Line data Source code
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 :
69 0 : static int expand_corename(struct core_name *cn, int size)
70 : {
71 : char *corename;
72 :
73 0 : size = kmalloc_size_roundup(size);
74 0 : corename = krealloc(cn->corename, size, GFP_KERNEL);
75 :
76 0 : if (!corename)
77 : return -ENOMEM;
78 :
79 0 : if (size > core_name_size) /* racy but harmless */
80 0 : core_name_size = size;
81 :
82 0 : cn->size = size;
83 0 : cn->corename = corename;
84 0 : return 0;
85 : }
86 :
87 0 : 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 0 : free = cn->size - cn->used;
95 :
96 0 : va_copy(arg_copy, arg);
97 0 : need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
98 0 : va_end(arg_copy);
99 :
100 0 : if (need < free) {
101 0 : cn->used += need;
102 0 : return 0;
103 : }
104 :
105 0 : if (!expand_corename(cn, cn->size + need - free + 1))
106 : goto again;
107 :
108 : return -ENOMEM;
109 : }
110 :
111 0 : static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
112 : {
113 : va_list arg;
114 : int ret;
115 :
116 0 : va_start(arg, fmt);
117 0 : ret = cn_vprintf(cn, fmt, arg);
118 0 : va_end(arg);
119 :
120 0 : return ret;
121 : }
122 :
123 : static __printf(2, 3)
124 0 : int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
125 : {
126 0 : int cur = cn->used;
127 : va_list arg;
128 : int ret;
129 :
130 0 : va_start(arg, fmt);
131 0 : ret = cn_vprintf(cn, fmt, arg);
132 0 : va_end(arg);
133 :
134 0 : 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 0 : if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
140 0 : (cn->used - cur == 2 && cn->corename[cur] == '.'
141 0 : && cn->corename[cur+1] == '.'))
142 0 : 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 0 : if (cn->used == cur)
151 0 : ret = cn_printf(cn, "!");
152 : }
153 :
154 0 : for (; cur < cn->used; ++cur) {
155 0 : if (cn->corename[cur] == '/')
156 0 : cn->corename[cur] = '!';
157 : }
158 0 : return ret;
159 : }
160 :
161 0 : 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 0 : exe_file = get_mm_exe_file(current->mm);
168 0 : if (!exe_file)
169 0 : return cn_esc_printf(cn, "%s (path unknown)", current->comm);
170 :
171 0 : pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
172 0 : if (!pathbuf) {
173 : ret = -ENOMEM;
174 : goto put_exe_file;
175 : }
176 :
177 0 : path = file_path(exe_file, pathbuf, PATH_MAX);
178 0 : if (IS_ERR(path)) {
179 0 : ret = PTR_ERR(path);
180 0 : goto free_buf;
181 : }
182 :
183 0 : if (name_only) {
184 0 : ptr = strrchr(path, '/');
185 0 : if (ptr)
186 0 : path = ptr + 1;
187 : }
188 0 : ret = cn_esc_printf(cn, "%s", path);
189 :
190 : free_buf:
191 0 : kfree(pathbuf);
192 : put_exe_file:
193 0 : fput(exe_file);
194 0 : 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 : */
201 0 : static int format_corename(struct core_name *cn, struct coredump_params *cprm,
202 : size_t **argv, int *argc)
203 : {
204 0 : const struct cred *cred = current_cred();
205 0 : const char *pat_ptr = core_pattern;
206 0 : int ispipe = (*pat_ptr == '|');
207 0 : bool was_space = false;
208 0 : int pid_in_pattern = 0;
209 0 : int err = 0;
210 :
211 0 : cn->used = 0;
212 0 : cn->corename = NULL;
213 0 : if (expand_corename(cn, core_name_size))
214 : return -ENOMEM;
215 0 : cn->corename[0] = '\0';
216 :
217 0 : if (ispipe) {
218 0 : int argvs = sizeof(core_pattern) / 2;
219 0 : (*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
220 0 : if (!(*argv))
221 : return -ENOMEM;
222 0 : (*argv)[(*argc)++] = 0;
223 0 : ++pat_ptr;
224 0 : 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 0 : 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 0 : if (ispipe) {
