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 #include <linux/elf.h>
45
46 #include <linux/uaccess.h>
47 #include <asm/mmu_context.h>
48 #include <asm/tlb.h>
49 #include <asm/exec.h>
50
51 #include <trace/events/task.h>
52 #include "internal.h"
53
54 #include <trace/events/sched.h>
55
56 static bool dump_vma_snapshot(struct coredump_params *cprm);
57 static void free_vma_snapshot(struct coredump_params *cprm);
58
59 int core_uses_pid;
60 unsigned int core_pipe_limit;
61 char core_pattern[CORENAME_MAX_SIZE] = "core";
62 static int core_name_size = CORENAME_MAX_SIZE;
63
64 struct core_name {
65 char *corename;
66 int used, size;
67 };
68
69 /* The maximal length of core_pattern is also specified in sysctl.c */
70
expand_corename(struct core_name * cn,int size)71 static int expand_corename(struct core_name *cn, int size)
72 {
73 char *corename = krealloc(cn->corename, size, GFP_KERNEL);
74
75 if (!corename)
76 return -ENOMEM;
77
78 if (size > core_name_size) /* racy but harmless */
79 core_name_size = size;
80
81 cn->size = ksize(corename);
82 cn->corename = corename;
83 return 0;
84 }
85
cn_vprintf(struct core_name * cn,const char * fmt,va_list arg)86 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
87 va_list arg)
88 {
89 int free, need;
90 va_list arg_copy;
91
92 again:
93 free = cn->size - cn->used;
94
95 va_copy(arg_copy, arg);
96 need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
97 va_end(arg_copy);
98
99 if (need < free) {
100 cn->used += need;
101 return 0;
102 }
103
104 if (!expand_corename(cn, cn->size + need - free + 1))
105 goto again;
106
107 return -ENOMEM;
108 }
109
cn_printf(struct core_name * cn,const char * fmt,...)110 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
111 {
112 va_list arg;
113 int ret;
114
115 va_start(arg, fmt);
116 ret = cn_vprintf(cn, fmt, arg);
117 va_end(arg);
118
119 return ret;
120 }
121
122 static __printf(2, 3)
cn_esc_printf(struct core_name * cn,const char * fmt,...)123 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
124 {
125 int cur = cn->used;
126 va_list arg;
127 int ret;
128
129 va_start(arg, fmt);
130 ret = cn_vprintf(cn, fmt, arg);
131 va_end(arg);
132
133 if (ret == 0) {
134 /*
135 * Ensure that this coredump name component can't cause the
136 * resulting corefile path to consist of a ".." or ".".
137 */
138 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
139 (cn->used - cur == 2 && cn->corename[cur] == '.'
140 && cn->corename[cur+1] == '.'))
141 cn->corename[cur] = '!';
142
143 /*
144 * Empty names are fishy and could be used to create a "//" in a
145 * corefile name, causing the coredump to happen one directory
146 * level too high. Enforce that all components of the core
147 * pattern are at least one character long.
148 */
149 if (cn->used == cur)
150 ret = cn_printf(cn, "!");
151 }
152
153 for (; cur < cn->used; ++cur) {
154 if (cn->corename[cur] == '/')
155 cn->corename[cur] = '!';
156 }
157 return ret;
158 }
159
cn_print_exe_file(struct core_name * cn,bool name_only)160 static int cn_print_exe_file(struct core_name *cn, bool name_only)
161 {
162 struct file *exe_file;
163 char *pathbuf, *path, *ptr;
164 int ret;
165
166 exe_file = get_mm_exe_file(current->mm);
167 if (!exe_file)
168 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
169
170 pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
171 if (!pathbuf) {
172 ret = -ENOMEM;
173 goto put_exe_file;
174 }
175
176 path = file_path(exe_file, pathbuf, PATH_MAX);
177 if (IS_ERR(path)) {
178 ret = PTR_ERR(path);
179 goto free_buf;
180 }
181
182 if (name_only) {
183 ptr = strrchr(path, '/');
184 if (ptr)
185 path = ptr + 1;
186 }
187 ret = cn_esc_printf(cn, "%s", path);
188
189 free_buf:
190 kfree(pathbuf);
191 put_exe_file:
192 fput(exe_file);
193 return ret;
194 }
195
196 /* format_corename will inspect the pattern parameter, and output a
197 * name into corename, which must have space for at least
