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/kmod.h>
35 #include <linux/fsnotify.h>
36 #include <linux/fs_struct.h>
37 #include <linux/pipe_fs_i.h>
38 #include <linux/oom.h>
39 #include <linux/compat.h>
40 #include <linux/fs.h>
41 #include <linux/path.h>
42 #include <linux/timekeeping.h>
43 #include <linux/sysctl.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 static int core_uses_pid;
60 static unsigned int core_pipe_limit;
61 static 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
expand_corename(struct core_name * cn,int size)69 static int expand_corename(struct core_name *cn, int size)
70 {
71 char *corename;
72
73 size = kmalloc_size_roundup(size);
74 corename = krealloc(cn->corename, size, GFP_KERNEL);
75
76 if (!corename)
77 return -ENOMEM;
78
79 if (size > core_name_size) /* racy but harmless */
80 core_name_size = size;
81
82 cn->size = size;
83 cn->corename = corename;
84 return 0;
85 }
86
cn_vprintf(struct core_name * cn,const char * fmt,va_list arg)87 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
88 va_list arg)
89 {
90 int free, need;
91 va_list arg_copy;
92
93 again:
94 free = cn->size - cn->used;
95
96 va_copy(arg_copy, arg);
97 need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
98 va_end(arg_copy);
99
100 if (need < free) {
101 cn->used += need;
102 return 0;
103 }
104
105 if (!expand_corename(cn, cn->size + need - free + 1))
106 goto again;
107
108 return -ENOMEM;
109 }
110
cn_printf(struct core_name * cn,const char * fmt,...)111 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
112 {
113 va_list arg;
114 int ret;
115
116 va_start(arg, fmt);
117 ret = cn_vprintf(cn, fmt, arg);
118 va_end(arg);
119
120 return ret;
121 }
122
123 static __printf(2, 3)
cn_esc_printf(struct core_name * cn,const char * fmt,...)124 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
125 {
126 int cur = cn->used;
127 va_list arg;
128 int ret;
129
130 va_start(arg, fmt);
131 ret = cn_vprintf(cn, fmt, arg);
132 va_end(arg);
133
134 if (ret == 0) {
135 /*
136 * Ensure that this coredump name component can't cause the
137 * resulting corefile path to consist of a ".." or ".".
138 */
139 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
140 (cn->used - cur == 2 && cn->corename[cur] == '.'
141 && cn->corename[cur+1] == '.'))
142 cn->corename[cur] = '!';
143
144 /*
145 * Empty names are fishy and could be used to create a "//" in a
146 * corefile name, causing the coredump to happen one directory
147 * level too high. Enforce that all components of the core
148 * pattern are at least one character long.
149 */
150 if (cn->used == cur)
151 ret = cn_printf(cn, "!");
152 }
153
154 for (; cur < cn->used; ++cur) {
155 if (cn->corename[cur] == '/')
156 cn->corename[cur] = '!';
157 }
158 return ret;
159 }
160
cn_print_exe_file(struct core_name * cn,bool name_only)161 static int cn_print_exe_file(struct core_name *cn, bool name_only)
162 {
163 struct file *exe_file;
164 char *pathbuf, *path, *ptr;
165 int ret;
166
167 exe_file = get_mm_exe_file(current->mm);
168 if (!exe_file)
169 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
170
171 pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
172 if (!pathbuf) {
173 ret = -ENOMEM;
174 goto put_exe_file;
175 }
176
177 path = file_path(exe_file, pathbuf, PATH_MAX);
178 if (IS_ERR(path)) {
179 ret = PTR_ERR(path);
180 goto free_buf;
181 }
182
183 if (name_only) {
184 ptr = strrchr(path, '/');
185 if (ptr)
186 path = ptr + 1;
187 }
188 ret = cn_esc_printf(cn, "%s", path);
189
190 free_buf:
191 kfree(pathbuf);
192 put_exe_file:
193 fput(exe_file);
194 return ret;
195 }
196
197 /* format_corename will inspect the pattern parameter, and output a
198 * name into corename, which must have space for at least
199 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
200 */
format_corename(struct core_name * cn,struct coredump_params * cprm,size_t ** argv,int * argc)201 static int format_corename(struct core_name *cn, struct coredump_params *cprm,
