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,bool name_only)156 static 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
185 free_buf:
186 kfree(pathbuf);
187 put_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 */
format_corename(struct core_name * cn,struct coredump_params * cprm,size_t ** argv,int * argc)196 static 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 if (cn->used != 0)
233 was_space = true;
234 pat_ptr++;
235 continue;
236 } else if (was_space) {
237 was_space = false;
238 err = cn_printf(cn, "%c", '\0');
239 if (err)
240 return err;
241 (*argv)[(*argc)++] = cn->used;
242 }
243 }
244 if (*pat_ptr != '%') {
245 err = cn_printf(cn, "%c", *pat_ptr++);
246 } else {
247 switch (*++pat_ptr) {
248 /* single % at the end, drop that */
249 case 0:
250 goto out;
251 /* Double percent, output one percent */
252 case '%':
253 err = cn_printf(cn, "%c", '%');
254 break;
255 /* pid */
256 case 'p':
257 pid_in_pattern = 1;
258 err = cn_printf(cn, "%d",
259 task_tgid_vnr(current));
260 break;
261 /* global pid */
262 case 'P':
263 err = cn_printf(cn, "%d",
264 task_tgid_nr(current));
265 break;
266 case 'i':
267 err = cn_printf(cn, "%d",
268 task_pid_vnr(current));
269 break;
270 case 'I':
271 err = cn_printf(cn, "%d",
272 task_pid_nr(current));
273 break;
274 /* uid */
275 case 'u':
276 err = cn_printf(cn, "%u",
277 from_kuid(&init_user_ns,
278 cred->uid));
279 break;
280 /* gid */
281 case 'g':
282 err = cn_printf(cn, "%u",
283 from_kgid(&init_user_ns,
284 cred->gid));
285 break;
286 case 'd':
287 err = cn_printf(cn, "%d",
288 __get_dumpable(cprm->mm_flags));
289 break;
290 /* signal that caused the coredump */
291 case 's':
292 err = cn_printf(cn, "%d",
293 cprm->siginfo->si_signo);
294 break;
295 /* UNIX time of coredump */
296 case 't': {
297 time64_t time;
298
299 time = ktime_get_real_seconds();
300 err = cn_printf(cn, "%lld", time);
301 break;
302 }
303 /* hostname */
304 case 'h':
305 down_read(&uts_sem);
306 err = cn_esc_printf(cn, "%s",
307 utsname()->nodename);
308 up_read(&uts_sem);
309 break;
310 /* executable, could be changed by prctl PR_SET_NAME etc */
311 case 'e':
312 err = cn_esc_printf(cn, "%s", current->comm);
313 break;
314 /* file name of executable */
315 case 'f':
316 err = cn_print_exe_file(cn, true);
317 break;
318 case 'E':
319 err = cn_print_exe_file(cn, false);
320 break;
321 /* core limit size */
322 case 'c':
323 err = cn_printf(cn, "%lu",
324 rlimit(RLIMIT_CORE));
325 break;
326 default:
327 break;
328 }
329 ++pat_ptr;
330 }
331
332 if (err)
333 return err;
334 }
335
336 out:
337 /* Backward compatibility with core_uses_pid:
338 *
339 * If core_pattern does not include a %p (as is the default)
340 * and core_uses_pid is set, then .%pid will be appended to
341 * the filename. Do not do this for piped commands. */
342 if (!ispipe && !pid_in_pattern && core_uses_pid) {
343 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
344 if (err)
345 return err;
346 }
347 return ispipe;
348 }
349
zap_process(struct task_struct * start,int exit_code,int flags)350 static int zap_process(struct task_struct *start, int exit_code, int flags)
351 {
352 struct task_struct *t;
353 int nr = 0;
354
355 /* ignore all signals except SIGKILL, see prepare_signal() */
356 start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
357 start->signal->group_exit_code = exit_code;
358 start->signal->group_stop_count = 0;
359
360 for_each_thread(start, t) {
361 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
362 if (t != current && t->mm) {
363 sigaddset(&t->pending.signal, SIGKILL);
364 signal_wake_up(t, 1);
365 nr++;
366 }
367 }
368
369 return nr;
370 }
371
zap_threads(struct task_struct * tsk,struct mm_struct * mm,struct core_state * core_state,int exit_code)372 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
373 struct core_state *core_state, int exit_code)
374 {
375 struct task_struct *g, *p;
376 unsigned long flags;
377 int nr = -EAGAIN;
378
379 spin_lock_irq(&tsk->sighand->siglock);
380 if (!signal_group_exit(tsk->signal)) {
381 mm->core_state = core_state;
382 tsk->signal->group_exit_task = tsk;
383 nr = zap_process(tsk, exit_code, 0);
384 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
385 }
386 spin_unlock_irq(&tsk->sighand->siglock);
387 if (unlikely(nr < 0))
388 return nr;
389
390 tsk->flags |= PF_DUMPCORE;
391 if (atomic_read(&mm->mm_users) == nr + 1)
392 goto done;
393 /*
394 * We should find and kill all tasks which use this mm, and we should
395 * count them correctly into ->nr_threads. We don't take tasklist
396 * lock, but this is safe wrt:
397 *
398 * fork:
399 * None of sub-threads can fork after zap_process(leader). All
400 * processes which were created before this point should be
401 * visible to zap_threads() because copy_process() adds the new
402 * process to the tail of init_task.tasks list, and lock/unlock
403 * of ->siglock provides a memory barrier.
