 * fork:
398 * None of sub-threads can fork after zap_process(leader). All
399 * processes which were created before this point should be
400 * visible to zap_threads() because copy_process() adds the new
401 * process to the tail of init_task.tasks list, and lock/unlock
402 * of ->siglock provides a memory barrier.
403 *
404 * do_exit:
405 * The caller holds mm->mmap_lock. This means that the task which
406 * uses this mm can't pass exit_mm(), so it can't exit or clear
407 * its ->mm.
408 *
409 * de_thread:
410 * It does list_replace_rcu(&leader->tasks, ¤t->tasks),
411 * we must see either old or new leader, this does not matter.
412 * However, it can change p->sighand, so lock_task_sighand(p)
413 * must be used. Since p->mm != NULL and we hold ->mmap_lock
414 * it can't fail.
415 *
416 * Note also that "g" can be the old leader with ->mm == NULL
417 * and already unhashed and thus removed from ->thread_group.
418 * This is OK, __unhash_process()->list_del_rcu() does not
419 * clear the ->next pointer, we will find the new leader via
420 * next_thread().
421 */
422 rcu_read_lock();
423 for_each_process(g) {
424 if (g == tsk->group_leader)
425 continue;
426 if (g->flags & PF_KTHREAD)
427 continue;
428
429 for_each_thread(g, p) {
430 if (unlikely(!p->mm))
431 continue;
432 if (unlikely(p->mm == mm)) {
433 lock_task_sighand(p, &flags);
434 nr += zap_process(p, exit_code,
435 SIGNAL_GROUP_EXIT);
436 unlock_task_sighand(p, &flags);
437 }
438 break;
439 }
440 }
441 rcu_read_unlock();
442done:
443 atomic_set(&core_state->nr_threads, nr);
444 return nr;
445}
446
447static int coredump_wait(int exit_code, struct core_state *core_state)
448{
449 struct task_struct *tsk = current;
450 struct mm_struct *mm = tsk->mm;
451 int core_waiters = -EBUSY;
452
453 init_completion(&core_state->startup);
454 core_state->dumper.task = tsk;
455 core_state->dumper.next = NULL;
456
457 if (mmap_write_lock_killable(mm))
458 return -EINTR;
459
460 if (!mm->core_state)
461 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
462 mmap_write_unlock(mm);
463
464 if (core_waiters > 0) {
465 struct core_thread *ptr;
466
467 freezer_do_not_count();
468 wait_for_completion(&core_state->startup);
469 freezer_count();
470 /*
471 * Wait for all the threads to become inactive, so that
472 * all the thread context (extended register state, like
473 * fpu etc) gets copied to the memory.
474 */
475 ptr = core_state->dumper.next;
476 while (ptr != NULL) {
477 wait_task_inactive(ptr->task, 0);
478 ptr = ptr->next;
479 }
480 }
481
482 return core_waiters;
483}
484
485static void coredump_finish(struct mm_struct *mm, bool core_dumped)
486{
487 struct core_thread *curr, *next;
488 struct task_struct *task;
489
490 spin_lock_irq(¤t->sighand->siglock);
491 if (core_dumped && !__fatal_signal_pending(current))
492 current->signal->group_exit_code |= 0x80;
493 current->signal->group_exit_task = NULL;
494 current->signal->flags = SIGNAL_GROUP_EXIT;
495 spin_unlock_irq(¤t->sighand->siglock);
496
497 next = mm->core_state->dumper.next;
498 while ((curr = next) != NULL) {
499 next = curr->next;
500 task = curr->task;
501 /*
502 * see exit_mm(), curr->task must not see
503 * ->task == NULL before we read ->next.
504 */
505 smp_mb();
506 curr->task = NULL;
507 wake_up_process(task);
508 }
509
510 mm->core_state = NULL;
511}
512
513static bool dump_interrupted(void)
514{
515 /*
516 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
517 * can do try_to_freeze() and check __fatal_signal_pending(),
518 * but then we need to teach dump_write() to restart and clear
519 * TIF_SIGPENDING.
