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/sort.h>
22 #include <linux/sched/coredump.h>
23 #include <linux/sched/signal.h>
24 #include <linux/sched/task_stack.h>
25 #include <linux/utsname.h>
26 #include <linux/pid_namespace.h>
27 #include <linux/module.h>
28 #include <linux/namei.h>
29 #include <linux/mount.h>
30 #include <linux/security.h>
31 #include <linux/syscalls.h>
32 #include <linux/tsacct_kern.h>
33 #include <linux/cn_proc.h>
34 #include <linux/audit.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/sysctl.h>
45 #include <linux/elf.h>
46
47 #include <linux/uaccess.h>
48 #include <asm/mmu_context.h>
49 #include <asm/tlb.h>
50 #include <asm/exec.h>
51
52 #include <trace/events/task.h>
53 #include "internal.h"
54
55 #include <trace/events/sched.h>
56
57 static bool dump_vma_snapshot(struct coredump_params *cprm);
58 static void free_vma_snapshot(struct coredump_params *cprm);
59
60 #define CORE_FILE_NOTE_SIZE_DEFAULT (4*1024*1024)
61 /* Define a reasonable max cap */
62 #define CORE_FILE_NOTE_SIZE_MAX (16*1024*1024)
63
64 static int core_uses_pid;
65 static unsigned int core_pipe_limit;
66 static char core_pattern[CORENAME_MAX_SIZE] = "core";
67 static int core_name_size = CORENAME_MAX_SIZE;
68 unsigned int core_file_note_size_limit = CORE_FILE_NOTE_SIZE_DEFAULT;
69
70 struct core_name {
71 char *corename;
72 int used, size;
73 };
74
expand_corename(struct core_name * cn,int size)75 static int expand_corename(struct core_name *cn, int size)
76 {
77 char *corename;
78
79 size = kmalloc_size_roundup(size);
80 corename = krealloc(cn->corename, size, GFP_KERNEL);
81
82 if (!corename)
83 return -ENOMEM;
84
85 if (size > core_name_size) /* racy but harmless */
86 core_name_size = size;
87
88 cn->size = size;
89 cn->corename = corename;
90 return 0;
91 }
92
cn_vprintf(struct core_name * cn,const char * fmt,va_list arg)93 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
94 va_list arg)
95 {
96 int free, need;
97 va_list arg_copy;
98
99 again:
100 free = cn->size - cn->used;
101
102 va_copy(arg_copy, arg);
103 need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
104 va_end(arg_copy);
105
106 if (need < free) {
107 cn->used += need;
108 return 0;
109 }
110
111 if (!expand_corename(cn, cn->size + need - free + 1))
112 goto again;
113
114 return -ENOMEM;
115 }
116
cn_printf(struct core_name * cn,const char * fmt,...)117 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
118 {
119 va_list arg;
120 int ret;
121
122 va_start(arg, fmt);
123 ret = cn_vprintf(cn, fmt, arg);
124 va_end(arg);
125
126 return ret;
127 }
128
129 static __printf(2, 3)
cn_esc_printf(struct core_name * cn,const char * fmt,...)130 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
131 {
132 int cur = cn->used;
133 va_list arg;
134 int ret;
135
136 va_start(arg, fmt);
137 ret = cn_vprintf(cn, fmt, arg);
138 va_end(arg);
139
140 if (ret == 0) {
141 /*
142 * Ensure that this coredump name component can't cause the
143 * resulting corefile path to consist of a ".." or ".".
144 */
145 if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
146 (cn->used - cur == 2 && cn->corename[cur] == '.'
147 && cn->corename[cur+1] == '.'))
148 cn->corename[cur] = '!';
149
150 /*
151 * Empty names are fishy and could be used to create a "//" in a
152 * corefile name, causing the coredump to happen one directory
153 * level too high. Enforce that all components of the core
154 * pattern are at least one character long.