404 *
405 * do_exit:
406 * The caller holds mm->mmap_lock. This means that the task which
407 * uses this mm can't pass exit_mm(), so it can't exit or clear
408 * its ->mm.
409 *
410 * de_thread:
411 * It does list_replace_rcu(&leader->tasks, ¤t->tasks),
412 * we must see either old or new leader, this does not matter.
413 * However, it can change p->sighand, so lock_task_sighand(p)
414 * must be used. Since p->mm != NULL and we hold ->mmap_lock
415 * it can't fail.
416 *
417 * Note also that "g" can be the old leader with ->mm == NULL
418 * and already unhashed and thus removed from ->thread_group.
419 * This is OK, __unhash_process()->list_del_rcu() does not
420 * clear the ->next pointer, we will find the new leader via
421 * next_thread().
422 */
423 rcu_read_lock();
424 for_each_process(g) {
425 if (g == tsk->group_leader)
426 continue;
427 if (g->flags & PF_KTHREAD)
428 continue;
429
430 for_each_thread(g, p) {
431 if (unlikely(!p->mm))
432 continue;
433 if (unlikely(p->mm == mm)) {
434 lock_task_sighand(p, &flags);
435 nr += zap_process(p, exit_code,
436 SIGNAL_GROUP_EXIT);
437 unlock_task_sighand(p, &flags);
438 }
439 break;
440 }
441 }
442 rcu_read_unlock();
443 done:
444 atomic_set(&core_state->nr_threads, nr);
445 return nr;
446 }
447
coredump_wait(int exit_code,struct core_state * core_state)448 static int coredump_wait(int exit_code, struct core_state *core_state)
449 {
450 struct task_struct *tsk = current;
451 struct mm_struct *mm = tsk->mm;
452 int core_waiters = -EBUSY;
453
454 init_completion(&core_state->startup);
455 core_state->dumper.task = tsk;
456 core_state->dumper.next = NULL;
457
458 if (mmap_write_lock_killable(mm))
459 return -EINTR;
460
461 if (!mm->core_state)
462 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
463 mmap_write_unlock(mm);
464
465 if (core_waiters > 0) {
466 struct core_thread *ptr;
467
468 freezer_do_not_count();
469 wait_for_completion(&core_state->startup);
470 freezer_count();
471 /*
472 * Wait for all the threads to become inactive, so that
473 * all the thread context (extended register state, like
474 * fpu etc) gets copied to the memory.
475 */
476 ptr = core_state->dumper.next;
477 while (ptr != NULL) {
478 wait_task_inactive(ptr->task, 0);
479 ptr = ptr->next;
480 }
481 }
482
483 return core_waiters;
484 }
485
coredump_finish(struct mm_struct * mm,bool core_dumped)486 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
487 {
488 struct core_thread *curr, *next;
489 struct task_struct *task;
490
491 spin_lock_irq(¤t->sighand->siglock);
492 if (core_dumped && !__fatal_signal_pending(current))
493 current->signal->group_exit_code |= 0x80;
494 current->signal->group_exit_task = NULL;
495 current->signal->flags = SIGNAL_GROUP_EXIT;
496 spin_unlock_irq(¤t->sighand->siglock);
497
498 next = mm->core_state->dumper.next;
499 while ((curr = next) != NULL) {
500 next = curr->next;
501 task = curr->task;
502 /*
503 * see exit_mm(), curr->task must not see
504 * ->task == NULL before we read ->next.