520 */
521 return signal_pending(current);
522}
523
524static void wait_for_dump_helpers(struct file *file)
525{
526 struct pipe_inode_info *pipe = file->private_data;
527
528 pipe_lock(pipe);
529 pipe->readers++;
530 pipe->writers--;
531 wake_up_interruptible_sync(&pipe->rd_wait);
532 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
533 pipe_unlock(pipe);
534
535 /*
536 * We actually want wait_event_freezable() but then we need
537 * to clear TIF_SIGPENDING and improve dump_interrupted().
538 */
539 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
540
541 pipe_lock(pipe);
542 pipe->readers--;
543 pipe->writers++;
544 pipe_unlock(pipe);
545}
546
547/*
548 * umh_pipe_setup
549 * helper function to customize the process used
550 * to collect the core in userspace. Specifically
551 * it sets up a pipe and installs it as fd 0 (stdin)
552 * for the process. Returns 0 on success, or
553 * PTR_ERR on failure.
554 * Note that it also sets the core limit to 1. This
555 * is a special value that we use to trap recursive
556 * core dumps
557 */
558static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
559{
560 struct file *files[2];
561 struct coredump_params *cp = (struct coredump_params *)info->data;
562 int err = create_pipe_files(files, 0);
563 if (err)
564 return err;
565
566 cp->file = files[1];
567
568 err = replace_fd(0, files[0], 0);
569 fput(files[0]);
570 /* and disallow core files too */
571 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
572
573 return err;
574}
575
576void do_coredump(const kernel_siginfo_t *siginfo)
577{
578 struct core_state core_state;
579 struct core_name cn;
580 struct mm_struct *mm = current->mm;
581 struct linux_binfmt * binfmt;
582 const struct cred *old_cred;
583 struct cred *cred;
584 int retval = 0;
585 int ispipe;
586 size_t *argv = NULL;
587 int argc = 0;
588 struct files_struct *displaced;
589 /* require nonrelative corefile path and be extra careful */
590 bool need_suid_safe = false;
591 bool core_dumped = false;
592 static atomic_t core_dump_count = ATOMIC_INIT(0);
593 struct coredump_params cprm = {
594 .siginfo = siginfo,
595 .regs = signal_pt_regs(),
596 .limit = rlimit(RLIMIT_CORE),
597 /*
598 * We must use the same mm->flags while dumping core to avoid
599 * inconsistency of bit flags, since this flag is not protected
600 * by any locks.
601 */
602 .mm_flags = mm->flags,
603 };
604
605 audit_core_dumps(siginfo->si_signo);
606
607 binfmt = mm->binfmt;
608 if (!binfmt || !binfmt->core_dump)
609 goto fail;
610 if (!__get_dumpable(cprm.mm_flags))
611 goto fail;
612
613 cred = prepare_creds();
614 if (!cred)
615 goto fail;
616 /*
617 * We cannot trust fsuid as being the "true" uid of the process
618 * nor do we know its entire history. We only know it was tainted
619 * so we dump it as root in mode 2, and only into a controlled
620 * environment (pipe handler or fully qualified path).
621 */
622 if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
623 /* Setuid core dump mode */
624 cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */
625 need_suid_safe = true;
626 }
627
628 retval = coredump_wait(siginfo->si_signo, &core_state);
629 if (retval < 0)
630 goto fail_creds;
631
632 old_cred = override_creds(cred);
633
634 ispipe = format_corename(&cn, &cprm, &argv, &argc);
635
636 if (ispipe) {
637 int argi;
638 int dump_count;
639 char **helper_argv;
640 struct subprocess_info *sub_info;
641
642 if (ispipe < 0) {
643 printk(KERN_WARNING "format_corename failed\n");
644 printk(KERN_WARNING "Aborting core\n");
645 goto fail_unlock;
646 }
647
648 if (cprm.limit == 1) {
649 /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
650 *
651 * Normally core limits are irrelevant to pipes, since
652 * we're not writing to the file system, but we use
653 * cprm.limit of 1 here as a special value, this is a
654 * consistent way to catch recursive crashes.
