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->flags & PF_POSTCOREDUMP)) {
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 core_state * core_state,int exit_code)372 static int zap_threads(struct task_struct *tsk,
373 struct core_state *core_state, int exit_code)
374 {
375 int nr = -EAGAIN;
376
377 spin_lock_irq(&tsk->sighand->siglock);
378 if (!signal_group_exit(tsk->signal)) {
379 tsk->signal->core_state = core_state;
380 tsk->signal->group_exit_task = tsk;
381 nr = zap_process(tsk, exit_code, 0);
382 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
383 tsk->flags |= PF_DUMPCORE;
384 atomic_set(&core_state->nr_threads, nr);
385 }
386 spin_unlock_irq(&tsk->sighand->siglock);
387 return nr;
388 }
389
coredump_wait(int exit_code,struct core_state * core_state)390 static int coredump_wait(int exit_code, struct core_state *core_state)
391 {
392 struct task_struct *tsk = current;
393 int core_waiters = -EBUSY;
394
395 init_completion(&core_state->startup);
396 core_state->dumper.task = tsk;
397 core_state->dumper.next = NULL;
398
399 core_waiters = zap_threads(tsk, core_state, exit_code);
400 if (core_waiters > 0) {
401 struct core_thread *ptr;
402
403 freezer_do_not_count();
404 wait_for_completion(&core_state->startup);
405 freezer_count();
406 /*
407 * Wait for all the threads to become inactive, so that
408 * all the thread context (extended register state, like
409 * fpu etc) gets copied to the memory.
410 */
411 ptr = core_state->dumper.next;
412 while (ptr != NULL) {
413 wait_task_inactive(ptr->task, 0);
414 ptr = ptr->next;
415 }
416 }
417
418 return core_waiters;
419 }
420
coredump_finish(bool core_dumped)421 static void coredump_finish(bool core_dumped)
422 {
423 struct core_thread *curr, *next;
424 struct task_struct *task;
425
426 spin_lock_irq(¤t->sighand->siglock);
427 if (core_dumped && !__fatal_signal_pending(current))
428 current->signal->group_exit_code |= 0x80;
429 current->signal->group_exit_task = NULL;
430 current->signal->flags = SIGNAL_GROUP_EXIT;
431 next = current->signal->core_state->dumper.next;
432 current->signal->core_state = NULL;
433 spin_unlock_irq(¤t->sighand->siglock);
434
435 while ((curr = next) != NULL) {
436 next = curr->next;
437 task = curr->task;
438 /*
439 * see coredump_task_exit(), curr->task must not see
440 * ->task == NULL before we read ->next.
441 */
442 smp_mb();
443 curr->task = NULL;
444 wake_up_process(task);
445 }
446 }
447
dump_interrupted(void)448 static bool dump_interrupted(void)
449 {
450 /*
451 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
452 * can do try_to_freeze() and check __fatal_signal_pending(),
453 * but then we need to teach dump_write() to restart and clear
454 * TIF_SIGPENDING.
455 */
456 return fatal_signal_pending(current) || freezing(current);
457 }
458
wait_for_dump_helpers(struct file * file)459 static void wait_for_dump_helpers(struct file *file)
460 {
461 struct pipe_inode_info *pipe = file->private_data;
462
463 pipe_lock(pipe);
464 pipe->readers++;
465 pipe->writers--;
466 wake_up_interruptible_sync(&pipe->rd_wait);
467 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
468 pipe_unlock(pipe);
469
470 /*
471 * We actually want wait_event_freezable() but then we need
472 * to clear TIF_SIGPENDING and improve dump_interrupted().
473 */
474 wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
475
476 pipe_lock(pipe);
477 pipe->readers--;
478 pipe->writers++;
479 pipe_unlock(pipe);
480 }
481
482 /*
483 * umh_pipe_setup
484 * helper function to customize the process used
485 * to collect the core in userspace. Specifically
486 * it sets up a pipe and installs it as fd 0 (stdin)
487 * for the process. Returns 0 on success, or
488 * PTR_ERR on failure.