505 */
506 smp_mb();
507 curr->task = NULL;
508 wake_up_process(task);
509 }
510
511 mm->core_state = NULL;
512 }
513
dump_interrupted(void)514 static bool dump_interrupted(void)
515 {
516 /*
517 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
518 * can do try_to_freeze() and check __fatal_signal_pending(),
519 * but then we need to teach dump_write() to restart and clear
520 * TIF_SIGPENDING.
521 */
522 return fatal_signal_pending(current) || freezing(current);
523 }
524
wait_for_dump_helpers(struct file * file)525 static void wait_for_dump_helpers(struct file *file)
526 {
527 struct pipe_inode_info *pipe = file->private_data;
528
529 pipe_lock(pipe);
530 pipe->readers++;
531 pipe->writers--;
532 wake_up_interruptible_sync(&pipe->rd_wait);
533 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
534 pipe_unlock(pipe);
535
536 /*
537 * We actually want wait_event_freezable() but then we need
538 * to clear TIF_SIGPENDING and improve dump_interrupted().
539 */
540 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
541
542 pipe_lock(pipe);
543 pipe->readers--;
544 pipe->writers++;
545 pipe_unlock(pipe);
546 }
547
548 /*
549 * umh_pipe_setup
550 * helper function to customize the process used
551 * to collect the core in userspace. Specifically
552 * it sets up a pipe and installs it as fd 0 (stdin)
553 * for the process. Returns 0 on success, or
554 * PTR_ERR on failure.
555 * Note that it also sets the core limit to 1. This
556 * is a special value that we use to trap recursive
557 * core dumps
558 */
umh_pipe_setup(struct subprocess_info * info,struct cred * new)559 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
560 {
561 struct file *files[2];
562 struct coredump_params *cp = (struct coredump_params *)info->data;
563 int err = create_pipe_files(files, 0);
564 if (err)
565 return err;
566
567 cp->file = files[1];
568
569 err = replace_fd(0, files[0], 0);
570 fput(files[0]);
571 /* and disallow core files too */
572 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
573
574 return err;
575 }
576
do_coredump(const kernel_siginfo_t * siginfo)577 void do_coredump(const kernel_siginfo_t *siginfo)
578 {
579 struct core_state core_state;
580 struct core_name cn;
581 struct mm_struct *mm = current->mm;
582 struct linux_binfmt * binfmt;
583 const struct cred *old_cred;
584 struct cred *cred;
585 int retval = 0;
586 int ispipe;
587 size_t *argv = NULL;
588 int argc = 0;
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 user_namespace *mnt_userns;
707 struct inode *inode;
708 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
709 O_LARGEFILE | O_EXCL;
710
711 if (cprm.limit < binfmt->min_coredump)
712 goto fail_unlock;
713
714 if (need_suid_safe && cn.corename[0] != '/') {
715 printk(KERN_WARNING "Pid %d(%s) can only dump core "\
716 "to fully qualified path!\n",
717 task_tgid_vnr(current), current->comm);
718 printk(KERN_WARNING "Skipping core dump\n");
719 goto fail_unlock;
720 }
721
722 /*
723 * Unlink the file if it exists unless this is a SUID
724 * binary - in that case, we're running around with root
725 * privs and don't want to unlink another user's coredump.
726 */
727 if (!need_suid_safe) {
728 /*
729 * If it doesn't exist, that's fine. If there's some
730 * other problem, we'll catch it at the filp_open().
731 */
732 do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
733 }
734
735 /*
736 * There is a race between unlinking and creating the
737 * file, but if that causes an EEXIST here, that's
738 * fine - another process raced with us while creating
739 * the corefile, and the other process won. To userspace,
740 * what matters is that at least one of the two processes
741 * writes its coredump successfully, not which one.
742 */
743 if (need_suid_safe) {
744 /*
745 * Using user namespaces, normal user tasks can change
746 * their current->fs->root to point to arbitrary
747 * directories. Since the intention of the "only dump
748 * with a fully qualified path" rule is to control where
749 * coredumps may be placed using root privileges,
750 * current->fs->root must not be used. Instead, use the
751 * root directory of init_task.