198 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
199 */
format_corename(struct core_name * cn,struct coredump_params * cprm,size_t ** argv,int * argc)200 static int format_corename(struct core_name *cn, struct coredump_params *cprm,
201 size_t **argv, int *argc)
202 {
203 const struct cred *cred = current_cred();
204 const char *pat_ptr = core_pattern;
205 int ispipe = (*pat_ptr == '|');
206 bool was_space = false;
207 int pid_in_pattern = 0;
208 int err = 0;
209
210 cn->used = 0;
211 cn->corename = NULL;
212 if (expand_corename(cn, core_name_size))
213 return -ENOMEM;
214 cn->corename[0] = '\0';
215
216 if (ispipe) {
217 int argvs = sizeof(core_pattern) / 2;
218 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
219 if (!(*argv))
220 return -ENOMEM;
221 (*argv)[(*argc)++] = 0;
222 ++pat_ptr;
223 if (!(*pat_ptr))
224 return -ENOMEM;
225 }
226
227 /* Repeat as long as we have more pattern to process and more output
228 space */
229 while (*pat_ptr) {
230 /*
231 * Split on spaces before doing template expansion so that
232 * %e and %E don't get split if they have spaces in them
233 */
234 if (ispipe) {
235 if (isspace(*pat_ptr)) {
236 if (cn->used != 0)
237 was_space = true;
238 pat_ptr++;
239 continue;
240 } else if (was_space) {
241 was_space = false;
242 err = cn_printf(cn, "%c", '\0');
243 if (err)
244 return err;
245 (*argv)[(*argc)++] = cn->used;
246 }
247 }
248 if (*pat_ptr != '%') {
249 err = cn_printf(cn, "%c", *pat_ptr++);
250 } else {
251 switch (*++pat_ptr) {
252 /* single % at the end, drop that */
253 case 0:
254 goto out;
255 /* Double percent, output one percent */
256 case '%':
257 err = cn_printf(cn, "%c", '%');
258 break;
259 /* pid */
260 case 'p':
261 pid_in_pattern = 1;
262 err = cn_printf(cn, "%d",
263 task_tgid_vnr(current));
264 break;
265 /* global pid */
266 case 'P':
267 err = cn_printf(cn, "%d",
268 task_tgid_nr(current));
269 break;
270 case 'i':
271 err = cn_printf(cn, "%d",
272 task_pid_vnr(current));
273 break;
274 case 'I':
275 err = cn_printf(cn, "%d",
276 task_pid_nr(current));
277 break;
278 /* uid */
279 case 'u':
280 err = cn_printf(cn, "%u",
281 from_kuid(&init_user_ns,
282 cred->uid));
283 break;
284 /* gid */
285 case 'g':
286 err = cn_printf(cn, "%u",
287 from_kgid(&init_user_ns,
288 cred->gid));
289 break;
290 case 'd':
291 err = cn_printf(cn, "%d",
292 __get_dumpable(cprm->mm_flags));
293 break;
294 /* signal that caused the coredump */
295 case 's':
296 err = cn_printf(cn, "%d",
297 cprm->siginfo->si_signo);
298 break;
299 /* UNIX time of coredump */
300 case 't': {
301 time64_t time;
302
303 time = ktime_get_real_seconds();
304 err = cn_printf(cn, "%lld", time);
305 break;
306 }
307 /* hostname */
308 case 'h':
309 down_read(&uts_sem);
310 err = cn_esc_printf(cn, "%s",
311 utsname()->nodename);
312 up_read(&uts_sem);
313 break;
314 /* executable, could be changed by prctl PR_SET_NAME etc */
315 case 'e':
316 err = cn_esc_printf(cn, "%s", current->comm);
317 break;
318 /* file name of executable */
319 case 'f':
320 err = cn_print_exe_file(cn, true);
321 break;
322 case 'E':
323 err = cn_print_exe_file(cn, false);
324 break;
325 /* core limit size */
326 case 'c':
327 err = cn_printf(cn, "%lu",
328 rlimit(RLIMIT_CORE));
329 break;
330 default:
331 break;
332 }
333 ++pat_ptr;
334 }
335
336 if (err)
337 return err;
338 }
339
340 out:
341 /* Backward compatibility with core_uses_pid:
342 *
343 * If core_pattern does not include a %p (as is the default)
344 * and core_uses_pid is set, then .%pid will be appended to
345 * the filename. Do not do this for piped commands. */
346 if (!ispipe && !pid_in_pattern && core_uses_pid) {
347 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
348 if (err)
349 return err;
350 }
351 return ispipe;
352 }
353
zap_process(struct task_struct * start,int exit_code,int flags)354 static int zap_process(struct task_struct *start, int exit_code, int flags)