489 * Note that it also sets the core limit to 1. This
490 * is a special value that we use to trap recursive
491 * core dumps
492 */
umh_pipe_setup(struct subprocess_info * info,struct cred * new)493 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
494 {
495 struct file *files[2];
496 struct coredump_params *cp = (struct coredump_params *)info->data;
497 int err = create_pipe_files(files, 0);
498 if (err)
499 return err;
500
501 cp->file = files[1];
502
503 err = replace_fd(0, files[0], 0);
504 fput(files[0]);
505 /* and disallow core files too */
506 current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
507
508 return err;
509 }
510
do_coredump(const kernel_siginfo_t * siginfo)511 void do_coredump(const kernel_siginfo_t *siginfo)
512 {
513 struct core_state core_state;
514 struct core_name cn;
515 struct mm_struct *mm = current->mm;
516 struct linux_binfmt * binfmt;
517 const struct cred *old_cred;
518 struct cred *cred;
519 int retval = 0;
520 int ispipe;
521 size_t *argv = NULL;
522 int argc = 0;
523 /* require nonrelative corefile path and be extra careful */
524 bool need_suid_safe = false;
525 bool core_dumped = false;
526 static atomic_t core_dump_count = ATOMIC_INIT(0);
527 struct coredump_params cprm = {
528 .siginfo = siginfo,
529 .regs = signal_pt_regs(),
530 .limit = rlimit(RLIMIT_CORE),
531 /*
532 * We must use the same mm->flags while dumping core to avoid
533 * inconsistency of bit flags, since this flag is not protected
534 * by any locks.
535 */
536 .mm_flags = mm->flags,
537 };
538
539 audit_core_dumps(siginfo->si_signo);
540
541 binfmt = mm->binfmt;
542 if (!binfmt || !binfmt->core_dump)
543 goto fail;
544 if (!__get_dumpable(cprm.mm_flags))
545 goto fail;
546
547 cred = prepare_creds();
548 if (!cred)
549 goto fail;
550 /*
551 * We cannot trust fsuid as being the "true" uid of the process
552 * nor do we know its entire history. We only know it was tainted
553 * so we dump it as root in mode 2, and only into a controlled
554 * environment (pipe handler or fully qualified path).
555 */
556 if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
557 /* Setuid core dump mode */
558 cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */
559 need_suid_safe = true;
560 }
561
562 retval = coredump_wait(siginfo->si_signo, &core_state);
563 if (retval < 0)
564 goto fail_creds;
565
566 old_cred = override_creds(cred);
567
568 ispipe = format_corename(&cn, &cprm, &argv, &argc);
569
570 if (ispipe) {
571 int argi;
572 int dump_count;
573 char **helper_argv;
574 struct subprocess_info *sub_info;
575
576 if (ispipe < 0) {
577 printk(KERN_WARNING "format_corename failed\n");
578 printk(KERN_WARNING "Aborting core\n");
579 goto fail_unlock;
580 }
581
582 if (cprm.limit == 1) {
583 /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
584 *
585 * Normally core limits are irrelevant to pipes, since
586 * we're not writing to the file system, but we use
587 * cprm.limit of 1 here as a special value, this is a
588 * consistent way to catch recursive crashes.
589 * We can still crash if the core_pattern binary sets
590 * RLIM_CORE = !1, but it runs as root, and can do
591 * lots of stupid things.
592 *
593 * Note that we use task_tgid_vnr here to grab the pid
594 * of the process group leader. That way we get the
595 * right pid if a thread in a multi-threaded
596 * core_pattern process dies.