752 */
753 struct path root;
754
755 task_lock(&init_task);
756 get_fs_root(init_task.fs, &root);
757 task_unlock(&init_task);
758 cprm.file = file_open_root(&root, cn.corename,
759 open_flags, 0600);
760 path_put(&root);
761 } else {
762 cprm.file = filp_open(cn.corename, open_flags, 0600);
763 }
764 if (IS_ERR(cprm.file))
765 goto fail_unlock;
766
767 inode = file_inode(cprm.file);
768 if (inode->i_nlink > 1)
769 goto close_fail;
770 if (d_unhashed(cprm.file->f_path.dentry))
771 goto close_fail;
772 /*
773 * AK: actually i see no reason to not allow this for named
774 * pipes etc, but keep the previous behaviour for now.
775 */
776 if (!S_ISREG(inode->i_mode))
777 goto close_fail;
778 /*
779 * Don't dump core if the filesystem changed owner or mode
780 * of the file during file creation. This is an issue when
781 * a process dumps core while its cwd is e.g. on a vfat
782 * filesystem.
783 */
784 mnt_userns = file_mnt_user_ns(cprm.file);
785 if (!uid_eq(i_uid_into_mnt(mnt_userns, inode),
786 current_fsuid())) {
787 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n",
788 cn.corename);
789 goto close_fail;
790 }
791 if ((inode->i_mode & 0677) != 0600) {
792 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n",
793 cn.corename);
794 goto close_fail;
795 }
796 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
797 goto close_fail;
798 if (do_truncate(mnt_userns, cprm.file->f_path.dentry,
799 0, 0, cprm.file))
800 goto close_fail;
801 }
802
803 /* get us an unshared descriptor table; almost always a no-op */
804 /* The cell spufs coredump code reads the file descriptor tables */
805 retval = unshare_files();
806 if (retval)
807 goto close_fail;
808 if (!dump_interrupted()) {
809 /*
810 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
811 * have this set to NULL.
812 */
813 if (!cprm.file) {
814 pr_info("Core dump to |%s disabled\n", cn.corename);
815 goto close_fail;
816 }
817 file_start_write(cprm.file);
818 core_dumped = binfmt->core_dump(&cprm);
819 /*
820 * Ensures that file size is big enough to contain the current
821 * file postion. This prevents gdb from complaining about
822 * a truncated file if the last "write" to the file was
823 * dump_skip.
824 */
825 if (cprm.to_skip) {
826 cprm.to_skip--;
827 dump_emit(&cprm, "", 1);
828 }
829 file_end_write(cprm.file);
830 }
831 if (ispipe && core_pipe_limit)
832 wait_for_dump_helpers(cprm.file);
833 close_fail:
834 if (cprm.file)
835 filp_close(cprm.file, NULL);
836 fail_dropcount:
837 if (ispipe)
838 atomic_dec(&core_dump_count);
839 fail_unlock:
840 kfree(argv);
841 kfree(cn.corename);
842 coredump_finish(mm, core_dumped);
843 revert_creds(old_cred);
844 fail_creds:
845 put_cred(cred);
846 fail:
847 return;
848 }
849
850 /*
851 * Core dumping helper functions. These are the only things you should
852 * do on a core-file: use only these functions to write out all the
853 * necessary info.