355 {
356 struct task_struct *t;
357 int nr = 0;
358
359 /* ignore all signals except SIGKILL, see prepare_signal() */
360 start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
361 start->signal->group_exit_code = exit_code;
362 start->signal->group_stop_count = 0;
363
364 for_each_thread(start, t) {
365 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
366 if (t != current && t->mm) {
367 sigaddset(&t->pending.signal, SIGKILL);
368 signal_wake_up(t, 1);
369 nr++;
370 }
371 }
372
373 return nr;
374 }
375
zap_threads(struct task_struct * tsk,struct mm_struct * mm,struct core_state * core_state,int exit_code)376 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
377 struct core_state *core_state, int exit_code)
378 {
379 struct task_struct *g, *p;
380 unsigned long flags;
381 int nr = -EAGAIN;
382
383 spin_lock_irq(&tsk->sighand->siglock);
384 if (!signal_group_exit(tsk->signal)) {
385 mm->core_state = core_state;
386 tsk->signal->group_exit_task = tsk;
387 nr = zap_process(tsk, exit_code, 0);
388 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
389 }
390 spin_unlock_irq(&tsk->sighand->siglock);
391 if (unlikely(nr < 0))
392 return nr;
393
394 tsk->flags |= PF_DUMPCORE;
395 if (atomic_read(&mm->mm_users) == nr + 1)
396 goto done;
397 /*
398 * We should find and kill all tasks which use this mm, and we should
399 * count them correctly into ->nr_threads. We don't take tasklist
400 * lock, but this is safe wrt:
401 *
402 * fork:
403 * None of sub-threads can fork after zap_process(leader). All
404 * processes which were created before this point should be
405 * visible to zap_threads() because copy_process() adds the new
406 * process to the tail of init_task.tasks list, and lock/unlock
407 * of ->siglock provides a memory barrier.
408 *
409 * do_exit:
410 * The caller holds mm->mmap_lock. This means that the task which
411 * uses this mm can't pass exit_mm(), so it can't exit or clear
412 * its ->mm.
413 *
414 * de_thread:
415 * It does list_replace_rcu(&leader->tasks, ¤t->tasks),
416 * we must see either old or new leader, this does not matter.
417 * However, it can change p->sighand, so lock_task_sighand(p)
418 * must be used. Since p->mm != NULL and we hold ->mmap_lock
419 * it can't fail.
420 *
421 * Note also that "g" can be the old leader with ->mm == NULL
422 * and already unhashed and thus removed from ->thread_group.
423 * This is OK, __unhash_process()->list_del_rcu() does not
424 * clear the ->next pointer, we will find the new leader via
425 * next_thread().
426 */
427 rcu_read_lock();
428 for_each_process(g) {
429 if (g == tsk->group_leader)
430 continue;
431 if (g->flags & PF_KTHREAD)
432 continue;
433
434 for_each_thread(g, p) {
435 if (unlikely(!p->mm))
436 continue;
437 if (unlikely(p->mm == mm)) {
438 lock_task_sighand(p, &flags);
439 nr += zap_process(p, exit_code,
440 SIGNAL_GROUP_EXIT);
441 unlock_task_sighand(p, &flags);
442 }
443 break;
444 }
445 }
446 rcu_read_unlock();
447 done:
448 atomic_set(&core_state->nr_threads, nr);
449 return nr;
450 }
451
coredump_wait(int exit_code,struct core_state * core_state)452 static int coredump_wait(int exit_code, struct core_state *core_state)
453 {
454 struct task_struct *tsk = current;
455 struct mm_struct *mm = tsk->mm;
456 int core_waiters = -EBUSY;
457
458 init_completion(&core_state->startup);
459 core_state->dumper.task = tsk;
460 core_state->dumper.next = NULL;
461
462 if (mmap_write_lock_killable(mm))
463 return -EINTR;
464
465 if (!mm->core_state)
466 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
467 mmap_write_unlock(mm);
468
469 if (core_waiters > 0) {
470 struct core_thread *ptr;
471
472 freezer_do_not_count();
473 wait_for_completion(&core_state->startup);
474 freezer_count();
475 /*
476 * Wait for all the threads to become inactive, so that
477 * all the thread context (extended register state, like
478 * fpu etc) gets copied to the memory.