202 size_t **argv, int *argc)
203 {
204 const struct cred *cred = current_cred();
205 const char *pat_ptr = core_pattern;
206 int ispipe = (*pat_ptr == '|');
207 bool was_space = false;
208 int pid_in_pattern = 0;
209 int err = 0;
210
211 cn->used = 0;
212 cn->corename = NULL;
213 if (expand_corename(cn, core_name_size))
214 return -ENOMEM;
215 cn->corename[0] = '\0';
216
217 if (ispipe) {
218 int argvs = sizeof(core_pattern) / 2;
219 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
220 if (!(*argv))
221 return -ENOMEM;
222 (*argv)[(*argc)++] = 0;
223 ++pat_ptr;
224 if (!(*pat_ptr))
225 return -ENOMEM;
226 }
227
228 /* Repeat as long as we have more pattern to process and more output
229 space */
230 while (*pat_ptr) {
231 /*
232 * Split on spaces before doing template expansion so that
233 * %e and %E don't get split if they have spaces in them
234 */
235 if (ispipe) {
236 if (isspace(*pat_ptr)) {
237 if (cn->used != 0)
238 was_space = true;
239 pat_ptr++;
240 continue;
241 } else if (was_space) {
242 was_space = false;
243 err = cn_printf(cn, "%c", '\0');
244 if (err)
245 return err;
246 (*argv)[(*argc)++] = cn->used;
247 }
248 }
249 if (*pat_ptr != '%') {
250 err = cn_printf(cn, "%c", *pat_ptr++);
251 } else {
252 switch (*++pat_ptr) {
253 /* single % at the end, drop that */
254 case 0:
255 goto out;
256 /* Double percent, output one percent */
257 case '%':
258 err = cn_printf(cn, "%c", '%');
259 break;
260 /* pid */
261 case 'p':
262 pid_in_pattern = 1;
263 err = cn_printf(cn, "%d",
264 task_tgid_vnr(current));
265 break;
266 /* global pid */
267 case 'P':
268 err = cn_printf(cn, "%d",
269 task_tgid_nr(current));
270 break;
271 case 'i':
272 err = cn_printf(cn, "%d",
273 task_pid_vnr(current));
274 break;
275 case 'I':
276 err = cn_printf(cn, "%d",
277 task_pid_nr(current));
278 break;
279 /* uid */
280 case 'u':
281 err = cn_printf(cn, "%u",
282 from_kuid(&init_user_ns,
283 cred->uid));
284 break;
285 /* gid */
286 case 'g':
287 err = cn_printf(cn, "%u",
288 from_kgid(&init_user_ns,
289 cred->gid));
290 break;
291 case 'd':
292 err = cn_printf(cn, "%d",
293 __get_dumpable(cprm->mm_flags));
294 break;
295 /* signal that caused the coredump */
296 case 's':
297 err = cn_printf(cn, "%d",
298 cprm->siginfo->si_signo);
299 break;
300 /* UNIX time of coredump */
301 case 't': {
302 time64_t time;
303
304 time = ktime_get_real_seconds();
305 err = cn_printf(cn, "%lld", time);
306 break;
307 }
308 /* hostname */
309 case 'h':
310 down_read(&uts_sem);
311 err = cn_esc_printf(cn, "%s",
312 utsname()->nodename);
313 up_read(&uts_sem);
314 break;
315 /* executable, could be changed by prctl PR_SET_NAME etc */
316 case 'e':
317 err = cn_esc_printf(cn, "%s", current->comm);
318 break;
319 /* file name of executable */
320 case 'f':
321 err = cn_print_exe_file(cn, true);
322 break;
323 case 'E':
324 err = cn_print_exe_file(cn, false);
325 break;
326 /* core limit size */
327 case 'c':
328 err = cn_printf(cn, "%lu",
329 rlimit(RLIMIT_CORE));
330 break;
331 /* CPU the task ran on */
332 case 'C':
333 err = cn_printf(cn, "%d", cprm->cpu);
334 break;
335 default:
336 break;
337 }
338 ++pat_ptr;
339 }
340
341 if (err)
342 return err;
343 }
344
345 out:
346 /* Backward compatibility with core_uses_pid:
347 *
348 * If core_pattern does not include a %p (as is the default)
349 * and core_uses_pid is set, then .%pid will be appended to
350 * the filename. Do not do this for piped commands. */
351 if (!ispipe && !pid_in_pattern && core_uses_pid) {
352 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
353 if (err)
354 return err;
355 }
356 return ispipe;
357 }
358
zap_process(struct task_struct * start,int exit_code)359 static int zap_process(struct task_struct *start, int exit_code)
360 {
361 struct task_struct *t;
362 int nr = 0;
363
364 /* Allow SIGKILL, see prepare_signal() */
365 start->signal->flags = SIGNAL_GROUP_EXIT;