236 0 : if (isspace(*pat_ptr)) {
237 0 : if (cn->used != 0)
238 0 : was_space = true;
239 0 : pat_ptr++;
240 0 : continue;
241 0 : } else if (was_space) {
242 0 : was_space = false;
243 0 : err = cn_printf(cn, "%c", '\0');
244 0 : if (err)
245 : return err;
246 0 : (*argv)[(*argc)++] = cn->used;
247 : }
248 : }
249 0 : if (*pat_ptr != '%') {
250 0 : err = cn_printf(cn, "%c", *pat_ptr++);
251 : } else {
252 0 : 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 0 : err = cn_printf(cn, "%c", '%');
259 0 : break;
260 : /* pid */
261 : case 'p':
262 0 : pid_in_pattern = 1;
263 0 : err = cn_printf(cn, "%d",
264 0 : task_tgid_vnr(current));
265 0 : break;
266 : /* global pid */
267 : case 'P':
268 0 : err = cn_printf(cn, "%d",
269 0 : task_tgid_nr(current));
270 0 : break;
271 : case 'i':
272 0 : err = cn_printf(cn, "%d",
273 0 : task_pid_vnr(current));
274 0 : break;
275 : case 'I':
276 0 : err = cn_printf(cn, "%d",
277 0 : task_pid_nr(current));
278 0 : break;
279 : /* uid */
280 : case 'u':
281 0 : err = cn_printf(cn, "%u",
282 : from_kuid(&init_user_ns,
283 : cred->uid));
284 0 : break;
285 : /* gid */
286 : case 'g':
287 0 : err = cn_printf(cn, "%u",
288 : from_kgid(&init_user_ns,
289 : cred->gid));
290 0 : break;
291 : case 'd':
292 0 : err = cn_printf(cn, "%d",
293 : __get_dumpable(cprm->mm_flags));
294 0 : break;
295 : /* signal that caused the coredump */
296 : case 's':
297 0 : err = cn_printf(cn, "%d",
298 0 : cprm->siginfo->si_signo);
299 0 : break;
300 : /* UNIX time of coredump */
301 : case 't': {
302 : time64_t time;
303 :
304 0 : time = ktime_get_real_seconds();
305 0 : err = cn_printf(cn, "%lld", time);
306 0 : break;
307 : }
308 : /* hostname */
309 : case 'h':
310 0 : down_read(&uts_sem);
311 0 : err = cn_esc_printf(cn, "%s",
312 0 : utsname()->nodename);
313 0 : up_read(&uts_sem);
314 0 : break;
315 : /* executable, could be changed by prctl PR_SET_NAME etc */
316 : case 'e':
317 0 : err = cn_esc_printf(cn, "%s", current->comm);
318 0 : break;
319 : /* file name of executable */
320 : case 'f':
321 0 : err = cn_print_exe_file(cn, true);
322 0 : break;
323 : case 'E':
324 0 : err = cn_print_exe_file(cn, false);
325 0 : break;
326 : /* core limit size */
327 : case 'c':
328 0 : err = cn_printf(cn, "%lu",
329 : rlimit(RLIMIT_CORE));
330 0 : break;
331 : /* CPU the task ran on */
332 : case 'C':
333 0 : err = cn_printf(cn, "%d", cprm->cpu);
334 0 : break;
335 : default:
336 : break;
337 : }
338 0 : ++pat_ptr;
339 : }
340 :
341 0 : 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 0 : if (!ispipe && !pid_in_pattern && core_uses_pid) {
352 0 : err = cn_printf(cn, ".%d", task_tgid_vnr(current));
353 0 : if (err)
354 : return err;
355 : }
356 : return ispipe;
357 : }
358 :
359 0 : static int zap_process(struct task_struct *start, int exit_code)
360 : {
361 : struct task_struct *t;
362 0 : int nr = 0;
363 :
364 : /* Allow SIGKILL, see prepare_signal() */
365 0 : start->signal->flags = SIGNAL_GROUP_EXIT;
366 0 : start->signal->group_exit_code = exit_code;
367 0 : start->signal->group_stop_count = 0;
368 :
369 0 : for_each_thread(start, t) {
370 0 : task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
371 0 : if (t != current && !(t->flags & PF_POSTCOREDUMP)) {
372 0 : sigaddset(&t->pending.signal, SIGKILL);
373 0 : signal_wake_up(t, 1);
374 0 : nr++;
375 : }
376 : }
377 :
378 0 : return nr;
379 : }
380 :
381 0 : static int zap_threads(struct task_struct *tsk,
382 : struct core_state *core_state, int exit_code)
383 : {
384 0 : struct signal_struct *signal = tsk->signal;
385 0 : int nr = -EAGAIN;
386 :