479 */
480 ptr = core_state->dumper.next;
481 while (ptr != NULL) {
482 wait_task_inactive(ptr->task, 0);
483 ptr = ptr->next;
484 }
485 }
486
487 return core_waiters;
488 }
489
coredump_finish(struct mm_struct * mm,bool core_dumped)490 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
491 {
492 struct core_thread *curr, *next;
493 struct task_struct *task;
494
495 spin_lock_irq(¤t->sighand->siglock);
496 if (core_dumped && !__fatal_signal_pending(current))
497 current->signal->group_exit_code |= 0x80;
498 current->signal->group_exit_task = NULL;
499 current->signal->flags = SIGNAL_GROUP_EXIT;
500 spin_unlock_irq(¤t->sighand->siglock);
501
502 next = mm->core_state->dumper.next;
503 while ((curr = next) != NULL) {
504 next = curr->next;
505 task = curr->task;
506 /*
507 * see exit_mm(), curr->task must not see
508 * ->task == NULL before we read ->next.
509 */
510 smp_mb();
511 curr->task = NULL;
512 wake_up_process(task);
513 }
514
515 mm->core_state = NULL;
516 }
517
dump_interrupted(void)518 static bool dump_interrupted(void)
519 {
520 /*
521 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
522 * can do try_to_freeze() and check __fatal_signal_pending(),
523 * but then we need to teach dump_write() to restart and clear
524 * TIF_SIGPENDING.
525 */
526 return fatal_signal_pending(current) || freezing(current);
527 }
528
wait_for_dump_helpers(struct file * file)529 static void wait_for_dump_helpers(struct file *file)
530 {
531 struct pipe_inode_info *pipe = file->private_data;
532
533 pipe_lock(pipe);
534 pipe->readers++;
535 pipe->writers--;
536 wake_up_interruptible_sync(&pipe->rd_wait);
537 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
538 pipe_unlock(pipe);
539
540 /*
541 * We actually want wait_event_freezable() but then we need
542 * to clear TIF_SIGPENDING and improve dump_interrupted().
543 */
544 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
545
546 pipe_lock(pipe);
547 pipe->readers--;
548 pipe->writers++;
549 pipe_unlock(pipe);
550 }
551
552 /*
553 * umh_pipe_setup
554 * helper function to customize the process used
555 * to collect the core in userspace. Specifically
556 * it sets up a pipe and installs it as fd 0 (stdin)
557 * for the process. Returns 0 on success, or
558 * PTR_ERR on failure.
559 * Note that it also sets the core limit to 1. This
560 * is a special value that we use to trap recursive
561 * core dumps
562 */
umh_pipe_setup(struct subprocess_info * info,struct cred * new)563 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
564 {
565 struct file *files[2];
566 struct coredump_params *cp = (struct coredump_params *)info->data;
567 int err = create_pipe_files(files, 0);
568 if (err)
569 return err;
570
571 cp->file = files[1];
572
573 err = replace_fd(0, files[0], 0);
574 fput(files[0]);
575 /* and disallow core files too */
576 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
577
578 return err;
579 }
580
do_coredump(const kernel_siginfo_t * siginfo)581 void do_coredump(const kernel_siginfo_t *siginfo)
582 {
583 struct core_state core_state;
584 struct core_name cn;
585 struct mm_struct *mm = current->mm;
586 struct linux_binfmt * binfmt;
587 const struct cred *old_cred;
588 struct cred *cred;
589 int retval = 0;
590 int ispipe;
591 size_t *argv = NULL;
592 int argc = 0;
593 struct files_struct *displaced;
594 /* require nonrelative corefile path and be extra careful */
595 bool need_suid_safe = false;
596 bool core_dumped = false;
597 static atomic_t core_dump_count = ATOMIC_INIT(0);
598 struct coredump_params cprm = {
599 .siginfo = siginfo,
600 .regs = signal_pt_regs(),
601 .limit = rlimit(RLIMIT_CORE),
602 /*
603 * We must use the same mm->flags while dumping core to avoid
604 * inconsistency of bit flags, since this flag is not protected
605 * by any locks.
606 */
607 .mm_flags = mm->flags,
608 .vma_meta = NULL,
609 };
610
611 audit_core_dumps(siginfo->si_signo);
612
613 binfmt = mm->binfmt;
614 if (!binfmt || !binfmt->core_dump)
615 goto fail;
616 if (!__get_dumpable(cprm.mm_flags))
617 goto fail;
618
619 cred = prepare_creds();
620 if (!cred)
621 goto fail;
622 /*
623 * We cannot trust fsuid as being the "true" uid of the process
624 * nor do we know its entire history. We only know it was tainted
625 * so we dump it as root in mode 2, and only into a controlled
626 * environment (pipe handler or fully qualified path).