854 */
__dump_emit(struct coredump_params * cprm,const void * addr,int nr)855 static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
856 {
857 struct file *file = cprm->file;
858 loff_t pos = file->f_pos;
859 ssize_t n;
860 if (cprm->written + nr > cprm->limit)
861 return 0;
862
863
864 if (dump_interrupted())
865 return 0;
866 n = __kernel_write(file, addr, nr, &pos);
867 if (n != nr)
868 return 0;
869 file->f_pos = pos;
870 cprm->written += n;
871 cprm->pos += n;
872
873 return 1;
874 }
875
__dump_skip(struct coredump_params * cprm,size_t nr)876 static int __dump_skip(struct coredump_params *cprm, size_t nr)
877 {
878 static char zeroes[PAGE_SIZE];
879 struct file *file = cprm->file;
880 if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
881 if (dump_interrupted() ||
882 file->f_op->llseek(file, nr, SEEK_CUR) < 0)
883 return 0;
884 cprm->pos += nr;
885 return 1;
886 } else {
887 while (nr > PAGE_SIZE) {
888 if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
889 return 0;
890 nr -= PAGE_SIZE;
891 }
892 return __dump_emit(cprm, zeroes, nr);
893 }
894 }
895
dump_emit(struct coredump_params * cprm,const void * addr,int nr)896 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
897 {
898 if (cprm->to_skip) {
899 if (!__dump_skip(cprm, cprm->to_skip))
900 return 0;
901 cprm->to_skip = 0;
902 }
903 return __dump_emit(cprm, addr, nr);
904 }
905 EXPORT_SYMBOL(dump_emit);
906
dump_skip_to(struct coredump_params * cprm,unsigned long pos)907 void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
908 {
909 cprm->to_skip = pos - cprm->pos;
910 }
911 EXPORT_SYMBOL(dump_skip_to);
912
dump_skip(struct coredump_params * cprm,size_t nr)913 void dump_skip(struct coredump_params *cprm, size_t nr)
914 {
915 cprm->to_skip += nr;
916 }
917 EXPORT_SYMBOL(dump_skip);
918
919 #ifdef CONFIG_ELF_CORE
dump_user_range(struct coredump_params * cprm,unsigned long start,unsigned long len)920 int dump_user_range(struct coredump_params *cprm, unsigned long start,
921 unsigned long len)
922 {
923 unsigned long addr;
924
925 for (addr = start; addr < start + len; addr += PAGE_SIZE) {
926 struct page *page;
927 int stop;
928
929 /*
930 * To avoid having to allocate page tables for virtual address
931 * ranges that have never been used yet, and also to make it
932 * easy to generate sparse core files, use a helper that returns
933 * NULL when encountering an empty page table entry that would
934 * otherwise have been filled with the zero page.
935 */
936 page = get_dump_page(addr);
937 if (page) {
938 void *kaddr = kmap_local_page(page);
939
940 stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
941 kunmap_local(kaddr);
942 put_page(page);
943 if (stop)
944 return 0;
945 } else {
946 dump_skip(cprm, PAGE_SIZE);
947 }
948 }
949 return 1;
950 }
951 #endif
952
dump_align(struct coredump_params * cprm,int align)953 int dump_align(struct coredump_params *cprm, int align)
954 {
955 unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
956 if (align & (align - 1))
957 return 0;
958 if (mod)
959 cprm->to_skip += align - mod;
960 return 1;
961 }
962 EXPORT_SYMBOL(dump_align);
963
964 /*
965 * The purpose of always_dump_vma() is to make sure that special kernel mappings
966 * that are useful for post-mortem analysis are included in every core dump.
967 * In that way we ensure that the core dump is fully interpretable later
968 * without matching up the same kernel and hardware config to see what PC values
969 * meant. These special mappings include - vDSO, vsyscall, and other
970 * architecture specific mappings
971 */
always_dump_vma(struct vm_area_struct * vma)972 static bool always_dump_vma(struct vm_area_struct *vma)
973 {
974 /* Any vsyscall mappings? */
975 if (vma == get_gate_vma(vma->vm_mm))
976 return true;
977
978 /*
979 * Assume that all vmas with a .name op should always be dumped.
980 * If this changes, a new vm_ops field can easily be added.
981 */
982 if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
983 return true;
984
985 /*
986 * arch_vma_name() returns non-NULL for special architecture mappings,
987 * such as vDSO sections.
988 */
989 if (arch_vma_name(vma))
990 return true;
991
992 return false;
993 }
994
995 /*
996 * Decide how much of @vma's contents should be included in a core dump.
