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