627 */
628 if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
629 /* Setuid core dump mode */
630 cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */
631 need_suid_safe = true;
632 }
633
634 retval = coredump_wait(siginfo->si_signo, &core_state);
635 if (retval < 0)
636 goto fail_creds;
637
638 old_cred = override_creds(cred);
639
640 ispipe = format_corename(&cn, &cprm, &argv, &argc);
641
642 if (ispipe) {
643 int argi;
644 int dump_count;
645 char **helper_argv;
646 struct subprocess_info *sub_info;
647
648 if (ispipe < 0) {
649 printk(KERN_WARNING "format_corename failed\n");
650 printk(KERN_WARNING "Aborting core\n");
651 goto fail_unlock;
652 }
653
654 if (cprm.limit == 1) {
655 /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
656 *
657 * Normally core limits are irrelevant to pipes, since
658 * we're not writing to the file system, but we use
659 * cprm.limit of 1 here as a special value, this is a
660 * consistent way to catch recursive crashes.
661 * We can still crash if the core_pattern binary sets
662 * RLIM_CORE = !1, but it runs as root, and can do
663 * lots of stupid things.
664 *
665 * Note that we use task_tgid_vnr here to grab the pid
666 * of the process group leader. That way we get the
667 * right pid if a thread in a multi-threaded
668 * core_pattern process dies.
669 */
670 printk(KERN_WARNING
671 "Process %d(%s) has RLIMIT_CORE set to 1\n",
672 task_tgid_vnr(current), current->comm);
673 printk(KERN_WARNING "Aborting core\n");
674 goto fail_unlock;
675 }
676 cprm.limit = RLIM_INFINITY;
677
678 dump_count = atomic_inc_return(&core_dump_count);
679 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
680 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
681 task_tgid_vnr(current), current->comm);
682 printk(KERN_WARNING "Skipping core dump\n");
683 goto fail_dropcount;
684 }
685
686 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
687 GFP_KERNEL);
688 if (!helper_argv) {
689 printk(KERN_WARNING "%s failed to allocate memory\n",
690 __func__);
691 goto fail_dropcount;
692 }
693 for (argi = 0; argi < argc; argi++)
694 helper_argv[argi] = cn.corename + argv[argi];
695 helper_argv[argi] = NULL;
696
697 retval = -ENOMEM;
698 sub_info = call_usermodehelper_setup(helper_argv[0],
699 helper_argv, NULL, GFP_KERNEL,
700 umh_pipe_setup, NULL, &cprm);
701 if (sub_info)
702 retval = call_usermodehelper_exec(sub_info,
703 UMH_WAIT_EXEC);
704
705 kfree(helper_argv);
706 if (retval) {
707 printk(KERN_INFO "Core dump to |%s pipe failed\n",
708 cn.corename);
709 goto close_fail;
710 }
711 } else {
712 struct inode *inode;
713 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
714 O_LARGEFILE | O_EXCL;
715
716 if (cprm.limit < binfmt->min_coredump)
717 goto fail_unlock;
718
719 if (need_suid_safe && cn.corename[0] != '/') {
720 printk(KERN_WARNING "Pid %d(%s) can only dump core "\
721 "to fully qualified path!\n",
722 task_tgid_vnr(current), current->comm);
723 printk(KERN_WARNING "Skipping core dump\n");
724 goto fail_unlock;
725 }
726
727 /*
728 * Unlink the file if it exists unless this is a SUID
729 * binary - in that case, we're running around with root
730 * privs and don't want to unlink another user's coredump.
731 */
732 if (!need_suid_safe) {
733 /*
734 * If it doesn't exist, that's fine. If there's some
735 * other problem, we'll catch it at the filp_open().
736 */
737 do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
738 }
739
740 /*
741 * There is a race between unlinking and creating the
742 * file, but if that causes an EEXIST here, that's
743 * fine - another process raced with us while creating
744 * the corefile, and the other process won. To userspace,
745 * what matters is that at least one of the two processes
746 * writes its coredump successfully, not which one.