366 start->signal->group_exit_code = exit_code;
367 start->signal->group_stop_count = 0;
368
369 for_each_thread(start, t) {
370 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
371 if (t != current && !(t->flags & PF_POSTCOREDUMP)) {
372 sigaddset(&t->pending.signal, SIGKILL);
373 signal_wake_up(t, 1);
374 nr++;
375 }
376 }
377
378 return nr;
379 }
380
zap_threads(struct task_struct * tsk,struct core_state * core_state,int exit_code)381 static int zap_threads(struct task_struct *tsk,
382 struct core_state *core_state, int exit_code)
383 {
384 struct signal_struct *signal = tsk->signal;
385 int nr = -EAGAIN;
386
387 spin_lock_irq(&tsk->sighand->siglock);
388 if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) {
389 signal->core_state = core_state;
390 nr = zap_process(tsk, exit_code);
391 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
392 tsk->flags |= PF_DUMPCORE;
393 atomic_set(&core_state->nr_threads, nr);
394 }
395 spin_unlock_irq(&tsk->sighand->siglock);
396 return nr;
397 }
398
coredump_wait(int exit_code,struct core_state * core_state)399 static int coredump_wait(int exit_code, struct core_state *core_state)
400 {
401 struct task_struct *tsk = current;
402 int core_waiters = -EBUSY;
403
404 init_completion(&core_state->startup);
405 core_state->dumper.task = tsk;
406 core_state->dumper.next = NULL;
407
408 core_waiters = zap_threads(tsk, core_state, exit_code);
409 if (core_waiters > 0) {
410 struct core_thread *ptr;
411
412 wait_for_completion_state(&core_state->startup,
413 TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
414 /*
415 * Wait for all the threads to become inactive, so that
416 * all the thread context (extended register state, like
417 * fpu etc) gets copied to the memory.
418 */
419 ptr = core_state->dumper.next;
420 while (ptr != NULL) {
421 wait_task_inactive(ptr->task, TASK_ANY);
422 ptr = ptr->next;
423 }
424 }
425
426 return core_waiters;
427 }
428
coredump_finish(bool core_dumped)429 static void coredump_finish(bool core_dumped)
430 {
431 struct core_thread *curr, *next;
432 struct task_struct *task;
433
434 spin_lock_irq(¤t->sighand->siglock);
435 if (core_dumped && !__fatal_signal_pending(current))
436 current->signal->group_exit_code |= 0x80;
437 next = current->signal->core_state->dumper.next;
438 current->signal->core_state = NULL;
439 spin_unlock_irq(¤t->sighand->siglock);
440
441 while ((curr = next) != NULL) {
442 next = curr->next;
443 task = curr->task;
444 /*
445 * see coredump_task_exit(), curr->task must not see
446 * ->task == NULL before we read ->next.
447 */
448 smp_mb();
449 curr->task = NULL;
450 wake_up_process(task);
451 }
452 }
453
dump_interrupted(void)454 static bool dump_interrupted(void)
455 {
456 /*
457 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
458 * can do try_to_freeze() and check __fatal_signal_pending(),
459 * but then we need to teach dump_write() to restart and clear
460 * TIF_SIGPENDING.
461 */
462 return fatal_signal_pending(current) || freezing(current);
463 }
464
wait_for_dump_helpers(struct file * file)465 static void wait_for_dump_helpers(struct file *file)
466 {
467 struct pipe_inode_info *pipe = file->private_data;
468
469 pipe_lock(pipe);
470 pipe->readers++;
471 pipe->writers--;
472 wake_up_interruptible_sync(&pipe->rd_wait);
473 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
474 pipe_unlock(pipe);
475
476 /*
477 * We actually want wait_event_freezable() but then we need
478 * to clear TIF_SIGPENDING and improve dump_interrupted().
479 */
480 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
481
482 pipe_lock(pipe);
483 pipe->readers--;
484 pipe->writers++;
485 pipe_unlock(pipe);
486 }
487
488 /*
489 * umh_pipe_setup
490 * helper function to customize the process used
491 * to collect the core in userspace. Specifically
492 * it sets up a pipe and installs it as fd 0 (stdin)
493 * for the process. Returns 0 on success, or
494 * PTR_ERR on failure.