655 * We can still crash if the core_pattern binary sets
656 * RLIM_CORE = !1, but it runs as root, and can do
657 * lots of stupid things.
658 *
659 * Note that we use task_tgid_vnr here to grab the pid
660 * of the process group leader. That way we get the
661 * right pid if a thread in a multi-threaded
662 * core_pattern process dies.
663 */
664 printk(KERN_WARNING
665 "Process %d(%s) has RLIMIT_CORE set to 1\n",
666 task_tgid_vnr(current), current->comm);
667 printk(KERN_WARNING "Aborting core\n");
668 goto fail_unlock;
669 }
670 cprm.limit = RLIM_INFINITY;
671
672 dump_count = atomic_inc_return(&core_dump_count);
673 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
674 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
675 task_tgid_vnr(current), current->comm);
676 printk(KERN_WARNING "Skipping core dump\n");
677 goto fail_dropcount;
678 }
679
680 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
681 GFP_KERNEL);
682 if (!helper_argv) {
683 printk(KERN_WARNING "%s failed to allocate memory\n",
684 __func__);
685 goto fail_dropcount;
686 }
687 for (argi = 0; argi < argc; argi++)
688 helper_argv[argi] = cn.corename + argv[argi];
689 helper_argv[argi] = NULL;
690
691 retval = -ENOMEM;
692 sub_info = call_usermodehelper_setup(helper_argv[0],
693 helper_argv, NULL, GFP_KERNEL,
694 umh_pipe_setup, NULL, &cprm);
695 if (sub_info)
696 retval = call_usermodehelper_exec(sub_info,
697 UMH_WAIT_EXEC);
698
699 kfree(helper_argv);
700 if (retval) {
701 printk(KERN_INFO "Core dump to |%s pipe failed\n",
702 cn.corename);
703 goto close_fail;
704 }
705 } else {
706 struct inode *inode;
707 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
708 O_LARGEFILE | O_EXCL;
709
710 if (cprm.limit < binfmt->min_coredump)
711 goto fail_unlock;
712
713 if (need_suid_safe && cn.corename[0] != '/') {
714 printk(KERN_WARNING "Pid %d(%s) can only dump core "\
715 "to fully qualified path!\n",
716 task_tgid_vnr(current), current->comm);
717 printk(KERN_WARNING "Skipping core dump\n");
718 goto fail_unlock;
719 }
720
721 /*
722 * Unlink the file if it exists unless this is a SUID
723 * binary - in that case, we're running around with root
724 * privs and don't want to unlink another user's coredump.
725 */
726 if (!need_suid_safe) {
727 /*
728 * If it doesn't exist, that's fine. If there's some
729 * other problem, we'll catch it at the filp_open().
730 */
731 do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
732 }
733
734 /*
735 * There is a race between unlinking and creating the
736 * file, but if that causes an EEXIST here, that's
737 * fine - another process raced with us while creating
738 * the corefile, and the other process won. To userspace,
739 * what matters is that at least one of the two processes
740 * writes its coredump successfully, not which one.
741 */
742 if (need_suid_safe) {
743 /*
744 * Using user namespaces, normal user tasks can change
745 * their current->fs->root to point to arbitrary
746 * directories. Since the intention of the "only dump
747 * with a fully qualified path" rule is to control where
748 * coredumps may be placed using root privileges,
749 * current->fs->root must not be used. Instead, use the
750 * root directory of init_task.
751 */
752 struct path root;
753
754 task_lock(&init_task);
755 get_fs_root(init_task.fs, &root);
756 task_unlock(&init_task);
757 cprm.file = file_open_root(root.dentry, root.mnt,
758 cn.corename, open_flags, 0600);
759 path_put(&root);
760 } else {
761 cprm.file = filp_open(cn.corename, open_flags, 0600);
762 }
763 if (IS_ERR(cprm.file))
764 goto fail_unlock;
765
766 inode = file_inode(cprm.file);
767 if (inode->i_nlink > 1)
768 goto close_fail;
769 if (d_unhashed(cprm.file->f_path.dentry))
770 goto close_fail;
771 /*
772 * AK: actually i see no reason to not allow this for named
773 * pipes etc, but keep the previous behaviour for now.