747 */
748 if (need_suid_safe) {
749 /*
750 * Using user namespaces, normal user tasks can change
751 * their current->fs->root to point to arbitrary
752 * directories. Since the intention of the "only dump
753 * with a fully qualified path" rule is to control where
754 * coredumps may be placed using root privileges,
755 * current->fs->root must not be used. Instead, use the
756 * root directory of init_task.
757 */
758 struct path root;
759
760 task_lock(&init_task);
761 get_fs_root(init_task.fs, &root);
762 task_unlock(&init_task);
763 cprm.file = file_open_root(&root, cn.corename,
764 open_flags, 0600);
765 path_put(&root);
766 } else {
767 cprm.file = filp_open(cn.corename, open_flags, 0600);
768 }
769 if (IS_ERR(cprm.file))
770 goto fail_unlock;
771
772 inode = file_inode(cprm.file);
773 if (inode->i_nlink > 1)
774 goto close_fail;
775 if (d_unhashed(cprm.file->f_path.dentry))
776 goto close_fail;
777 /*
778 * AK: actually i see no reason to not allow this for named
779 * pipes etc, but keep the previous behaviour for now.
780 */
781 if (!S_ISREG(inode->i_mode))
782 goto close_fail;
783 /*
784 * Don't dump core if the filesystem changed owner or mode
785 * of the file during file creation. This is an issue when
786 * a process dumps core while its cwd is e.g. on a vfat
787 * filesystem.
788 */
789 if (!uid_eq(inode->i_uid, current_fsuid()))
790 goto close_fail;
791 if ((inode->i_mode & 0677) != 0600)
792 goto close_fail;
793 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
794 goto close_fail;
795 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
796 goto close_fail;
797 }
798
799 /* get us an unshared descriptor table; almost always a no-op */
800 retval = unshare_files(&displaced);
801 if (retval)
802 goto close_fail;
803 if (displaced)
804 put_files_struct(displaced);
805 if (!dump_interrupted()) {
806 /*
807 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
808 * have this set to NULL.
809 */
810 if (!cprm.file) {
811 pr_info("Core dump to |%s disabled\n", cn.corename);
812 goto close_fail;
813 }
814 if (!dump_vma_snapshot(&cprm))
815 goto close_fail;
816
817 file_start_write(cprm.file);
818 core_dumped = binfmt->core_dump(&cprm);
819 file_end_write(cprm.file);
820 free_vma_snapshot(&cprm);
821 }
822 if (ispipe && core_pipe_limit)
823 wait_for_dump_helpers(cprm.file);
824 close_fail:
825 if (cprm.file)
826 filp_close(cprm.file, NULL);
827 fail_dropcount:
828 if (ispipe)
829 atomic_dec(&core_dump_count);
830 fail_unlock:
831 kfree(argv);
832 kfree(cn.corename);
833 coredump_finish(mm, core_dumped);
834 revert_creds(old_cred);
835 fail_creds:
836 put_cred(cred);
837 fail:
838 return;
839 }
840
841 /*
842 * Core dumping helper functions. These are the only things you should
843 * do on a core-file: use only these functions to write out all the
844 * necessary info.
845 */
dump_emit(struct coredump_params * cprm,const void * addr,int nr)846 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
847 {
848 struct file *file = cprm->file;
849 loff_t pos = file->f_pos;
850 ssize_t n;
851 if (cprm->written + nr > cprm->limit)
852 return 0;
853
854
855 if (dump_interrupted())
856 return 0;
857 n = __kernel_write(file, addr, nr, &pos);
858 if (n != nr)
859 return 0;
860 file->f_pos = pos;
861 cprm->written += n;
862 cprm->pos += n;
863
864 return 1;
865 }
866 EXPORT_SYMBOL(dump_emit);
867
dump_skip(struct coredump_params * cprm,size_t nr)868 int dump_skip(struct coredump_params *cprm, size_t nr)
869 {
870 static char zeroes[PAGE_SIZE];
871 struct file *file = cprm->file;
872 if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
873 if (dump_interrupted() ||
874 file->f_op->llseek(file, nr, SEEK_CUR) < 0)
875 return 0;
876 cprm->pos += nr;
877 return 1;
878 } else {
879 while (nr > PAGE_SIZE) {
880 if (!dump_emit(cprm, zeroes, PAGE_SIZE))
881 return 0;
882 nr -= PAGE_SIZE;
883 }
884 return dump_emit(cprm, zeroes, nr);
885 }
886 }
887 EXPORT_SYMBOL(dump_skip);
888
889 #ifdef CONFIG_ELF_CORE
dump_user_range(struct coredump_params * cprm,unsigned long start,unsigned long len)890 int dump_user_range(struct coredump_params *cprm, unsigned long start,
891 unsigned long len)
892 {
893 unsigned long addr;
894
895 for (addr = start; addr < start + len; addr += PAGE_SIZE) {
896 struct page *page;
897 int stop;
898
899 /*
900 * To avoid having to allocate page tables for virtual address
901 * ranges that have never been used yet, and also to make it
902 * easy to generate sparse core files, use a helper that returns
903 * NULL when encountering an empty page table entry that would
904 * otherwise have been filled with the zero page.