155 */
156 if (cn->used == cur)
157 ret = cn_printf(cn, "!");
158 }
159
160 for (; cur < cn->used; ++cur) {
161 if (cn->corename[cur] == '/')
162 cn->corename[cur] = '!';
163 }
164 return ret;
165 }
166
cn_print_exe_file(struct core_name * cn,bool name_only)167 static int cn_print_exe_file(struct core_name *cn, bool name_only)
168 {
169 struct file *exe_file;
170 char *pathbuf, *path, *ptr;
171 int ret;
172
173 exe_file = get_mm_exe_file(current->mm);
174 if (!exe_file)
175 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
176
177 pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
178 if (!pathbuf) {
179 ret = -ENOMEM;
180 goto put_exe_file;
181 }
182
183 path = file_path(exe_file, pathbuf, PATH_MAX);
184 if (IS_ERR(path)) {
185 ret = PTR_ERR(path);
186 goto free_buf;
187 }
188
189 if (name_only) {
190 ptr = strrchr(path, '/');
191 if (ptr)
192 path = ptr + 1;
193 }
194 ret = cn_esc_printf(cn, "%s", path);
195
196 free_buf:
197 kfree(pathbuf);
198 put_exe_file:
199 fput(exe_file);
200 return ret;
201 }
202
203 /* format_corename will inspect the pattern parameter, and output a
204 * name into corename, which must have space for at least
205 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
206 */
format_corename(struct core_name * cn,struct coredump_params * cprm,size_t ** argv,int * argc)207 static int format_corename(struct core_name *cn, struct coredump_params *cprm,
208 size_t **argv, int *argc)
209 {
210 const struct cred *cred = current_cred();
211 const char *pat_ptr = core_pattern;
212 int ispipe = (*pat_ptr == '|');
213 bool was_space = false;
214 int pid_in_pattern = 0;
215 int err = 0;
216
217 cn->used = 0;
218 cn->corename = NULL;
219 if (expand_corename(cn, core_name_size))
220 return -ENOMEM;
221 cn->corename[0] = '\0';
222
223 if (ispipe) {
224 int argvs = sizeof(core_pattern) / 2;
225 (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
226 if (!(*argv))
227 return -ENOMEM;
228 (*argv)[(*argc)++] = 0;
229 ++pat_ptr;
230 if (!(*pat_ptr))
231 return -ENOMEM;
232 }
233
234 /* Repeat as long as we have more pattern to process and more output
235 space */
236 while (*pat_ptr) {
237 /*
238 * Split on spaces before doing template expansion so that
239 * %e and %E don't get split if they have spaces in them
240 */
241 if (ispipe) {
242 if (isspace(*pat_ptr)) {
243 if (cn->used != 0)
244 was_space = true;
245 pat_ptr++;
246 continue;
247 } else if (was_space) {
248 was_space = false;
249 err = cn_printf(cn, "%c", '\0');
250 if (err)
251 return err;
252 (*argv)[(*argc)++] = cn->used;
253 }
254 }
255 if (*pat_ptr != '%') {
256 err = cn_printf(cn, "%c", *pat_ptr++);
257 } else {
258 switch (*++pat_ptr) {
259 /* single % at the end, drop that */
260 case 0:
261 goto out;
262 /* Double percent, output one percent */
263 case '%':
264 err = cn_printf(cn, "%c", '%');
265 break;
266 /* pid */
267 case 'p':
268 pid_in_pattern = 1;
269 err = cn_printf(cn, "%d",
270 task_tgid_vnr(current));
271 break;
272 /* global pid */
273 case 'P':
274 err = cn_printf(cn, "%d",
275 task_tgid_nr(current));
276 break;
277 case 'i':
278 err = cn_printf(cn, "%d",
279 task_pid_vnr(current));
280 break;
281 case 'I':
282 err = cn_printf(cn, "%d",
283 task_pid_nr(current));
284 break;
285 /* uid */
286 case 'u':
287 err = cn_printf(cn, "%u",
288 from_kuid(&init_user_ns,
289 cred->uid));
290 break;
291 /* gid */
292 case 'g':
293 err = cn_printf(cn, "%u",
294 from_kgid(&init_user_ns,
295 cred->gid));
296 break;
297 case 'd':
298 err = cn_printf(cn, "%d",
299 __get_dumpable(cprm->mm_flags));
300 break;
301 /* signal that caused the coredump */
302 case 's':
303 err = cn_printf(cn, "%d",
304 cprm->siginfo->si_signo);
305 break;
306 /* UNIX time of coredump */
307 case 't': {
308 time64_t time;
309
310 time = ktime_get_real_seconds();
311 err = cn_printf(cn, "%lld", time);
312 break;
313 }
314 /* hostname */
315 case 'h':
316 down_read(&uts_sem);
317 err = cn_esc_printf(cn, "%s",
318 utsname()->nodename);
319 up_read(&uts_sem);
320 break;
321 /* executable, could be changed by prctl PR_SET_NAME etc */
322 case 'e':
323 err = cn_esc_printf(cn, "%s", current->comm);
324 break;
325 /* file name of executable */
326 case 'f':
327 err = cn_print_exe_file(cn, true);
328 break;
329 case 'E':
330 err = cn_print_exe_file(cn, false);
331 break;
332 /* core limit size */
333 case 'c':
334 err = cn_printf(cn, "%lu",
335 rlimit(RLIMIT_CORE));
336 break;
337 /* CPU the task ran on */
338 case 'C':
339 err = cn_printf(cn, "%d", cprm->cpu);
340 break;
341 default:
342 break;
343 }
344 ++pat_ptr;
345 }
346
347 if (err)
348 return err;
349 }
350