495 * Note that it also sets the core limit to 1. This
496 * is a special value that we use to trap recursive
497 * core dumps
498 */
umh_pipe_setup(struct subprocess_info * info,struct cred * new)499 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
500 {
501 struct file *files[2];
502 struct coredump_params *cp = (struct coredump_params *)info->data;
503 int err = create_pipe_files(files, 0);
504 if (err)
505 return err;
506
507 cp->file = files[1];
508
509 err = replace_fd(0, files[0], 0);
510 fput(files[0]);
511 /* and disallow core files too */
512 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
513
514 return err;
515 }
516
do_coredump(const kernel_siginfo_t * siginfo)517 void do_coredump(const kernel_siginfo_t *siginfo)
518 {
519 struct core_state core_state;
520 struct core_name cn;
521 struct mm_struct *mm = current->mm;
522 struct linux_binfmt * binfmt;
523 const struct cred *old_cred;
524 struct cred *cred;
525 int retval = 0;
526 int ispipe;
527 size_t *argv = NULL;
528 int argc = 0;
529 /* require nonrelative corefile path and be extra careful */
530 bool need_suid_safe = false;
531 bool core_dumped = false;
532 static atomic_t core_dump_count = ATOMIC_INIT(0);
533 struct coredump_params cprm = {
534 .siginfo = siginfo,
535 .limit = rlimit(RLIMIT_CORE),
536 /*
537 * We must use the same mm->flags while dumping core to avoid
538 * inconsistency of bit flags, since this flag is not protected
539 * by any locks.
540 */
541 .mm_flags = mm->flags,
542 .vma_meta = NULL,
543 .cpu = raw_smp_processor_id(),
544 };
545
546 audit_core_dumps(siginfo->si_signo);
547
548 binfmt = mm->binfmt;
549 if (!binfmt || !binfmt->core_dump)
550 goto fail;
551 if (!__get_dumpable(cprm.mm_flags))
552 goto fail;
553
554 cred = prepare_creds();
555 if (!cred)
556 goto fail;
557 /*
558 * We cannot trust fsuid as being the "true" uid of the process
559 * nor do we know its entire history. We only know it was tainted
560 * so we dump it as root in mode 2, and only into a controlled
561 * environment (pipe handler or fully qualified path).
562 */
563 if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
564 /* Setuid core dump mode */
565 cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */
566 need_suid_safe = true;
567 }
568
569 retval = coredump_wait(siginfo->si_signo, &core_state);
570 if (retval < 0)
571 goto fail_creds;
572
573 old_cred = override_creds(cred);
574
575 ispipe = format_corename(&cn, &cprm, &argv, &argc);
576
577 if (ispipe) {
578 int argi;
579 int dump_count;
580 char **helper_argv;
581 struct subprocess_info *sub_info;
582
583 if (ispipe < 0) {
584 printk(KERN_WARNING "format_corename failed\n");
585 printk(KERN_WARNING "Aborting core\n");
586 goto fail_unlock;
587 }
588
589 if (cprm.limit == 1) {
590 /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
591 *
592 * Normally core limits are irrelevant to pipes, since
593 * we're not writing to the file system, but we use
594 * cprm.limit of 1 here as a special value, this is a
595 * consistent way to catch recursive crashes.
596 * We can still crash if the core_pattern binary sets
597 * RLIM_CORE = !1, but it runs as root, and can do
598 * lots of stupid things.
599 *
600 * Note that we use task_tgid_vnr here to grab the pid
601 * of the process group leader. That way we get the
602 * right pid if a thread in a multi-threaded
603 * core_pattern process dies.
604 */
605 printk(KERN_WARNING
606 "Process %d(%s) has RLIMIT_CORE set to 1\n",
607 task_tgid_vnr(current), current->comm);
608 printk(KERN_WARNING "Aborting core\n");
609 goto fail_unlock;
610 }
611 cprm.limit = RLIM_INFINITY;
612
613 dump_count = atomic_inc_return(&core_dump_count);
614 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
615 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
616 task_tgid_vnr(current), current->comm);
617 printk(KERN_WARNING "Skipping core dump\n");
618 goto fail_dropcount;
619 }
620
621 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
622 GFP_KERNEL);
623 if (!helper_argv) {
624 printk(KERN_WARNING "%s failed to allocate memory\n",
625 __func__);
626 goto fail_dropcount;
627 }
628 for (argi = 0; argi < argc; argi++)
629 helper_argv[argi] = cn.corename + argv[argi];
630 helper_argv[argi] = NULL;
631
632 retval = -ENOMEM;
633 sub_info = call_usermodehelper_setup(helper_argv[0],
634 helper_argv, NULL, GFP_KERNEL,
635 umh_pipe_setup, NULL, &cprm);
636 if (sub_info)
637 retval = call_usermodehelper_exec(sub_info,
638 UMH_WAIT_EXEC);
639
640 kfree(helper_argv);
641 if (retval) {
642 printk(KERN_INFO "Core dump to |%s pipe failed\n",
643 cn.corename);
644 goto close_fail;
645 }
646 } else {
647 struct mnt_idmap *idmap;
648 struct inode *inode;
649 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
650 O_LARGEFILE | O_EXCL;
651
652 if (cprm.limit < binfmt->min_coredump)
653 goto fail_unlock;
654
655 if (need_suid_safe && cn.corename[0] != '/') {
656 printk(KERN_WARNING "Pid %d(%s) can only dump core "\
657 "to fully qualified path!\n",
658 task_tgid_vnr(current), current->comm);
659 printk(KERN_WARNING "Skipping core dump\n");
660 goto fail_unlock;
661 }
662
663 /*
664 * Unlink the file if it exists unless this is a SUID
665 * binary - in that case, we're running around with root
666 * privs and don't want to unlink another user's coredump.