997 */
vma_dump_size(struct vm_area_struct * vma,unsigned long mm_flags)998 static unsigned long vma_dump_size(struct vm_area_struct *vma,
999 unsigned long mm_flags)
1000 {
1001 #define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
1002
1003 /* always dump the vdso and vsyscall sections */
1004 if (always_dump_vma(vma))
1005 goto whole;
1006
1007 if (vma->vm_flags & VM_DONTDUMP)
1008 return 0;
1009
1010 /* support for DAX */
1011 if (vma_is_dax(vma)) {
1012 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1013 goto whole;
1014 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1015 goto whole;
1016 return 0;
1017 }
1018
1019 /* Hugetlb memory check */
1020 if (is_vm_hugetlb_page(vma)) {
1021 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1022 goto whole;
1023 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1024 goto whole;
1025 return 0;
1026 }
1027
1028 /* Do not dump I/O mapped devices or special mappings */
1029 if (vma->vm_flags & VM_IO)
1030 return 0;
1031
1032 /* By default, dump shared memory if mapped from an anonymous file. */
1033 if (vma->vm_flags & VM_SHARED) {
1034 if (file_inode(vma->vm_file)->i_nlink == 0 ?
1035 FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1036 goto whole;
1037 return 0;
1038 }
1039
1040 /* Dump segments that have been written to. */
1041 if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1042 goto whole;
1043 if (vma->vm_file == NULL)
1044 return 0;
1045
1046 if (FILTER(MAPPED_PRIVATE))
1047 goto whole;
1048
1049 /*
1050 * If this is the beginning of an executable file mapping,
1051 * dump the first page to aid in determining what was mapped here.
1052 */
1053 if (FILTER(ELF_HEADERS) &&
1054 vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ) &&
1055 (READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1056 return PAGE_SIZE;
1057
1058 #undef FILTER
1059
1060 return 0;
1061
1062 whole:
1063 return vma->vm_end - vma->vm_start;
1064 }
1065
first_vma(struct task_struct * tsk,struct vm_area_struct * gate_vma)1066 static struct vm_area_struct *first_vma(struct task_struct *tsk,
1067 struct vm_area_struct *gate_vma)
1068 {
1069 struct vm_area_struct *ret = tsk->mm->mmap;
1070
1071 if (ret)
1072 return ret;
1073 return gate_vma;
1074 }
1075
1076 /*
1077 * Helper function for iterating across a vma list. It ensures that the caller
1078 * will visit `gate_vma' prior to terminating the search.
1079 */
next_vma(struct vm_area_struct * this_vma,struct vm_area_struct * gate_vma)1080 static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
1081 struct vm_area_struct *gate_vma)
1082 {
1083 struct vm_area_struct *ret;
1084
1085 ret = this_vma->vm_next;
1086 if (ret)
1087 return ret;
1088 if (this_vma == gate_vma)
1089 return NULL;
1090 return gate_vma;
1091 }
1092
1093 /*
1094 * Under the mmap_lock, take a snapshot of relevant information about the task's
1095 * VMAs.
1096 */
dump_vma_snapshot(struct coredump_params * cprm,int * vma_count,struct core_vma_metadata ** vma_meta,size_t * vma_data_size_ptr)1097 int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
1098 struct core_vma_metadata **vma_meta,
1099 size_t *vma_data_size_ptr)
1100 {
1101 struct vm_area_struct *vma, *gate_vma;
1102 struct mm_struct *mm = current->mm;
1103 int i;
1104 size_t vma_data_size = 0;
1105
1106 /*
1107 * Once the stack expansion code is fixed to not change VMA bounds
1108 * under mmap_lock in read mode, this can be changed to take the
1109 * mmap_lock in read mode.
1110 */
1111 if (mmap_write_lock_killable(mm))
1112 return -EINTR;
1113
1114 gate_vma = get_gate_vma(mm);
1115 *vma_count = mm->map_count + (gate_vma ? 1 : 0);
1116
1117 *vma_meta = kvmalloc_array(*vma_count, sizeof(**vma_meta), GFP_KERNEL);
1118 if (!*vma_meta) {
1119 mmap_write_unlock(mm);
1120 return -ENOMEM;
1121 }
1122
1123 for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
1124 vma = next_vma(vma, gate_vma), i++) {
1125 struct core_vma_metadata *m = (*vma_meta) + i;
1126
1127 m->start = vma->vm_start;
1128 m->end = vma->vm_end;
1129 m->flags = vma->vm_flags;
1130 m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1131
1132 vma_data_size += m->dump_size;
1133 }
1134
1135 mmap_write_unlock(mm);
1136
1137 if (WARN_ON(i != *vma_count)) {
1138 kvfree(*vma_meta);
1139 return -EFAULT;
1140 }
1141
1142 *vma_data_size_ptr = vma_data_size;
1143 return 0;
1144 }
1145