351 out:
352 /* Backward compatibility with core_uses_pid:
353 *
354 * If core_pattern does not include a %p (as is the default)
355 * and core_uses_pid is set, then .%pid will be appended to
356 * the filename. Do not do this for piped commands. */
357 if (!ispipe && !pid_in_pattern && core_uses_pid) {
358 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
359 if (err)
360 return err;
361 }
362 return ispipe;
363 }
364
zap_process(struct signal_struct * signal,int exit_code)365 static int zap_process(struct signal_struct *signal, int exit_code)
366 {
367 struct task_struct *t;
368 int nr = 0;
369
370 signal->flags = SIGNAL_GROUP_EXIT;
371 signal->group_exit_code = exit_code;
372 signal->group_stop_count = 0;
373
374 __for_each_thread(signal, t) {
375 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
376 if (t != current && !(t->flags & PF_POSTCOREDUMP)) {
377 sigaddset(&t->pending.signal, SIGKILL);
378 signal_wake_up(t, 1);
379 nr++;
380 }
381 }
382
383 return nr;
384 }
385
zap_threads(struct task_struct * tsk,struct core_state * core_state,int exit_code)386 static int zap_threads(struct task_struct *tsk,
387 struct core_state *core_state, int exit_code)
388 {
389 struct signal_struct *signal = tsk->signal;
390 int nr = -EAGAIN;
391
392 spin_lock_irq(&tsk->sighand->siglock);
393 if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) {
394 /* Allow SIGKILL, see prepare_signal() */
395 signal->core_state = core_state;
396 nr = zap_process(signal, exit_code);
397 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
398 tsk->flags |= PF_DUMPCORE;
399 atomic_set(&core_state->nr_threads, nr);
400 }
401 spin_unlock_irq(&tsk->sighand->siglock);
402 return nr;
403 }
404
coredump_wait(int exit_code,struct core_state * core_state)405 static int coredump_wait(int exit_code, struct core_state *core_state)
406 {
407 struct task_struct *tsk = current;
408 int core_waiters = -EBUSY;
409
410 init_completion(&core_state->startup);
411 core_state->dumper.task = tsk;
412 core_state->dumper.next = NULL;
413
414 core_waiters = zap_threads(tsk, core_state, exit_code);
415 if (core_waiters > 0) {
416 struct core_thread *ptr;
417
418 wait_for_completion_state(&core_state->startup,
419 TASK_UNINTERRUPTIBLE|TASK_FREEZABLE);
420 /*
421 * Wait for all the threads to become inactive, so that
422 * all the thread context (extended register state, like
423 * fpu etc) gets copied to the memory.
424 */
425 ptr = core_state->dumper.next;
426 while (ptr != NULL) {
427 wait_task_inactive(ptr->task, TASK_ANY);
428 ptr = ptr->next;
429 }
430 }
431
432 return core_waiters;
433 }
434
coredump_finish(bool core_dumped)435 static void coredump_finish(bool core_dumped)
436 {
437 struct core_thread *curr, *next;
438 struct task_struct *task;
439
440 spin_lock_irq(¤t->sighand->siglock);
441 if (core_dumped && !__fatal_signal_pending(current))
442 current->signal->group_exit_code |= 0x80;
443 next = current->signal->core_state->dumper.next;
444 current->signal->core_state = NULL;
445 spin_unlock_irq(¤t->sighand->siglock);
446
447 while ((curr = next) != NULL) {
448 next = curr->next;
449 task = curr->task;
450 /*
451 * see coredump_task_exit(), curr->task must not see
452 * ->task == NULL before we read ->next.
453 */
454 smp_mb();
455 curr->task = NULL;
456 wake_up_process(task);
457 }
458 }
459
dump_interrupted(void)460 static bool dump_interrupted(void)
461 {
462 /*
463 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
464 * can do try_to_freeze() and check __fatal_signal_pending(),
465 * but then we need to teach dump_write() to restart and clear
466 * TIF_SIGPENDING.
467 */
468 return fatal_signal_pending(current) || freezing(current);
469 }
470
wait_for_dump_helpers(struct file * file)471 static void wait_for_dump_helpers(struct file *file)
472 {
473 struct pipe_inode_info *pipe = file->private_data;
474
475 pipe_lock(pipe);
476 pipe->readers++;
477 pipe->writers--;
478 wake_up_interruptible_sync(&pipe->rd_wait);
479 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
480 pipe_unlock(pipe);
481
482 /*
483 * We actually want wait_event_freezable() but then we need
484 * to clear TIF_SIGPENDING and improve dump_interrupted().
485 */
486 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
487
488 pipe_lock(pipe);
489 pipe->readers--;
490 pipe->writers++;
491 pipe_unlock(pipe);
492 }
493
494 /*
495 * umh_pipe_setup
496 * helper function to customize the process used
497 * to collect the core in userspace. Specifically
498 * it sets up a pipe and installs it as fd 0 (stdin)
499 * for the process. Returns 0 on success, or
500 * PTR_ERR on failure.