667 */
668 if (!need_suid_safe) {
669 /*
670 * If it doesn't exist, that's fine. If there's some
671 * other problem, we'll catch it at the filp_open().
672 */
673 do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
674 }
675
676 /*
677 * There is a race between unlinking and creating the
678 * file, but if that causes an EEXIST here, that's
679 * fine - another process raced with us while creating
680 * the corefile, and the other process won. To userspace,
681 * what matters is that at least one of the two processes
682 * writes its coredump successfully, not which one.
683 */
684 if (need_suid_safe) {
685 /*
686 * Using user namespaces, normal user tasks can change
687 * their current->fs->root to point to arbitrary
688 * directories. Since the intention of the "only dump
689 * with a fully qualified path" rule is to control where
690 * coredumps may be placed using root privileges,
691 * current->fs->root must not be used. Instead, use the
692 * root directory of init_task.
693 */
694 struct path root;
695
696 task_lock(&init_task);
697 get_fs_root(init_task.fs, &root);
698 task_unlock(&init_task);
699 cprm.file = file_open_root(&root, cn.corename,
700 open_flags, 0600);
701 path_put(&root);
702 } else {
703 cprm.file = filp_open(cn.corename, open_flags, 0600);
704 }
705 if (IS_ERR(cprm.file))
706 goto fail_unlock;
707
708 inode = file_inode(cprm.file);
709 if (inode->i_nlink > 1)
710 goto close_fail;
711 if (d_unhashed(cprm.file->f_path.dentry))
712 goto close_fail;
713 /*
714 * AK: actually i see no reason to not allow this for named
715 * pipes etc, but keep the previous behaviour for now.
716 */
717 if (!S_ISREG(inode->i_mode))
718 goto close_fail;
719 /*
720 * Don't dump core if the filesystem changed owner or mode
721 * of the file during file creation. This is an issue when
722 * a process dumps core while its cwd is e.g. on a vfat
723 * filesystem.
724 */
725 idmap = file_mnt_idmap(cprm.file);
726 if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode),
727 current_fsuid())) {
728 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n",
729 cn.corename);
730 goto close_fail;
731 }
732 if ((inode->i_mode & 0677) != 0600) {
733 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n",
734 cn.corename);
735 goto close_fail;
736 }
737 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
738 goto close_fail;
739 if (do_truncate(idmap, cprm.file->f_path.dentry,
740 0, 0, cprm.file))
741 goto close_fail;
742 }
743
744 /* get us an unshared descriptor table; almost always a no-op */
745 /* The cell spufs coredump code reads the file descriptor tables */
746 retval = unshare_files();
747 if (retval)
748 goto close_fail;
749 if (!dump_interrupted()) {
750 /*
751 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
752 * have this set to NULL.
753 */
754 if (!cprm.file) {
755 pr_info("Core dump to |%s disabled\n", cn.corename);
756 goto close_fail;
757 }
758 if (!dump_vma_snapshot(&cprm))
759 goto close_fail;
760
761 file_start_write(cprm.file);
762 core_dumped = binfmt->core_dump(&cprm);
763 /*
764 * Ensures that file size is big enough to contain the current
765 * file postion. This prevents gdb from complaining about
766 * a truncated file if the last "write" to the file was
767 * dump_skip.
768 */
769 if (cprm.to_skip) {
770 cprm.to_skip--;
771 dump_emit(&cprm, "", 1);
772 }
773 file_end_write(cprm.file);
774 free_vma_snapshot(&cprm);
775 }
776 if (ispipe && core_pipe_limit)
777 wait_for_dump_helpers(cprm.file);
778 close_fail:
779 if (cprm.file)
780 filp_close(cprm.file, NULL);
781 fail_dropcount:
782 if (ispipe)
783 atomic_dec(&core_dump_count);
784 fail_unlock:
785 kfree(argv);
786 kfree(cn.corename);
787 coredump_finish(core_dumped);
788 revert_creds(old_cred);
789 fail_creds:
790 put_cred(cred);
791 fail:
792 return;
793 }
794
795 /*
796 * Core dumping helper functions. These are the only things you should
797 * do on a core-file: use only these functions to write out all the
798 * necessary info.