597 */
598 printk(KERN_WARNING
599 "Process %d(%s) has RLIMIT_CORE set to 1\n",
600 task_tgid_vnr(current), current->comm);
601 printk(KERN_WARNING "Aborting core\n");
602 goto fail_unlock;
603 }
604 cprm.limit = RLIM_INFINITY;
605
606 dump_count = atomic_inc_return(&core_dump_count);
607 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
608 printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
609 task_tgid_vnr(current), current->comm);
610 printk(KERN_WARNING "Skipping core dump\n");
611 goto fail_dropcount;
612 }
613
614 helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
615 GFP_KERNEL);
616 if (!helper_argv) {
617 printk(KERN_WARNING "%s failed to allocate memory\n",
618 __func__);
619 goto fail_dropcount;
620 }
621 for (argi = 0; argi < argc; argi++)
622 helper_argv[argi] = cn.corename + argv[argi];
623 helper_argv[argi] = NULL;
624
625 retval = -ENOMEM;
626 sub_info = call_usermodehelper_setup(helper_argv[0],
627 helper_argv, NULL, GFP_KERNEL,
628 umh_pipe_setup, NULL, &cprm);
629 if (sub_info)
630 retval = call_usermodehelper_exec(sub_info,
631 UMH_WAIT_EXEC);
632
633 kfree(helper_argv);
634 if (retval) {
635 printk(KERN_INFO "Core dump to |%s pipe failed\n",
636 cn.corename);
637 goto close_fail;
638 }
639 } else {
640 struct user_namespace *mnt_userns;
641 struct inode *inode;
642 int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
643 O_LARGEFILE | O_EXCL;
644
645 if (cprm.limit < binfmt->min_coredump)
646 goto fail_unlock;
647
648 if (need_suid_safe && cn.corename[0] != '/') {
649 printk(KERN_WARNING "Pid %d(%s) can only dump core "\
650 "to fully qualified path!\n",
651 task_tgid_vnr(current), current->comm);
652 printk(KERN_WARNING "Skipping core dump\n");
653 goto fail_unlock;
654 }
655
656 /*
657 * Unlink the file if it exists unless this is a SUID
658 * binary - in that case, we're running around with root
659 * privs and don't want to unlink another user's coredump.
660 */
661 if (!need_suid_safe) {
662 /*
663 * If it doesn't exist, that's fine. If there's some
664 * other problem, we'll catch it at the filp_open().
665 */
666 do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
667 }
668
669 /*
670 * There is a race between unlinking and creating the
671 * file, but if that causes an EEXIST here, that's
672 * fine - another process raced with us while creating
673 * the corefile, and the other process won. To userspace,
674 * what matters is that at least one of the two processes
675 * writes its coredump successfully, not which one.
676 */
677 if (need_suid_safe) {
678 /*
679 * Using user namespaces, normal user tasks can change
680 * their current->fs->root to point to arbitrary
681 * directories. Since the intention of the "only dump
682 * with a fully qualified path" rule is to control where
683 * coredumps may be placed using root privileges,
684 * current->fs->root must not be used. Instead, use the
685 * root directory of init_task.
686 */
687 struct path root;
688
689 task_lock(&init_task);
690 get_fs_root(init_task.fs, &root);
691 task_unlock(&init_task);
692 cprm.file = file_open_root(&root, cn.corename,
693 open_flags, 0600);
694 path_put(&root);
695 } else {
696 cprm.file = filp_open(cn.corename, open_flags, 0600);
697 }
698 if (IS_ERR(cprm.file))
699 goto fail_unlock;
700
701 inode = file_inode(cprm.file);
702 if (inode->i_nlink > 1)
703 goto close_fail;
704 if (d_unhashed(cprm.file->f_path.dentry))
705 goto close_fail;
706 /*
707 * AK: actually i see no reason to not allow this for named
708 * pipes etc, but keep the previous behaviour for now.
709 */
710 if (!S_ISREG(inode->i_mode))
711 goto close_fail;
712 /*
713 * Don't dump core if the filesystem changed owner or mode
714 * of the file during file creation. This is an issue when
715 * a process dumps core while its cwd is e.g. on a vfat
716 * filesystem.