501 * Note that it also sets the core limit to 1. This
502 * is a special value that we use to trap recursive
503 * core dumps
504 */
umh_pipe_setup(struct subprocess_info * info,struct cred * new)505 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
506 {
507 struct file *files[2];
508 struct coredump_params *cp = (struct coredump_params *)info->data;
509 int err = create_pipe_files(files, 0);
510 if (err)
511 return err;
512
513 cp->file = files[1];
514
515 err = replace_fd(0, files[0], 0);
516 fput(files[0]);
517 /* and disallow core files too */
518 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
519
520 return err;
521 }
522
do_coredump(const kernel_siginfo_t * siginfo)523 void do_coredump(const kernel_siginfo_t *siginfo)
524 {
525 struct core_state core_state;
526 struct core_name cn;
527 struct mm_struct *mm = current->mm;
528 struct linux_binfmt * binfmt;
529 const struct cred *old_cred;
530 struct cred *cred;
531 int retval = 0;
532 int ispipe;
533 size_t *argv = NULL;
534 int argc = 0;
535 /* require nonrelative corefile path and be extra careful */
536 bool need_suid_safe = false;
537 bool core_dumped = false;
538 static atomic_t core_dump_count = ATOMIC_INIT(0);
539 struct coredump_params cprm = {
540 .siginfo = siginfo,
541 .limit = rlimit(RLIMIT_CORE),
542 /*
543 * We must use the same mm->flags while dumping core to avoid
544 * inconsistency of bit flags, since this flag is not protected
545 * by any locks.
546 */
547 .mm_flags = mm->flags,
548 .vma_meta = NULL,
549 .cpu = raw_smp_processor_id(),
550 };
551
552 audit_core_dumps(siginfo->si_signo);
553
554 binfmt = mm->binfmt;
555 if (!binfmt || !binfmt->core_dump)
556 goto fail;
557 if (!__get_dumpable(cprm.mm_flags))
558 goto fail;
559
560 cred = prepare_creds();
561 if (!cred)
562 goto fail;
563 /*
564 * We cannot trust fsuid as being the "true" uid of the process
565 * nor do we know its entire history. We only know it was tainted
566 * so we dump it as root in mode 2, and only into a controlled
567 * environment (pipe handler or fully qualified path).
568 */
569 if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
570 /* Setuid core dump mode */
571 cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */
572 need_suid_safe = true;
573 }
574
575 retval = coredump_wait(siginfo->si_signo, &core_state);
576 if (retval < 0)
577 goto fail_creds;
578
579 old_cred = override_creds(cred);
580
581 ispipe = format_corename(&cn, &cprm, &argv, &argc);
582
583 if (ispipe) {
584 int argi;
585 int dump_count;
586 char **helper_argv;
587 struct subprocess_info *sub_info;
588
589 if (ispipe < 0) {
590 coredump_report_failure("format_corename failed, aborting core");
591 goto fail_unlock;
592 }
593
594 if (cprm.limit == 1) {
595 /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
596 *
597 * Normally core limits are irrelevant to pipes, since
598 * we're not writing to the file system, but we use
599 * cprm.limit of 1 here as a special value, this is a
600 * consistent way to catch recursive crashes.
601 * We can still crash if the core_pattern binary sets
602 * RLIM_CORE = !1, but it runs as root, and can do
603 * lots of stupid things.
604 *
605 * Note that we use task_tgid_vnr here to grab the pid
606 * of the process group leader. That way we get the
607 * right pid if a thread in a multi-threaded
608 * core_pattern process dies.
609 */
610 coredump_report_failure("RLIMIT_CORE is set to 1, aborting core");
611 goto fail_unlock;
612 }
613 cprm.limit = RLIM_INFINITY;
614
615 dump_count = atomic_inc_return(&core_dump_count);
616 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
617 coredump_report_failure("over core_pipe_limit, skipping core dump");
618 goto fail_dropcount;
619 }
620
621 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
622 GFP_KERNEL);
623 if (!helper_argv) {
624 coredump_report_failure("%s failed to allocate memory", __func__);
625 goto fail_dropcount;
626 }
627 for (argi = 0; argi < argc; argi++)
628 helper_argv[argi] = cn.corename + argv[argi];
629 helper_argv[argi] = NULL;
630
631 retval = -ENOMEM;
632 sub_info = call_usermodehelper_setup(helper_argv[0],
633 helper_argv, NULL, GFP_KERNEL,
634 umh_pipe_setup, NULL, &cprm);
635 if (sub_info)
636 retval = call_usermodehelper_exec(sub_info,
637 UMH_WAIT_EXEC);
638
639 kfree(helper_argv);
640 if (retval) {
641 coredump_report_failure("|%s pipe failed", cn.corename);
642 goto close_fail;
643 }
644 } else {
645 struct mnt_idmap *idmap;
646 struct inode *inode;
647 int open_flags = O_CREAT | O_WRONLY | O_NOFOLLOW |
648 O_LARGEFILE | O_EXCL;
649
650 if (cprm.limit < binfmt->min_coredump)
651 goto fail_unlock;
652
653 if (need_suid_safe && cn.corename[0] != '/') {
654 coredump_report_failure(
655 "this process can only dump core to a fully qualified path, skipping core dump");
656 goto fail_unlock;
657 }
658
659 /*
660 * Unlink the file if it exists unless this is a SUID
661 * binary - in that case, we're running around with root
662 * privs and don't want to unlink another user's coredump.
663 */
664 if (!need_suid_safe) {
665 /*
666 * If it doesn't exist, that's fine. If there's some
667 * other problem, we'll catch it at the filp_open().