774 */
775 if (!S_ISREG(inode->i_mode))
776 goto close_fail;
777 /*
778 * Don't dump core if the filesystem changed owner or mode
779 * of the file during file creation. This is an issue when
780 * a process dumps core while its cwd is e.g. on a vfat
781 * filesystem.
782 */
783 if (!uid_eq(inode->i_uid, current_fsuid()))
784 goto close_fail;
785 if ((inode->i_mode & 0677) != 0600)
786 goto close_fail;
787 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
788 goto close_fail;
789 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
790 goto close_fail;
791 }
792
793 /* get us an unshared descriptor table; almost always a no-op */
794 retval = unshare_files(&displaced);
795 if (retval)
796 goto close_fail;
797 if (displaced)
798 put_files_struct(displaced);
799 if (!dump_interrupted()) {
800 /*
801 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
802 * have this set to NULL.
803 */
804 if (!cprm.file) {
805 pr_info("Core dump to |%s disabled\n", cn.corename);
806 goto close_fail;
807 }
808 file_start_write(cprm.file);
809 core_dumped = binfmt->core_dump(&cprm);
810 file_end_write(cprm.file);
811 }
812 if (ispipe && core_pipe_limit)
813 wait_for_dump_helpers(cprm.file);
814close_fail:
815 if (cprm.file)
816 filp_close(cprm.file, NULL);
817fail_dropcount:
818 if (ispipe)
819 atomic_dec(&core_dump_count);
820fail_unlock:
821 kfree(argv);
822 kfree(cn.corename);
823 coredump_finish(mm, core_dumped);
824 revert_creds(old_cred);
825fail_creds:
826 put_cred(cred);
827fail:
828 return;
829}
830
831/*
832 * Core dumping helper functions. These are the only things you should
833 * do on a core-file: use only these functions to write out all the
834 * necessary info.
835 */
836int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
837{
838 struct file *file = cprm->file;
839 loff_t pos = file->f_pos;
840 ssize_t n;
841 if (cprm->written + nr > cprm->limit)
842 return 0;
843 while (nr) {
844 if (dump_interrupted())
845 return 0;
846 n = __kernel_write(file, addr, nr, &pos);
847 if (n <= 0)
848 return 0;
849 file->f_pos = pos;
850 cprm->written += n;
851 cprm->pos += n;
852 nr -= n;
853 }
854 return 1;
855}
856EXPORT_SYMBOL(dump_emit);
857
858int dump_skip(struct coredump_params *cprm, size_t nr)
859{
860 static char zeroes[PAGE_SIZE];
861 struct file *file = cprm->file;
862 if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
863 if (dump_interrupted() ||
864 file->f_op->llseek(file, nr, SEEK_CUR) < 0)
865 return 0;
866 cprm->pos += nr;
867 return 1;
868 } else {
869 while (nr > PAGE_SIZE) {
870 if (!dump_emit(cprm, zeroes, PAGE_SIZE))
871 return 0;
872 nr -= PAGE_SIZE;
873 }
874 return dump_emit(cprm, zeroes, nr);
875 }
876}
877EXPORT_SYMBOL(dump_skip);
878
879int dump_align(struct coredump_params *cprm, int align)
880{
881 unsigned mod = cprm->pos & (align - 1);
882 if (align & (align - 1))
883 return 0;
884 return mod ? dump_skip(cprm, align - mod) : 1;
885}
886EXPORT_SYMBOL(dump_align);
887
888/*
889 * Ensures that file size is big enough to contain the current file
890 * postion. This prevents gdb from complaining about a truncated file
891 * if the last "write" to the file was dump_skip.
892 */
893void dump_truncate(struct coredump_params *cprm)
894{
895 struct file *file = cprm->file;
896 loff_t offset;
897
898 if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
899 offset = file->f_op->llseek(file, 0, SEEK_CUR);
900 if (i_size_read(file->f_mapping->host) < offset)
901 do_truncate(file->f_path.dentry, offset, 0, file);
902 }
903}
904EXPORT_SYMBOL(dump_truncate);