387 0 : spin_lock_irq(&tsk->sighand->siglock);
388 0 : if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) {
389 0 : signal->core_state = core_state;
390 0 : nr = zap_process(tsk, exit_code);
391 0 : clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
392 0 : tsk->flags |= PF_DUMPCORE;
393 0 : atomic_set(&core_state->nr_threads, nr);
394 : }
395 0 : spin_unlock_irq(&tsk->sighand->siglock);
396 0 : return nr;
397 : }
398 :
399 0 : static int coredump_wait(int exit_code, struct core_state *core_state)
400 : {
401 0 : struct task_struct *tsk = current;
402 0 : int core_waiters = -EBUSY;
403 :
404 0 : init_completion(&core_state->startup);
405 0 : core_state->dumper.task = tsk;
406 0 : core_state->dumper.next = NULL;
407 :
408 0 : core_waiters = zap_threads(tsk, core_state, exit_code);
409 0 : if (core_waiters > 0) {
410 : struct core_thread *ptr;
411 :
412 0 : 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 0 : ptr = core_state->dumper.next;
420 0 : while (ptr != NULL) {
421 0 : wait_task_inactive(ptr->task, TASK_ANY);
422 0 : ptr = ptr->next;
423 : }
424 : }
425 :
426 0 : return core_waiters;
427 : }
428 :
429 0 : static void coredump_finish(bool core_dumped)
430 : {
431 : struct core_thread *curr, *next;
432 : struct task_struct *task;
433 :
434 0 : spin_lock_irq(¤t->sighand->siglock);
435 0 : if (core_dumped && !__fatal_signal_pending(current))
436 0 : current->signal->group_exit_code |= 0x80;
437 0 : next = current->signal->core_state->dumper.next;
438 0 : current->signal->core_state = NULL;
439 0 : spin_unlock_irq(¤t->sighand->siglock);
440 :
441 0 : while ((curr = next) != NULL) {
442 0 : next = curr->next;
443 0 : task = curr->task;
444 : /*
445 : * see coredump_task_exit(), curr->task must not see
446 : * ->task == NULL before we read ->next.
447 : */
448 0 : smp_mb();
449 0 : curr->task = NULL;
450 0 : wake_up_process(task);
451 : }
452 0 : }
453 :
454 0 : 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 0 : return fatal_signal_pending(current) || freezing(current);
463 : }
464 :
465 0 : static void wait_for_dump_helpers(struct file *file)
466 : {
467 0 : struct pipe_inode_info *pipe = file->private_data;
468 :
469 0 : pipe_lock(pipe);
470 0 : pipe->readers++;
471 0 : pipe->writers--;
472 0 : wake_up_interruptible_sync(&pipe->rd_wait);
473 0 : kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
474 0 : 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 0 : wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
481 :
482 0 : pipe_lock(pipe);
483 0 : pipe->readers--;
484 0 : pipe->writers++;
485 0 : pipe_unlock(pipe);
486 0 : }
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 : */
499 0 : static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
500 : {
501 : struct file *files[2];
502 0 : struct coredump_params *cp = (struct coredump_params *)info->data;
503 0 : int err = create_pipe_files(files, 0);
504 0 : if (err)
505 : return err;
506 :
507 0 : cp->file = files[1];
508 :
509 0 : err = replace_fd(0, files[0], 0);
510 0 : fput(files[0]);
511 : /* and disallow core files too */
512 0 : current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
513 :
514 0 : return err;
515 : }
516 :
517 0 : void do_coredump(const kernel_siginfo_t *siginfo)
518 : {
519 : struct core_state core_state;
520 : struct core_name cn;
521 0 : struct mm_struct *mm = current->mm;
522 : struct linux_binfmt * binfmt;
523 : const struct cred *old_cred;
524 : struct cred *cred;
525 0 : int retval = 0;
526 : int ispipe;
527 0 : size_t *argv = NULL;
528 0 : int argc = 0;
529 : /* require nonrelative corefile path and be extra careful */
530 0 : bool need_suid_safe = false;