905 */
906 page = get_dump_page(addr);
907 if (page) {
908 void *kaddr = kmap(page);
909
910 stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
911 kunmap(page);
912 put_page(page);
913 } else {
914 stop = !dump_skip(cprm, PAGE_SIZE);
915 }
916 if (stop)
917 return 0;
918 }
919 return 1;
920 }
921 #endif
922
dump_align(struct coredump_params * cprm,int align)923 int dump_align(struct coredump_params *cprm, int align)
924 {
925 unsigned mod = cprm->pos & (align - 1);
926 if (align & (align - 1))
927 return 0;
928 return mod ? dump_skip(cprm, align - mod) : 1;
929 }
930 EXPORT_SYMBOL(dump_align);
931
932 /*
933 * Ensures that file size is big enough to contain the current file
934 * postion. This prevents gdb from complaining about a truncated file
935 * if the last "write" to the file was dump_skip.
936 */
dump_truncate(struct coredump_params * cprm)937 void dump_truncate(struct coredump_params *cprm)
938 {
939 struct file *file = cprm->file;
940 loff_t offset;
941
942 if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
943 offset = file->f_op->llseek(file, 0, SEEK_CUR);
944 if (i_size_read(file->f_mapping->host) < offset)
945 do_truncate(file->f_path.dentry, offset, 0, file);
946 }
947 }
948 EXPORT_SYMBOL(dump_truncate);
949
950 /*
951 * The purpose of always_dump_vma() is to make sure that special kernel mappings
952 * that are useful for post-mortem analysis are included in every core dump.
953 * In that way we ensure that the core dump is fully interpretable later
954 * without matching up the same kernel and hardware config to see what PC values
955 * meant. These special mappings include - vDSO, vsyscall, and other
956 * architecture specific mappings
957 */
always_dump_vma(struct vm_area_struct * vma)958 static bool always_dump_vma(struct vm_area_struct *vma)
959 {
960 /* Any vsyscall mappings? */
961 if (vma == get_gate_vma(vma->vm_mm))
962 return true;
963
964 /*
965 * Assume that all vmas with a .name op should always be dumped.
966 * If this changes, a new vm_ops field can easily be added.
967 */
968 if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
969 return true;
970
971 /*
972 * arch_vma_name() returns non-NULL for special architecture mappings,
973 * such as vDSO sections.
974 */
975 if (arch_vma_name(vma))
976 return true;
977
978 return false;
979 }
980
981 #define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1
982
983 /*
984 * Decide how much of @vma's contents should be included in a core dump.
985 */
vma_dump_size(struct vm_area_struct * vma,unsigned long mm_flags)986 static unsigned long vma_dump_size(struct vm_area_struct *vma,
987 unsigned long mm_flags)
988 {
989 #define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
990
991 /* always dump the vdso and vsyscall sections */
992 if (always_dump_vma(vma))
993 goto whole;
994
995 if (vma->vm_flags & VM_DONTDUMP)
996 return 0;
997
998 /* support for DAX */
999 if (vma_is_dax(vma)) {
1000 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1001 goto whole;
1002 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1003 goto whole;
1004 return 0;
1005 }
1006
1007 /* Hugetlb memory check */
1008 if (is_vm_hugetlb_page(vma)) {
1009 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1010 goto whole;
1011 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1012 goto whole;
1013 return 0;
1014 }
1015
1016 /* Do not dump I/O mapped devices or special mappings */
1017 if (vma->vm_flags & VM_IO)
1018 return 0;
1019
1020 /* By default, dump shared memory if mapped from an anonymous file. */
1021 if (vma->vm_flags & VM_SHARED) {
1022 if (file_inode(vma->vm_file)->i_nlink == 0 ?