799 */
__dump_emit(struct coredump_params * cprm,const void * addr,int nr)800 static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
801 {
802 struct file *file = cprm->file;
803 loff_t pos = file->f_pos;
804 ssize_t n;
805 if (cprm->written + nr > cprm->limit)
806 return 0;
807
808
809 if (dump_interrupted())
810 return 0;
811 n = __kernel_write(file, addr, nr, &pos);
812 if (n != nr)
813 return 0;
814 file->f_pos = pos;
815 cprm->written += n;
816 cprm->pos += n;
817
818 return 1;
819 }
820
__dump_skip(struct coredump_params * cprm,size_t nr)821 static int __dump_skip(struct coredump_params *cprm, size_t nr)
822 {
823 static char zeroes[PAGE_SIZE];
824 struct file *file = cprm->file;
825 if (file->f_mode & FMODE_LSEEK) {
826 if (dump_interrupted() ||
827 vfs_llseek(file, nr, SEEK_CUR) < 0)
828 return 0;
829 cprm->pos += nr;
830 return 1;
831 } else {
832 while (nr > PAGE_SIZE) {
833 if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
834 return 0;
835 nr -= PAGE_SIZE;
836 }
837 return __dump_emit(cprm, zeroes, nr);
838 }
839 }
840
dump_emit(struct coredump_params * cprm,const void * addr,int nr)841 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
842 {
843 if (cprm->to_skip) {
844 if (!__dump_skip(cprm, cprm->to_skip))
845 return 0;
846 cprm->to_skip = 0;
847 }
848 return __dump_emit(cprm, addr, nr);
849 }
850 EXPORT_SYMBOL(dump_emit);
851
dump_skip_to(struct coredump_params * cprm,unsigned long pos)852 void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
853 {
854 cprm->to_skip = pos - cprm->pos;
855 }
856 EXPORT_SYMBOL(dump_skip_to);
857
dump_skip(struct coredump_params * cprm,size_t nr)858 void dump_skip(struct coredump_params *cprm, size_t nr)
859 {
860 cprm->to_skip += nr;
861 }
862 EXPORT_SYMBOL(dump_skip);
863
864 #ifdef CONFIG_ELF_CORE
dump_emit_page(struct coredump_params * cprm,struct page * page)865 static int dump_emit_page(struct coredump_params *cprm, struct page *page)
866 {
867 struct bio_vec bvec;
868 struct iov_iter iter;
869 struct file *file = cprm->file;
870 loff_t pos;
871 ssize_t n;
872
873 if (cprm->to_skip) {
874 if (!__dump_skip(cprm, cprm->to_skip))
875 return 0;
876 cprm->to_skip = 0;
877 }
878 if (cprm->written + PAGE_SIZE > cprm->limit)
879 return 0;
880 if (dump_interrupted())
881 return 0;
882 pos = file->f_pos;
883 bvec_set_page(&bvec, page, PAGE_SIZE, 0);
884 iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE);
885 n = __kernel_write_iter(cprm->file, &iter, &pos);
886 if (n != PAGE_SIZE)
887 return 0;
888 file->f_pos = pos;
889 cprm->written += PAGE_SIZE;
890 cprm->pos += PAGE_SIZE;
891
892 return 1;
893 }
894
dump_user_range(struct coredump_params * cprm,unsigned long start,unsigned long len)895 int dump_user_range(struct coredump_params *cprm, unsigned long start,
896 unsigned long len)
897 {
898 unsigned long addr;
899
900 for (addr = start; addr < start + len; addr += PAGE_SIZE) {
901 struct page *page;
902
903 /*
904 * To avoid having to allocate page tables for virtual address
905 * ranges that have never been used yet, and also to make it
906 * easy to generate sparse core files, use a helper that returns
907 * NULL when encountering an empty page table entry that would
908 * otherwise have been filled with the zero page.