531 0 : bool core_dumped = false;
532 : static atomic_t core_dump_count = ATOMIC_INIT(0);
533 0 : struct coredump_params cprm = {
534 : .siginfo = siginfo,
535 0 : .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 0 : .mm_flags = mm->flags,
542 : .vma_meta = NULL,
543 : .cpu = raw_smp_processor_id(),
544 : };
545 :
546 0 : audit_core_dumps(siginfo->si_signo);
547 :
548 0 : binfmt = mm->binfmt;
549 0 : if (!binfmt || !binfmt->core_dump)
550 : goto fail;
551 0 : if (!__get_dumpable(cprm.mm_flags))
552 : goto fail;
553 :
554 0 : cred = prepare_creds();
555 0 : 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 0 : if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
564 : /* Setuid core dump mode */
565 0 : cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */
566 0 : need_suid_safe = true;
567 : }
568 :
569 0 : retval = coredump_wait(siginfo->si_signo, &core_state);
570 0 : if (retval < 0)
571 : goto fail_creds;
572 :
573 0 : old_cred = override_creds(cred);
574 :
575 0 : ispipe = format_corename(&cn, &cprm, &argv, &argc);
576 :
577 0 : if (ispipe) {
578 : int argi;
579 : int dump_count;
580 : char **helper_argv;
581 : struct subprocess_info *sub_info;
582 :
583 0 : if (ispipe < 0) {
584 0 : printk(KERN_WARNING "format_corename failed\n");
585 0 : printk(KERN_WARNING "Aborting core\n");
586 0 : goto fail_unlock;
587 : }
588 :
589 0 : 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 0 : printk(KERN_WARNING
606 : "Process %d(%s) has RLIMIT_CORE set to 1\n",
607 : task_tgid_vnr(current), current->comm);
608 0 : printk(KERN_WARNING "Aborting core\n");
609 0 : goto fail_unlock;
610 : }
611 0 : cprm.limit = RLIM_INFINITY;
612 :
613 0 : dump_count = atomic_inc_return(&core_dump_count);
614 0 : if (core_pipe_limit && (core_pipe_limit < dump_count)) {
615 0 : printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
616 : task_tgid_vnr(current), current->comm);
617 0 : printk(KERN_WARNING "Skipping core dump\n");
618 0 : goto fail_dropcount;
619 : }
620 :
621 0 : helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
622 : GFP_KERNEL);
623 0 : if (!helper_argv) {
624 0 : printk(KERN_WARNING "%s failed to allocate memory\n",
625 : __func__);
626 0 : goto fail_dropcount;
627 : }
628 0 : for (argi = 0; argi < argc; argi++)
629 0 : helper_argv[argi] = cn.corename + argv[argi];
630 0 : helper_argv[argi] = NULL;
631 :
632 0 : retval = -ENOMEM;
633 0 : sub_info = call_usermodehelper_setup(helper_argv[0],
634 : helper_argv, NULL, GFP_KERNEL,
635 : umh_pipe_setup, NULL, &cprm);
636 0 : if (sub_info)
637 0 : retval = call_usermodehelper_exec(sub_info,
638 : UMH_WAIT_EXEC);
639 :
640 0 : kfree(helper_argv);
641 0 : if (retval) {
642 0 : printk(KERN_INFO "Core dump to |%s pipe failed\n",
643 : cn.corename);
644 0 : goto close_fail;
645 : }
646 : } else {
647 : struct mnt_idmap *idmap;
648 : struct inode *inode;
649 0 : int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
650 : O_LARGEFILE | O_EXCL;
651 :
652 0 : if (cprm.limit < binfmt->min_coredump)
653 : goto fail_unlock;
654 :
655 0 : if (need_suid_safe && cn.corename[0] != '/') {
656 0 : printk(KERN_WARNING "Pid %d(%s) can only dump core "\
657 : "to fully qualified path!\n",
658 : task_tgid_vnr(current), current->comm);
659 0 : printk(KERN_WARNING "Skipping core dump\n");
660 0 : 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 0 : 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 0 : 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 0 : 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 0 : task_lock(&init_task);
697 0 : get_fs_root(init_task.fs, &root);
698 0 : task_unlock(&init_task);