668 */
669 do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
670 }
671
672 /*
673 * There is a race between unlinking and creating the
674 * file, but if that causes an EEXIST here, that's
675 * fine - another process raced with us while creating
676 * the corefile, and the other process won. To userspace,
677 * what matters is that at least one of the two processes
678 * writes its coredump successfully, not which one.
679 */
680 if (need_suid_safe) {
681 /*
682 * Using user namespaces, normal user tasks can change
683 * their current->fs->root to point to arbitrary
684 * directories. Since the intention of the "only dump
685 * with a fully qualified path" rule is to control where
686 * coredumps may be placed using root privileges,
687 * current->fs->root must not be used. Instead, use the
688 * root directory of init_task.
689 */
690 struct path root;
691
692 task_lock(&init_task);
693 get_fs_root(init_task.fs, &root);
694 task_unlock(&init_task);
695 cprm.file = file_open_root(&root, cn.corename,
696 open_flags, 0600);
697 path_put(&root);
698 } else {
699 cprm.file = filp_open(cn.corename, open_flags, 0600);
700 }
701 if (IS_ERR(cprm.file))
702 goto fail_unlock;
703
704 inode = file_inode(cprm.file);
705 if (inode->i_nlink > 1)
706 goto close_fail;
707 if (d_unhashed(cprm.file->f_path.dentry))
708 goto close_fail;
709 /*
710 * AK: actually i see no reason to not allow this for named
711 * pipes etc, but keep the previous behaviour for now.
712 */
713 if (!S_ISREG(inode->i_mode))
714 goto close_fail;
715 /*
716 * Don't dump core if the filesystem changed owner or mode
717 * of the file during file creation. This is an issue when
718 * a process dumps core while its cwd is e.g. on a vfat
719 * filesystem.
720 */
721 idmap = file_mnt_idmap(cprm.file);
722 if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode),
723 current_fsuid())) {
724 coredump_report_failure("Core dump to %s aborted: "
725 "cannot preserve file owner", cn.corename);
726 goto close_fail;
727 }
728 if ((inode->i_mode & 0677) != 0600) {
729 coredump_report_failure("Core dump to %s aborted: "
730 "cannot preserve file permissions", cn.corename);
731 goto close_fail;
732 }
733 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
734 goto close_fail;
735 if (do_truncate(idmap, cprm.file->f_path.dentry,
736 0, 0, cprm.file))
737 goto close_fail;
738 }
739
740 /* get us an unshared descriptor table; almost always a no-op */
741 /* The cell spufs coredump code reads the file descriptor tables */
742 retval = unshare_files();
743 if (retval)
744 goto close_fail;
745 if (!dump_interrupted()) {
746 /*
747 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
748 * have this set to NULL.
749 */
750 if (!cprm.file) {
751 coredump_report_failure("Core dump to |%s disabled", cn.corename);
752 goto close_fail;
753 }
754 if (!dump_vma_snapshot(&cprm))
755 goto close_fail;
756
757 file_start_write(cprm.file);
758 core_dumped = binfmt->core_dump(&cprm);
759 /*
760 * Ensures that file size is big enough to contain the current
761 * file postion. This prevents gdb from complaining about
762 * a truncated file if the last "write" to the file was
763 * dump_skip.
764 */
765 if (cprm.to_skip) {
766 cprm.to_skip--;
767 dump_emit(&cprm, "", 1);
768 }
769 file_end_write(cprm.file);
770 free_vma_snapshot(&cprm);
771 }
772 if (ispipe && core_pipe_limit)
773 wait_for_dump_helpers(cprm.file);
774 close_fail:
775 if (cprm.file)
776 filp_close(cprm.file, NULL);
777 fail_dropcount:
778 if (ispipe)
779 atomic_dec(&core_dump_count);
780 fail_unlock:
781 kfree(argv);
782 kfree(cn.corename);
783 coredump_finish(core_dumped);
784 revert_creds(old_cred);
785 fail_creds:
786 put_cred(cred);
787 fail:
788 return;
789 }
790
791 /*
792 * Core dumping helper functions. These are the only things you should
793 * do on a core-file: use only these functions to write out all the
794 * necessary info.