909 */
910 page = get_dump_page(addr);
911 if (page) {
912 int stop = !dump_emit_page(cprm, page);
913 put_page(page);
914 if (stop)
915 return 0;
916 } else {
917 dump_skip(cprm, PAGE_SIZE);
918 }
919 }
920 return 1;
921 }
922 #endif
923
dump_align(struct coredump_params * cprm,int align)924 int dump_align(struct coredump_params *cprm, int align)
925 {
926 unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
927 if (align & (align - 1))
928 return 0;
929 if (mod)
930 cprm->to_skip += align - mod;
931 return 1;
932 }
933 EXPORT_SYMBOL(dump_align);
934
935 #ifdef CONFIG_SYSCTL
936
validate_coredump_safety(void)937 void validate_coredump_safety(void)
938 {
939 if (suid_dumpable == SUID_DUMP_ROOT &&
940 core_pattern[0] != '/' && core_pattern[0] != '|') {
941 pr_warn(
942 "Unsafe core_pattern used with fs.suid_dumpable=2.\n"
943 "Pipe handler or fully qualified core dump path required.\n"
944 "Set kernel.core_pattern before fs.suid_dumpable.\n"
945 );
946 }
947 }
948
proc_dostring_coredump(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)949 static int proc_dostring_coredump(struct ctl_table *table, int write,
950 void *buffer, size_t *lenp, loff_t *ppos)
951 {
952 int error = proc_dostring(table, write, buffer, lenp, ppos);
953
954 if (!error)
955 validate_coredump_safety();
956 return error;
957 }
958
959 static struct ctl_table coredump_sysctls[] = {
960 {
961 .procname = "core_uses_pid",
962 .data = &core_uses_pid,
963 .maxlen = sizeof(int),
964 .mode = 0644,
965 .proc_handler = proc_dointvec,
966 },
967 {
968 .procname = "core_pattern",
969 .data = core_pattern,
970 .maxlen = CORENAME_MAX_SIZE,
971 .mode = 0644,
972 .proc_handler = proc_dostring_coredump,
973 },
974 {
975 .procname = "core_pipe_limit",
976 .data = &core_pipe_limit,
977 .maxlen = sizeof(unsigned int),
978 .mode = 0644,
979 .proc_handler = proc_dointvec,
980 },
981 { }
982 };
983
init_fs_coredump_sysctls(void)984 static int __init init_fs_coredump_sysctls(void)
985 {
986 register_sysctl_init("kernel", coredump_sysctls);
987 return 0;
988 }
989 fs_initcall(init_fs_coredump_sysctls);
990 #endif /* CONFIG_SYSCTL */
991
992 /*
993 * The purpose of always_dump_vma() is to make sure that special kernel mappings
994 * that are useful for post-mortem analysis are included in every core dump.
995 * In that way we ensure that the core dump is fully interpretable later
996 * without matching up the same kernel and hardware config to see what PC values
997 * meant. These special mappings include - vDSO, vsyscall, and other
998 * architecture specific mappings
999 */
always_dump_vma(struct vm_area_struct * vma)1000 static bool always_dump_vma(struct vm_area_struct *vma)
1001 {
1002 /* Any vsyscall mappings? */
1003 if (vma == get_gate_vma(vma->vm_mm))
1004 return true;
1005
1006 /*
1007 * Assume that all vmas with a .name op should always be dumped.
1008 * If this changes, a new vm_ops field can easily be added.
1009 */
1010 if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
1011 return true;
1012
1013 /*
1014 * arch_vma_name() returns non-NULL for special architecture mappings,
1015 * such as vDSO sections.
1016 */
1017 if (arch_vma_name(vma))
1018 return true;
1019
1020 return false;
1021 }
1022
1023 #define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1
1024
1025 /*
1026 * Decide how much of @vma's contents should be included in a core dump.
1027 */
vma_dump_size(struct vm_area_struct * vma,unsigned long mm_flags)1028 static unsigned long vma_dump_size(struct vm_area_struct *vma,
1029 unsigned long mm_flags)
1030 {
1031 #define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
1032
1033 /* always dump the vdso and vsyscall sections */
1034 if (always_dump_vma(vma))
1035 goto whole;
1036
1037 if (vma->vm_flags & VM_DONTDUMP)
1038 return 0;
1039
1040 /* support for DAX */
1041 if (vma_is_dax(vma)) {
1042 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1043 goto whole;
1044 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1045 goto whole;
1046 return 0;
1047 }
1048
1049 /* Hugetlb memory check */
1050 if (is_vm_hugetlb_page(vma)) {
1051 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1052 goto whole;
1053 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1054 goto whole;
1055 return 0;
1056 }
1057
1058 /* Do not dump I/O mapped devices or special mappings */
1059 if (vma->vm_flags & VM_IO)
1060 return 0;
1061
1062 /* By default, dump shared memory if mapped from an anonymous file. */
1063 if (vma->vm_flags & VM_SHARED) {
1064 if (file_inode(vma->vm_file)->i_nlink == 0 ?