699 0 : cprm.file = file_open_root(&root, cn.corename,
700 : open_flags, 0600);
701 0 : path_put(&root);
702 : } else {
703 0 : cprm.file = filp_open(cn.corename, open_flags, 0600);
704 : }
705 0 : if (IS_ERR(cprm.file))
706 : goto fail_unlock;
707 :
708 0 : inode = file_inode(cprm.file);
709 0 : if (inode->i_nlink > 1)
710 : goto close_fail;
711 0 : 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 0 : 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 0 : idmap = file_mnt_idmap(cprm.file);
726 0 : if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode),
727 0 : current_fsuid())) {
728 0 : pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n",
729 : cn.corename);
730 : goto close_fail;
731 : }
732 0 : if ((inode->i_mode & 0677) != 0600) {
733 0 : pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n",
734 : cn.corename);
735 : goto close_fail;
736 : }
737 0 : if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
738 : goto close_fail;
739 0 : 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 0 : retval = unshare_files();
747 0 : if (retval)
748 : goto close_fail;
749 0 : if (!dump_interrupted()) {
750 : /*
751 : * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
752 : * have this set to NULL.
753 : */
754 0 : if (!cprm.file) {
755 0 : pr_info("Core dump to |%s disabled\n", cn.corename);
756 0 : goto close_fail;
757 : }
758 0 : if (!dump_vma_snapshot(&cprm))
759 : goto close_fail;
760 :
761 0 : file_start_write(cprm.file);
762 0 : 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 0 : if (cprm.to_skip) {
770 0 : cprm.to_skip--;
771 0 : dump_emit(&cprm, "", 1);
772 : }
773 0 : file_end_write(cprm.file);
774 0 : free_vma_snapshot(&cprm);
775 : }
776 0 : if (ispipe && core_pipe_limit)
777 0 : wait_for_dump_helpers(cprm.file);
778 : close_fail:
779 0 : if (cprm.file)
780 0 : filp_close(cprm.file, NULL);
781 : fail_dropcount:
782 0 : if (ispipe)
783 : atomic_dec(&core_dump_count);
784 : fail_unlock:
785 0 : kfree(argv);
786 0 : kfree(cn.corename);
787 0 : coredump_finish(core_dumped);
788 0 : revert_creds(old_cred);
789 : fail_creds:
790 : put_cred(cred);
791 : fail:
792 0 : 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 : */
800 0 : static int __dump_emit(struct coredump_params *cprm, const void *addr, int nr)
801 : {
802 0 : struct file *file = cprm->file;
803 0 : loff_t pos = file->f_pos;
804 : ssize_t n;
805 0 : if (cprm->written + nr > cprm->limit)
806 : return 0;
807 :
808 :
809 0 : if (dump_interrupted())
810 : return 0;
811 0 : n = __kernel_write(file, addr, nr, &pos);
812 0 : if (n != nr)
813 : return 0;
814 0 : file->f_pos = pos;
815 0 : cprm->written += n;
816 0 : cprm->pos += n;
817 :
818 0 : return 1;
819 : }
820 :
821 0 : static int __dump_skip(struct coredump_params *cprm, size_t nr)
822 : {
823 : static char zeroes[PAGE_SIZE];
824 0 : struct file *file = cprm->file;
825 0 : if (file->f_mode & FMODE_LSEEK) {
826 0 : if (dump_interrupted() ||
827 0 : vfs_llseek(file, nr, SEEK_CUR) < 0)
828 : return 0;
829 0 : cprm->pos += nr;
830 0 : return 1;
831 : } else {
832 0 : while (nr > PAGE_SIZE) {
833 0 : if (!__dump_emit(cprm, zeroes, PAGE_SIZE))
834 : return 0;
835 0 : nr -= PAGE_SIZE;
836 : }
837 0 : return __dump_emit(cprm, zeroes, nr);
838 : }
839 : }
840 :
841 0 : int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
842 : {
843 0 : if (cprm->to_skip) {
844 0 : if (!__dump_skip(cprm, cprm->to_skip))
845 : return 0;
846 0 : cprm->to_skip = 0;
847 : }
848 0 : return __dump_emit(cprm, addr, nr);
849 : }
850 : EXPORT_SYMBOL(dump_emit);
851 :
852 0 : void dump_skip_to(struct coredump_params *cprm, unsigned long pos)