795 */
__dump_emit(struct coredump_params * cprm,const void * addr,int nr)796 static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
797 {
798 struct file *file = cprm->file;
799 loff_t pos = file->f_pos;
800 ssize_t n;
801 if (cprm->written + nr > cprm->limit)
802 return 0;
803
804
805 if (dump_interrupted())
806 return 0;
807 n = __kernel_write(file, addr, nr, &pos);
808 if (n != nr)
809 return 0;
810 file->f_pos = pos;
811 cprm->written += n;
812 cprm->pos += n;
813
814 return 1;
815 }
816
__dump_skip(struct coredump_params * cprm,size_t nr)817 static int __dump_skip(struct coredump_params *cprm, size_t nr)
818 {
819 static char zeroes[PAGE_SIZE];
820 struct file *file = cprm->file;
821 if (file->f_mode & FMODE_LSEEK) {
822 if (dump_interrupted() ||
823 vfs_llseek(file, nr, SEEK_CUR) < 0)
824 return 0;
825 cprm->pos += nr;
826 return 1;
827 } else {
828 while (nr > PAGE_SIZE) {
829 if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
830 return 0;
831 nr -= PAGE_SIZE;
832 }
833 return __dump_emit(cprm, zeroes, nr);
834 }
835 }
836
dump_emit(struct coredump_params * cprm,const void * addr,int nr)837 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
838 {
839 if (cprm->to_skip) {
840 if (!__dump_skip(cprm, cprm->to_skip))
841 return 0;
842 cprm->to_skip = 0;
843 }
844 return __dump_emit(cprm, addr, nr);
845 }
846 EXPORT_SYMBOL(dump_emit);
847
dump_skip_to(struct coredump_params * cprm,unsigned long pos)848 void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
849 {
850 cprm->to_skip = pos - cprm->pos;
851 }
852 EXPORT_SYMBOL(dump_skip_to);
853
dump_skip(struct coredump_params * cprm,size_t nr)854 void dump_skip(struct coredump_params *cprm, size_t nr)
855 {
856 cprm->to_skip += nr;
857 }
858 EXPORT_SYMBOL(dump_skip);
859
860 #ifdef CONFIG_ELF_CORE
dump_emit_page(struct coredump_params * cprm,struct page * page)861 static int dump_emit_page(struct coredump_params *cprm, struct page *page)
862 {
863 struct bio_vec bvec;
864 struct iov_iter iter;
865 struct file *file = cprm->file;
866 loff_t pos;
867 ssize_t n;
868
869 if (!page)
870 return 0;
871
872 if (cprm->to_skip) {
873 if (!__dump_skip(cprm, cprm->to_skip))
874 return 0;
875 cprm->to_skip = 0;
876 }
877 if (cprm->written + PAGE_SIZE > cprm->limit)
878 return 0;
879 if (dump_interrupted())
880 return 0;
881 pos = file->f_pos;
882 bvec_set_page(&bvec, page, PAGE_SIZE, 0);
883 iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE);
884 n = __kernel_write_iter(cprm->file, &iter, &pos);
885 if (n != PAGE_SIZE)
886 return 0;
887 file->f_pos = pos;
888 cprm->written += PAGE_SIZE;
889 cprm->pos += PAGE_SIZE;
890
891 return 1;
892 }
893
894 /*
895 * If we might get machine checks from kernel accesses during the
896 * core dump, let's get those errors early rather than during the
897 * IO. This is not performance-critical enough to warrant having
898 * all the machine check logic in the iovec paths.
899 */
900 #ifdef copy_mc_to_kernel
901
902 #define dump_page_alloc() alloc_page(GFP_KERNEL)
903 #define dump_page_free(x) __free_page(x)
dump_page_copy(struct page * src,struct page * dst)904 static struct page *dump_page_copy(struct page *src, struct page *dst)
905 {
906 void *buf = kmap_local_page(src);
907 size_t left = copy_mc_to_kernel(page_address(dst), buf, PAGE_SIZE);
908 kunmap_local(buf);
909 return left ? NULL : dst;
910 }
911
912 #else
913
914 /* We just want to return non-NULL; it's never used. */
915 #define dump_page_alloc() ERR_PTR(-EINVAL)
916 #define dump_page_free(x) ((void)(x))
dump_page_copy(struct page * src,struct page * dst)917 static inline struct page *dump_page_copy(struct page *src, struct page *dst)
918 {
919 return src;
920 }
921 #endif
922
dump_user_range(struct coredump_params * cprm,unsigned long start,unsigned long len)923 int dump_user_range(struct coredump_params *cprm, unsigned long start,
924 unsigned long len)
925 {
926 unsigned long addr;
927 struct page *dump_page;
928
929 dump_page = dump_page_alloc();
930 if (!dump_page)
931 return 0;
932
933 for (addr = start; addr < start + len; addr += PAGE_SIZE) {
934 struct page *page;
935
936 /*
937 * To avoid having to allocate page tables for virtual address
938 * ranges that have never been used yet, and also to make it
939 * easy to generate sparse core files, use a helper that returns
940 * NULL when encountering an empty page table entry that would
941 * otherwise have been filled with the zero page.