717 */
718 mnt_userns = file_mnt_user_ns(cprm.file);
719 if (!uid_eq(i_uid_into_mnt(mnt_userns, inode),
720 current_fsuid())) {
721 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n",
722 cn.corename);
723 goto close_fail;
724 }
725 if ((inode->i_mode & 0677) != 0600) {
726 pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n",
727 cn.corename);
728 goto close_fail;
729 }
730 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
731 goto close_fail;
732 if (do_truncate(mnt_userns, cprm.file->f_path.dentry,
733 0, 0, cprm.file))
734 goto close_fail;
735 }
736
737 /* get us an unshared descriptor table; almost always a no-op */
738 /* The cell spufs coredump code reads the file descriptor tables */
739 retval = unshare_files();
740 if (retval)
741 goto close_fail;
742 if (!dump_interrupted()) {
743 /*
744 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
745 * have this set to NULL.
746 */
747 if (!cprm.file) {
748 pr_info("Core dump to |%s disabled\n", cn.corename);
749 goto close_fail;
750 }
751 file_start_write(cprm.file);
752 core_dumped = binfmt->core_dump(&cprm);
753 /*
754 * Ensures that file size is big enough to contain the current
755 * file postion. This prevents gdb from complaining about
756 * a truncated file if the last "write" to the file was
757 * dump_skip.
758 */
759 if (cprm.to_skip) {
760 cprm.to_skip--;
761 dump_emit(&cprm, "", 1);
762 }
763 file_end_write(cprm.file);
764 }
765 if (ispipe && core_pipe_limit)
766 wait_for_dump_helpers(cprm.file);
767 close_fail:
768 if (cprm.file)
769 filp_close(cprm.file, NULL);
770 fail_dropcount:
771 if (ispipe)
772 atomic_dec(&core_dump_count);
773 fail_unlock:
774 kfree(argv);
775 kfree(cn.corename);
776 coredump_finish(core_dumped);
777 revert_creds(old_cred);
778 fail_creds:
779 put_cred(cred);
780 fail:
781 return;
782 }
783
784 /*
785 * Core dumping helper functions. These are the only things you should
786 * do on a core-file: use only these functions to write out all the
787 * necessary info.
788 */
__dump_emit(struct coredump_params * cprm,const void * addr,int nr)789 static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
790 {
791 struct file *file = cprm->file;
792 loff_t pos = file->f_pos;
793 ssize_t n;
794 if (cprm->written + nr > cprm->limit)
795 return 0;
796
797
798 if (dump_interrupted())
799 return 0;
800 n = __kernel_write(file, addr, nr, &pos);
801 if (n != nr)
802 return 0;
803 file->f_pos = pos;
804 cprm->written += n;
805 cprm->pos += n;
806
807 return 1;
808 }
809
__dump_skip(struct coredump_params * cprm,size_t nr)810 static int __dump_skip(struct coredump_params *cprm, size_t nr)
811 {
812 static char zeroes[PAGE_SIZE];
813 struct file *file = cprm->file;
814 if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
815 if (dump_interrupted() ||
816 file->f_op->llseek(file, nr, SEEK_CUR) < 0)
817 return 0;
818 cprm->pos += nr;
819 return 1;
820 } else {
821 while (nr > PAGE_SIZE) {
822 if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
823 return 0;
824 nr -= PAGE_SIZE;
825 }
826 return __dump_emit(cprm, zeroes, nr);
827 }
828 }
829
dump_emit(struct coredump_params * cprm,const void * addr,int nr)830 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
831 {
832 if (cprm->to_skip) {
833 if (!__dump_skip(cprm, cprm->to_skip))
834 return 0;
835 cprm->to_skip = 0;
836 }
837 return __dump_emit(cprm, addr, nr);
838 }
839 EXPORT_SYMBOL(dump_emit);
840
dump_skip_to(struct coredump_params * cprm,unsigned long pos)841 void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
842 {
843 cprm->to_skip = pos - cprm->pos;
844 }
845 EXPORT_SYMBOL(dump_skip_to);
846
dump_skip(struct coredump_params * cprm,size_t nr)847 void dump_skip(struct coredump_params *cprm, size_t nr)