853 : {
854 0 : cprm->to_skip = pos - cprm->pos;
855 0 : }
856 : EXPORT_SYMBOL(dump_skip_to);
857 :
858 0 : void dump_skip(struct coredump_params *cprm, size_t nr)
859 : {
860 0 : cprm->to_skip += nr;
861 0 : }
862 : EXPORT_SYMBOL(dump_skip);
863 :
864 : #ifdef CONFIG_ELF_CORE
865 0 : static int dump_emit_page(struct coredump_params *cprm, struct page *page)
866 : {
867 : struct bio_vec bvec;
868 : struct iov_iter iter;
869 0 : struct file *file = cprm->file;
870 : loff_t pos;
871 : ssize_t n;
872 :
873 0 : if (cprm->to_skip) {
874 0 : if (!__dump_skip(cprm, cprm->to_skip))
875 : return 0;
876 0 : cprm->to_skip = 0;
877 : }
878 0 : if (cprm->written + PAGE_SIZE > cprm->limit)
879 : return 0;
880 0 : if (dump_interrupted())
881 : return 0;
882 0 : pos = file->f_pos;
883 0 : bvec_set_page(&bvec, page, PAGE_SIZE, 0);
884 0 : iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE);
885 0 : n = __kernel_write_iter(cprm->file, &iter, &pos);
886 0 : if (n != PAGE_SIZE)
887 : return 0;
888 0 : file->f_pos = pos;
889 0 : cprm->written += PAGE_SIZE;
890 0 : cprm->pos += PAGE_SIZE;
891 :
892 0 : return 1;
893 : }
894 :
895 0 : int dump_user_range(struct coredump_params *cprm, unsigned long start,
896 : unsigned long len)
897 : {
898 : unsigned long addr;
899 :
900 0 : 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 0 : page = get_dump_page(addr);
911 0 : if (page) {
912 0 : int stop = !dump_emit_page(cprm, page);
913 0 : put_page(page);
914 0 : if (stop)
915 : return 0;
916 : } else {
917 : dump_skip(cprm, PAGE_SIZE);
918 : }
919 : }
920 : return 1;
921 : }
922 : #endif
923 :
924 0 : int dump_align(struct coredump_params *cprm, int align)
925 : {
926 0 : unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1);
927 0 : if (align & (align - 1))
928 : return 0;
929 0 : if (mod)
930 0 : cprm->to_skip += align - mod;
931 : return 1;
932 : }
933 : EXPORT_SYMBOL(dump_align);
934 :
935 : #ifdef CONFIG_SYSCTL
936 :
937 0 : void validate_coredump_safety(void)
938 : {
939 0 : if (suid_dumpable == SUID_DUMP_ROOT &&
940 0 : core_pattern[0] != '/' && core_pattern[0] != '|') {
941 0 : 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 0 : }
948 :
949 0 : static int proc_dostring_coredump(struct ctl_table *table, int write,
950 : void *buffer, size_t *lenp, loff_t *ppos)
951 : {
952 0 : int error = proc_dostring(table, write, buffer, lenp, ppos);
953 :
954 0 : if (!error)
955 0 : validate_coredump_safety();
956 0 : 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 :
984 1 : static int __init init_fs_coredump_sysctls(void)
985 : {
986 1 : register_sysctl_init("kernel", coredump_sysctls);
987 1 : 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 : */
1000 0 : static bool always_dump_vma(struct vm_area_struct *vma)
1001 : {
1002 : /* Any vsyscall mappings? */
1003 0 : 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 0 : 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 0 : if (arch_vma_name(vma))
1018 : return true;
1019 :
1020 0 : 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 : */
1028 0 : 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 0 : if (always_dump_vma(vma))
1035 : goto whole;
1036 :
1037 0 : if (vma->vm_flags & VM_DONTDUMP)
1038 : return 0;
1039 :
1040 : /* support for DAX */
1041 0 : 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 0 : 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 0 : if (vma->vm_flags & VM_IO)
1060 : return 0;
1061 :
1062 : /* By default, dump shared memory if mapped from an anonymous file. */
1063 0 : if (vma->vm_flags & VM_SHARED) {
1064 0 : if (file_inode(vma->vm_file)->i_nlink == 0 ?