942 */
943 page = get_dump_page(addr);
944 if (page) {
945 int stop = !dump_emit_page(cprm, dump_page_copy(page, dump_page));
946 put_page(page);
947 if (stop) {
948 dump_page_free(dump_page);
949 return 0;
950 }
951 } else {
952 dump_skip(cprm, PAGE_SIZE);
953 }
954 }
955 dump_page_free(dump_page);
956 return 1;
957 }
958 #endif
959
dump_align(struct coredump_params * cprm,int align)960 int dump_align(struct coredump_params *cprm, int align)
961 {
962 unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
963 if (align & (align - 1))
964 return 0;
965 if (mod)
966 cprm->to_skip += align - mod;
967 return 1;
968 }
969 EXPORT_SYMBOL(dump_align);
970
971 #ifdef CONFIG_SYSCTL
972
validate_coredump_safety(void)973 void validate_coredump_safety(void)
974 {
975 if (suid_dumpable == SUID_DUMP_ROOT &&
976 core_pattern[0] != '/' && core_pattern[0] != '|') {
977
978 coredump_report_failure("Unsafe core_pattern used with fs.suid_dumpable=2: "
979 "pipe handler or fully qualified core dump path required. "
980 "Set kernel.core_pattern before fs.suid_dumpable.");
981 }
982 }
983
proc_dostring_coredump(const struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)984 static int proc_dostring_coredump(const struct ctl_table *table, int write,
985 void *buffer, size_t *lenp, loff_t *ppos)
986 {
987 int error = proc_dostring(table, write, buffer, lenp, ppos);
988
989 if (!error)
990 validate_coredump_safety();
991 return error;
992 }
993
994 static const unsigned int core_file_note_size_min = CORE_FILE_NOTE_SIZE_DEFAULT;
995 static const unsigned int core_file_note_size_max = CORE_FILE_NOTE_SIZE_MAX;
996
997 static struct ctl_table coredump_sysctls[] = {
998 {
999 .procname = "core_uses_pid",
1000 .data = &core_uses_pid,
1001 .maxlen = sizeof(int),
1002 .mode = 0644,
1003 .proc_handler = proc_dointvec,
1004 },
1005 {
1006 .procname = "core_pattern",
1007 .data = core_pattern,
1008 .maxlen = CORENAME_MAX_SIZE,
1009 .mode = 0644,
1010 .proc_handler = proc_dostring_coredump,
1011 },
1012 {
1013 .procname = "core_pipe_limit",
1014 .data = &core_pipe_limit,
1015 .maxlen = sizeof(unsigned int),
1016 .mode = 0644,
1017 .proc_handler = proc_dointvec,
1018 },
1019 {
1020 .procname = "core_file_note_size_limit",
1021 .data = &core_file_note_size_limit,
1022 .maxlen = sizeof(unsigned int),
1023 .mode = 0644,
1024 .proc_handler = proc_douintvec_minmax,
1025 .extra1 = (unsigned int *)&core_file_note_size_min,
1026 .extra2 = (unsigned int *)&core_file_note_size_max,
1027 },
1028 };
1029
init_fs_coredump_sysctls(void)1030 static int __init init_fs_coredump_sysctls(void)
1031 {
1032 register_sysctl_init("kernel", coredump_sysctls);
1033 return 0;
1034 }
1035 fs_initcall(init_fs_coredump_sysctls);
1036 #endif /* CONFIG_SYSCTL */
1037
1038 /*
1039 * The purpose of always_dump_vma() is to make sure that special kernel mappings
1040 * that are useful for post-mortem analysis are included in every core dump.
1041 * In that way we ensure that the core dump is fully interpretable later
1042 * without matching up the same kernel and hardware config to see what PC values
1043 * meant. These special mappings include - vDSO, vsyscall, and other
1044 * architecture specific mappings
1045 */
always_dump_vma(struct vm_area_struct * vma)1046 static bool always_dump_vma(struct vm_area_struct *vma)
1047 {
1048 /* Any vsyscall mappings? */
1049 if (vma == get_gate_vma(vma->vm_mm))
1050 return true;
1051
1052 /*
1053 * Assume that all vmas with a .name op should always be dumped.
1054 * If this changes, a new vm_ops field can easily be added.
1055 */
1056 if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
1057 return true;
1058
1059 /*
1060 * arch_vma_name() returns non-NULL for special architecture mappings,
1061 * such as vDSO sections.
1062 */
1063 if (arch_vma_name(vma))
1064 return true;
1065
1066 return false;
1067 }
1068
1069 #define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1
1070
1071 /*
1072 * Decide how much of @vma's contents should be included in a core dump.
1073 */
vma_dump_size(struct vm_area_struct * vma,unsigned long mm_flags)1074 static unsigned long vma_dump_size(struct vm_area_struct *vma,
1075 unsigned long mm_flags)
1076 {
1077 #define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
1078
1079 /* always dump the vdso and vsyscall sections */
1080 if (always_dump_vma(vma))
1081 goto whole;
1082
1083 if (vma->vm_flags & VM_DONTDUMP)
1084 return 0;
1085
1086 /* support for DAX */
1087 if (vma_is_dax(vma)) {
1088 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
1089 goto whole;
1090 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
1091 goto whole;
1092 return 0;
1093 }
1094
1095 /* Hugetlb memory check */
1096 if (is_vm_hugetlb_page(vma)) {
1097 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
1098 goto whole;
1099 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
1100 goto whole;
1101 return 0;
1102 }
1103
1104 /* Do not dump I/O mapped devices or special mappings */
1105 if (vma->vm_flags & VM_IO)
1106 return 0;
1107
1108 /* By default, dump shared memory if mapped from an anonymous file. */
1109 if (vma->vm_flags & VM_SHARED) {
1110 if (file_inode(vma->vm_file)->i_nlink == 0 ?