848 {
849 cprm->to_skip += nr;
850 }
851 EXPORT_SYMBOL(dump_skip);
852
853 #ifdef CONFIG_ELF_CORE
dump_user_range(struct coredump_params * cprm,unsigned long start,unsigned long len)854 int dump_user_range(struct coredump_params *cprm, unsigned long start,
855 unsigned long len)
856 {
857 unsigned long addr;
858
859 for (addr = start; addr < start + len; addr += PAGE_SIZE) {
860 struct page *page;
861 int stop;
862
863 /*
864 * To avoid having to allocate page tables for virtual address
865 * ranges that have never been used yet, and also to make it
866 * easy to generate sparse core files, use a helper that returns
867 * NULL when encountering an empty page table entry that would
868 * otherwise have been filled with the zero page.
869 */
870 page = get_dump_page(addr);
871 if (page) {
872 void *kaddr = kmap_local_page(page);
873
874 stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
875 kunmap_local(kaddr);
876 put_page(page);
877 if (stop)
878 return 0;
879 } else {
880 dump_skip(cprm, PAGE_SIZE);
881 }
882 }
883 return 1;
884 }
885 #endif
886
dump_align(struct coredump_params * cprm,int align)887 int dump_align(struct coredump_params *cprm, int align)
888 {
889 unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
890 if (align & (align - 1))
891 return 0;
892 if (mod)
893 cprm->to_skip += align - mod;
894 return 1;
895 }
896 EXPORT_SYMBOL(dump_align);
897
898 /*
899 * The purpose of always_dump_vma() is to make sure that special kernel mappings
900 * that are useful for post-mortem analysis are included in every core dump.
901 * In that way we ensure that the core dump is fully interpretable later
902 * without matching up the same kernel and hardware config to see what PC values
903 * meant. These special mappings include - vDSO, vsyscall, and other
904 * architecture specific mappings
905 */
always_dump_vma(struct vm_area_struct * vma)906 static bool always_dump_vma(struct vm_area_struct *vma)
907 {
908 /* Any vsyscall mappings? */
909 if (vma == get_gate_vma(vma->vm_mm))
910 return true;
911
912 /*
913 * Assume that all vmas with a .name op should always be dumped.
914 * If this changes, a new vm_ops field can easily be added.
915 */
916 if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
917 return true;
918
919 /*
920 * arch_vma_name() returns non-NULL for special architecture mappings,
921 * such as vDSO sections.
922 */
923 if (arch_vma_name(vma))
924 return true;
925
926 return false;
927 }
928
929 /*
930 * Decide how much of @vma's contents should be included in a core dump.
931 */
vma_dump_size(struct vm_area_struct * vma,unsigned long mm_flags)932 static unsigned long vma_dump_size(struct vm_area_struct *vma,
933 unsigned long mm_flags)
934 {
935 #define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
936
937 /* always dump the vdso and vsyscall sections */
938 if (always_dump_vma(vma))
939 goto whole;
940
941 if (vma->vm_flags & VM_DONTDUMP)
942 return 0;
943
944 /* support for DAX */
945 if (vma_is_dax(vma)) {
946 if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
947 goto whole;
948 if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
949 goto whole;
950 return 0;
951 }
952
953 /* Hugetlb memory check */
954 if (is_vm_hugetlb_page(vma)) {
955 if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
956 goto whole;
957 if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
958 goto whole;
959 return 0;
960 }
961
962 /* Do not dump I/O mapped devices or special mappings */
963 if (vma->vm_flags & VM_IO)
964 return 0;
965
966 /* By default, dump shared memory if mapped from an anonymous file. */
967 if (vma->vm_flags & VM_SHARED) {
968 if (file_inode(vma->vm_file)->i_nlink == 0 ?