1065 0 : FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
1066 : goto whole;
1067 : return 0;
1068 : }
1069 :
1070 : /* Dump segments that have been written to. */
1071 0 : if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
1072 : goto whole;
1073 0 : if (vma->vm_file == NULL)
1074 : return 0;
1075 :
1076 0 : 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 0 : if (FILTER(ELF_HEADERS) &&
1084 0 : vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
1085 0 : 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 0 : return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
1097 : }
1098 :
1099 : #undef FILTER
1100 :
1101 : return 0;
1102 :
1103 : whole:
1104 0 : 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 : */
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 0 : vma = vma_next(vmi);
1119 0 : if (vma)
1120 : return vma;
1121 : return gate_vma;
1122 : }
1123 :
1124 0 : static void free_vma_snapshot(struct coredump_params *cprm)
1125 : {
1126 0 : if (cprm->vma_meta) {
1127 : int i;
1128 0 : for (i = 0; i < cprm->vma_count; i++) {
1129 0 : struct file *file = cprm->vma_meta[i].file;
1130 0 : if (file)
1131 0 : fput(file);
1132 : }
1133 0 : kvfree(cprm->vma_meta);
1134 0 : cprm->vma_meta = NULL;
1135 : }
1136 0 : }
1137 :
1138 : /*
1139 : * Under the mmap_lock, take a snapshot of relevant information about the task's
1140 : * VMAs.
1141 : */
1142 0 : static bool dump_vma_snapshot(struct coredump_params *cprm)
1143 : {
1144 0 : struct vm_area_struct *gate_vma, *vma = NULL;
1145 0 : struct mm_struct *mm = current->mm;
1146 0 : VMA_ITERATOR(vmi, mm, 0);
1147 0 : 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 0 : if (mmap_write_lock_killable(mm))
1155 : return false;
1156 :
1157 0 : cprm->vma_data_size = 0;
1158 0 : gate_vma = get_gate_vma(mm);
1159 0 : cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
1160 :
1161 0 : cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
1162 0 : if (!cprm->vma_meta) {
1163 0 : mmap_write_unlock(mm);
1164 0 : return false;
1165 : }
1166 :
1167 0 : while ((vma = coredump_next_vma(&vmi, vma, gate_vma)) != NULL) {
1168 0 : struct core_vma_metadata *m = cprm->vma_meta + i;
1169 :
1170 0 : m->start = vma->vm_start;
1171 0 : m->end = vma->vm_end;
1172 0 : m->flags = vma->vm_flags;
1173 0 : m->dump_size = vma_dump_size(vma, cprm->mm_flags);
1174 0 : m->pgoff = vma->vm_pgoff;
1175 0 : m->file = vma->vm_file;
1176 0 : if (m->file)
1177 0 : get_file(m->file);
1178 0 : i++;
1179 : }
1180 :
1181 0 : mmap_write_unlock(mm);
1182 :
1183 0 : for (i = 0; i < cprm->vma_count; i++) {
1184 0 : struct core_vma_metadata *m = cprm->vma_meta + i;
1185 :
1186 0 : if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
1187 : char elfmag[SELFMAG];
1188 :
1189 0 : if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
1190 0 : memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
1191 0 : m->dump_size = 0;
1192 : } else {
1193 0 : m->dump_size = PAGE_SIZE;
1194 : }
1195 : }
1196 :
1197 0 : cprm->vma_data_size += m->dump_size;
1198 : }
1199 :
1200 : return true;
1201 : }
|