1065 FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1066 goto whole;
1067 return 0;
1068 }
1069
1070 /* Dump segments that have been written to. */
1071 if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1072 goto whole;
1073 if (vma->vm_file == NULL)
1074 return 0;
1075
1076 if (FILTER(MAPPED_PRIVATE))
1077 goto whole;
1078
1079 /*
1080 * If this is the beginning of an executable file mapping,
1081 * dump the first page to aid in determining what was mapped here.
1082 */
1083 if (FILTER(ELF_HEADERS) &&
1084 vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
1085 if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1086 return PAGE_SIZE;
1087
1088 /*
1089 * ELF libraries aren't always executable.
1090 * We'll want to check whether the mapping starts with the ELF
1091 * magic, but not now - we're holding the mmap lock,
1092 * so copy_from_user() doesn't work here.
1093 * Use a placeholder instead, and fix it up later in
1094 * dump_vma_snapshot().
1095 */
1096 return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
1097 }
1098
1099 #undef FILTER
1100
1101 return 0;
1102
1103 whole:
1104 return vma->vm_end - vma->vm_start;
1105 }
1106
1107 /*
1108 * Helper function for iterating across a vma list. It ensures that the caller
1109 * will visit `gate_vma' prior to terminating the search.
1110 */
coredump_next_vma(struct vma_iterator * vmi,struct vm_area_struct * vma,struct vm_area_struct * gate_vma)1111 static struct vm_area_struct *coredump_next_vma(struct vma_iterator *vmi,
1112 struct vm_area_struct *vma,
1113 struct vm_area_struct *gate_vma)
1114 {
1115 if (gate_vma && (vma == gate_vma))
1116 return NULL;
1117
1118 vma = vma_next(vmi);
1119 if (vma)
1120 return vma;
1121 return gate_vma;
1122 }
1123
free_vma_snapshot(struct coredump_params * cprm)1124 static void free_vma_snapshot(struct coredump_params *cprm)
1125 {
1126 if (cprm->vma_meta) {
1127 int i;
1128 for (i = 0; i < cprm->vma_count; i++) {
1129 struct file *file = cprm->vma_meta[i].file;
1130 if (file)
1131 fput(file);
1132 }
1133 kvfree(cprm->vma_meta);
1134 cprm->vma_meta = NULL;
1135 }
1136 }
1137
1138 /*
1139 * Under the mmap_lock, take a snapshot of relevant information about the task's
1140 * VMAs.
1141 */
dump_vma_snapshot(struct coredump_params * cprm)1142 static bool dump_vma_snapshot(struct coredump_params *cprm)
1143 {
1144 struct vm_area_struct *gate_vma, *vma = NULL;
1145 struct mm_struct *mm = current->mm;
1146 VMA_ITERATOR(vmi, mm, 0);
1147 int i = 0;
1148
1149 /*
1150 * Once the stack expansion code is fixed to not change VMA bounds
1151 * under mmap_lock in read mode, this can be changed to take the
1152 * mmap_lock in read mode.
1153 */
1154 if (mmap_write_lock_killable(mm))
1155 return false;
1156
1157 cprm->vma_data_size = 0;
1158 gate_vma = get_gate_vma(mm);
1159 cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
1160
1161 cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
1162 if (!cprm->vma_meta) {
1163 mmap_write_unlock(mm);
1164 return false;
1165 }
1166
1167 while ((vma = coredump_next_vma(&vmi, vma, gate_vma)) != NULL) {
1168 struct core_vma_metadata *m = cprm->vma_meta + i;
1169
1170 m->start = vma->vm_start;
1171 m->end = vma->vm_end;
1172 m->flags = vma->vm_flags;
1173 m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1174 m->pgoff = vma->vm_pgoff;
1175 m->file = vma->vm_file;
1176 if (m->file)
1177 get_file(m->file);
1178 i++;
1179 }
1180
1181 mmap_write_unlock(mm);
1182
1183 for (i = 0; i < cprm->vma_count; i++) {
1184 struct core_vma_metadata *m = cprm->vma_meta + i;
1185
1186 if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
1187 char elfmag[SELFMAG];
1188
1189 if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
1190 memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
1191 m->dump_size = 0;
1192 } else {
1193 m->dump_size = PAGE_SIZE;
1194 }
1195 }
1196
1197 cprm->vma_data_size += m->dump_size;
1198 }
1199
1200 return true;
1201 }
1202