1023 FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1024 goto whole;
1025 return 0;
1026 }
1027
1028 /* Dump segments that have been written to. */
1029 if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1030 goto whole;
1031 if (vma->vm_file == NULL)
1032 return 0;
1033
1034 if (FILTER(MAPPED_PRIVATE))
1035 goto whole;
1036
1037 /*
1038 * If this is the beginning of an executable file mapping,
1039 * dump the first page to aid in determining what was mapped here.
1040 */
1041 if (FILTER(ELF_HEADERS) &&
1042 vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
1043 if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1044 return PAGE_SIZE;
1045
1046 /*
1047 * ELF libraries aren't always executable.
1048 * We'll want to check whether the mapping starts with the ELF
1049 * magic, but not now - we're holding the mmap lock,
1050 * so copy_from_user() doesn't work here.
1051 * Use a placeholder instead, and fix it up later in
1052 * dump_vma_snapshot().
1053 */
1054 return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
1055 }
1056
1057 #undef FILTER
1058
1059 return 0;
1060
1061 whole:
1062 return vma->vm_end - vma->vm_start;
1063 }
1064
first_vma(struct task_struct * tsk,struct vm_area_struct * gate_vma)1065 static struct vm_area_struct *first_vma(struct task_struct *tsk,
1066 struct vm_area_struct *gate_vma)
1067 {
1068 struct vm_area_struct *ret = tsk->mm->mmap;
1069
1070 if (ret)
1071 return ret;
1072 return gate_vma;
1073 }
1074
1075 /*
1076 * Helper function for iterating across a vma list. It ensures that the caller
1077 * will visit `gate_vma' prior to terminating the search.
1078 */
next_vma(struct vm_area_struct * this_vma,struct vm_area_struct * gate_vma)1079 static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
1080 struct vm_area_struct *gate_vma)
1081 {
1082 struct vm_area_struct *ret;
1083
1084 ret = this_vma->vm_next;
1085 if (ret)
1086 return ret;
1087 if (this_vma == gate_vma)
1088 return NULL;
1089 return gate_vma;
1090 }
1091
free_vma_snapshot(struct coredump_params * cprm)1092 static void free_vma_snapshot(struct coredump_params *cprm)
1093 {
1094 if (cprm->vma_meta) {
1095 int i;
1096 for (i = 0; i < cprm->vma_count; i++) {
1097 struct file *file = cprm->vma_meta[i].file;
1098 if (file)
1099 fput(file);
1100 }
1101 kvfree(cprm->vma_meta);
1102 cprm->vma_meta = NULL;
1103 }
1104 }
1105
1106 /*
1107 * Under the mmap_lock, take a snapshot of relevant information about the task's
1108 * VMAs.
1109 */
dump_vma_snapshot(struct coredump_params * cprm)1110 static bool dump_vma_snapshot(struct coredump_params *cprm)
1111 {
1112 struct vm_area_struct *vma, *gate_vma;
1113 struct mm_struct *mm = current->mm;
1114 int i;
1115
1116 /*
1117 * Once the stack expansion code is fixed to not change VMA bounds
1118 * under mmap_lock in read mode, this can be changed to take the
1119 * mmap_lock in read mode.
1120 */
1121 if (mmap_write_lock_killable(mm))
1122 return false;
1123
1124 cprm->vma_data_size = 0;
1125 gate_vma = get_gate_vma(mm);
1126 cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
1127
1128 cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
1129 if (!cprm->vma_meta) {
1130 mmap_write_unlock(mm);
1131 return false;
1132 }
1133
1134 for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
1135 vma = next_vma(vma, gate_vma), i++) {
1136 struct core_vma_metadata *m = cprm->vma_meta + i;
1137
1138 m->start = vma->vm_start;
1139 m->end = vma->vm_end;
1140 m->flags = vma->vm_flags;
1141 m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1142 m->pgoff = vma->vm_pgoff;
1143
1144 m->file = vma->vm_file;
1145 if (m->file)
1146 get_file(m->file);
1147 }
1148
1149 mmap_write_unlock(mm);
1150
1151 for (i = 0; i < cprm->vma_count; i++) {
1152 struct core_vma_metadata *m = cprm->vma_meta + i;
1153
1154 if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
1155 char elfmag[SELFMAG];
1156
1157 if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
1158 memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
1159 m->dump_size = 0;
1160 } else {
1161 m->dump_size = PAGE_SIZE;
1162 }
1163 }
1164
1165 cprm->vma_data_size += m->dump_size;
1166 }
1167
1168 return true;
1169 }
1170