1111 FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1112 goto whole;
1113 return 0;
1114 }
1115
1116 /* Dump segments that have been written to. */
1117 if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1118 goto whole;
1119 if (vma->vm_file == NULL)
1120 return 0;
1121
1122 if (FILTER(MAPPED_PRIVATE))
1123 goto whole;
1124
1125 /*
1126 * If this is the beginning of an executable file mapping,
1127 * dump the first page to aid in determining what was mapped here.
1128 */
1129 if (FILTER(ELF_HEADERS) &&
1130 vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
1131 if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
1132 return PAGE_SIZE;
1133
1134 /*
1135 * ELF libraries aren't always executable.
1136 * We'll want to check whether the mapping starts with the ELF
1137 * magic, but not now - we're holding the mmap lock,
1138 * so copy_from_user() doesn't work here.
1139 * Use a placeholder instead, and fix it up later in
1140 * dump_vma_snapshot().
1141 */
1142 return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
1143 }
1144
1145 #undef FILTER
1146
1147 return 0;
1148
1149 whole:
1150 return vma->vm_end - vma->vm_start;
1151 }
1152
1153 /*
1154 * Helper function for iterating across a vma list. It ensures that the caller
1155 * will visit `gate_vma' prior to terminating the search.
1156 */
coredump_next_vma(struct vma_iterator * vmi,struct vm_area_struct * vma,struct vm_area_struct * gate_vma)1157 static struct vm_area_struct *coredump_next_vma(struct vma_iterator *vmi,
1158 struct vm_area_struct *vma,
1159 struct vm_area_struct *gate_vma)
1160 {
1161 if (gate_vma && (vma == gate_vma))
1162 return NULL;
1163
1164 vma = vma_next(vmi);
1165 if (vma)
1166 return vma;
1167 return gate_vma;
1168 }
1169
free_vma_snapshot(struct coredump_params * cprm)1170 static void free_vma_snapshot(struct coredump_params *cprm)
1171 {
1172 if (cprm->vma_meta) {
1173 int i;
1174 for (i = 0; i < cprm->vma_count; i++) {
1175 struct file *file = cprm->vma_meta[i].file;
1176 if (file)
1177 fput(file);
1178 }
1179 kvfree(cprm->vma_meta);
1180 cprm->vma_meta = NULL;
1181 }
1182 }
1183
cmp_vma_size(const void * vma_meta_lhs_ptr,const void * vma_meta_rhs_ptr)1184 static int cmp_vma_size(const void *vma_meta_lhs_ptr, const void *vma_meta_rhs_ptr)
1185 {
1186 const struct core_vma_metadata *vma_meta_lhs = vma_meta_lhs_ptr;
1187 const struct core_vma_metadata *vma_meta_rhs = vma_meta_rhs_ptr;
1188
1189 if (vma_meta_lhs->dump_size < vma_meta_rhs->dump_size)
1190 return -1;
1191 if (vma_meta_lhs->dump_size > vma_meta_rhs->dump_size)
1192 return 1;
1193 return 0;
1194 }
1195
1196 /*
1197 * Under the mmap_lock, take a snapshot of relevant information about the task's
1198 * VMAs.
1199 */
dump_vma_snapshot(struct coredump_params * cprm)1200 static bool dump_vma_snapshot(struct coredump_params *cprm)
1201 {
1202 struct vm_area_struct *gate_vma, *vma = NULL;
1203 struct mm_struct *mm = current->mm;
1204 VMA_ITERATOR(vmi, mm, 0);
1205 int i = 0;
1206
1207 /*
1208 * Once the stack expansion code is fixed to not change VMA bounds
1209 * under mmap_lock in read mode, this can be changed to take the
1210 * mmap_lock in read mode.
1211 */
1212 if (mmap_write_lock_killable(mm))
1213 return false;
1214
1215 cprm->vma_data_size = 0;
1216 gate_vma = get_gate_vma(mm);
1217 cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
1218
1219 cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
1220 if (!cprm->vma_meta) {
1221 mmap_write_unlock(mm);
1222 return false;
1223 }
1224
1225 while ((vma = coredump_next_vma(&vmi, vma, gate_vma)) != NULL) {
1226 struct core_vma_metadata *m = cprm->vma_meta + i;
1227
1228 m->start = vma->vm_start;
1229 m->end = vma->vm_end;
1230 m->flags = vma->vm_flags;
1231 m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1232 m->pgoff = vma->vm_pgoff;
1233 m->file = vma->vm_file;
1234 if (m->file)
1235 get_file(m->file);
1236 i++;
1237 }
1238
1239 mmap_write_unlock(mm);
1240
1241 for (i = 0; i < cprm->vma_count; i++) {
1242 struct core_vma_metadata *m = cprm->vma_meta + i;
1243
1244 if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
1245 char elfmag[SELFMAG];
1246
1247 if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
1248 memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
1249 m->dump_size = 0;
1250 } else {
1251 m->dump_size = PAGE_SIZE;
1252 }
1253 }
1254
1255 cprm->vma_data_size += m->dump_size;
1256 }
1257
1258 sort(cprm->vma_meta, cprm->vma_count, sizeof(*cprm->vma_meta),
1259 cmp_vma_size, NULL);
1260
1261 return true;
1262 }
1263