969 FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
970 goto whole;
971 return 0;
972 }
973
974 /* Dump segments that have been written to. */
975 if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
976 goto whole;
977 if (vma->vm_file == NULL)
978 return 0;
979
980 if (FILTER(MAPPED_PRIVATE))
981 goto whole;
982
983 /*
984 * If this is the beginning of an executable file mapping,
985 * dump the first page to aid in determining what was mapped here.
986 */
987 if (FILTER(ELF_HEADERS) &&
988 vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ) &&
989 (READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
990 return PAGE_SIZE;
991
992 #undef FILTER
993
994 return 0;
995
996 whole:
997 return vma->vm_end - vma->vm_start;
998 }
999
first_vma(struct task_struct * tsk,struct vm_area_struct * gate_vma)1000 static struct vm_area_struct *first_vma(struct task_struct *tsk,
1001 struct vm_area_struct *gate_vma)
1002 {
1003 struct vm_area_struct *ret = tsk->mm->mmap;
1004
1005 if (ret)
1006 return ret;
1007 return gate_vma;
1008 }
1009
1010 /*
1011 * Helper function for iterating across a vma list. It ensures that the caller
1012 * will visit `gate_vma' prior to terminating the search.
1013 */
next_vma(struct vm_area_struct * this_vma,struct vm_area_struct * gate_vma)1014 static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
1015 struct vm_area_struct *gate_vma)
1016 {
1017 struct vm_area_struct *ret;
1018
1019 ret = this_vma->vm_next;
1020 if (ret)
1021 return ret;
1022 if (this_vma == gate_vma)
1023 return NULL;
1024 return gate_vma;
1025 }
1026
1027 /*
1028 * Under the mmap_lock, take a snapshot of relevant information about the task's
1029 * VMAs.
1030 */
dump_vma_snapshot(struct coredump_params * cprm,int * vma_count,struct core_vma_metadata ** vma_meta,size_t * vma_data_size_ptr)1031 int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
1032 struct core_vma_metadata **vma_meta,
1033 size_t *vma_data_size_ptr)
1034 {
1035 struct vm_area_struct *vma, *gate_vma;
1036 struct mm_struct *mm = current->mm;
1037 int i;
1038 size_t vma_data_size = 0;
1039
1040 /*
1041 * Once the stack expansion code is fixed to not change VMA bounds
1042 * under mmap_lock in read mode, this can be changed to take the
1043 * mmap_lock in read mode.
1044 */
1045 if (mmap_write_lock_killable(mm))
1046 return -EINTR;
1047
1048 gate_vma = get_gate_vma(mm);
1049 *vma_count = mm->map_count + (gate_vma ? 1 : 0);
1050
1051 *vma_meta = kvmalloc_array(*vma_count, sizeof(**vma_meta), GFP_KERNEL);
1052 if (!*vma_meta) {
1053 mmap_write_unlock(mm);
1054 return -ENOMEM;
1055 }
1056
1057 for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
1058 vma = next_vma(vma, gate_vma), i++) {
1059 struct core_vma_metadata *m = (*vma_meta) + i;
1060
1061 m->start = vma->vm_start;
1062 m->end = vma->vm_end;
1063 m->flags = vma->vm_flags;
1064 m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1065
1066 vma_data_size += m->dump_size;
1067 }
1068
1069 mmap_write_unlock(mm);
1070
1071 if (WARN_ON(i != *vma_count)) {
1072 kvfree(*vma_meta);
1073 return -EFAULT;
1074 }
1075
1076 *vma_data_size_ptr = vma_data_size;
1077 return 0;
1078 }
1079