blob: 00a900a51a8b6665a790a7e7ec38450edaa70772
1 | #include <linux/slab.h> |
2 | #include <linux/file.h> |
3 | #include <linux/fdtable.h> |
4 | #include <linux/freezer.h> |
5 | #include <linux/mm.h> |
6 | #include <linux/stat.h> |
7 | #include <linux/fcntl.h> |
8 | #include <linux/swap.h> |
9 | #include <linux/string.h> |
10 | #include <linux/init.h> |
11 | #include <linux/pagemap.h> |
12 | #include <linux/perf_event.h> |
13 | #include <linux/highmem.h> |
14 | #include <linux/spinlock.h> |
15 | #include <linux/key.h> |
16 | #include <linux/personality.h> |
17 | #include <linux/binfmts.h> |
18 | #include <linux/coredump.h> |
19 | #include <linux/utsname.h> |
20 | #include <linux/pid_namespace.h> |
21 | #include <linux/module.h> |
22 | #include <linux/namei.h> |
23 | #include <linux/mount.h> |
24 | #include <linux/security.h> |
25 | #include <linux/syscalls.h> |
26 | #include <linux/tsacct_kern.h> |
27 | #include <linux/cn_proc.h> |
28 | #include <linux/audit.h> |
29 | #include <linux/tracehook.h> |
30 | #include <linux/kmod.h> |
31 | #include <linux/fsnotify.h> |
32 | #include <linux/fs_struct.h> |
33 | #include <linux/pipe_fs_i.h> |
34 | #include <linux/oom.h> |
35 | #include <linux/compat.h> |
36 | #include <linux/sched.h> |
37 | #include <linux/fs.h> |
38 | #include <linux/path.h> |
39 | #include <linux/timekeeping.h> |
40 | |
41 | #include <asm/uaccess.h> |
42 | #include <asm/mmu_context.h> |
43 | #include <asm/tlb.h> |
44 | #include <asm/exec.h> |
45 | |
46 | #include <trace/events/task.h> |
47 | #include "internal.h" |
48 | |
49 | #include <trace/events/sched.h> |
50 | |
51 | int core_uses_pid; |
52 | unsigned int core_pipe_limit; |
53 | char core_pattern[CORENAME_MAX_SIZE] = "core"; |
54 | static int core_name_size = CORENAME_MAX_SIZE; |
55 | |
56 | struct core_name { |
57 | char *corename; |
58 | int used, size; |
59 | }; |
60 | |
61 | /* The maximal length of core_pattern is also specified in sysctl.c */ |
62 | |
63 | static int expand_corename(struct core_name *cn, int size) |
64 | { |
65 | char *corename = krealloc(cn->corename, size, GFP_KERNEL); |
66 | |
67 | if (!corename) |
68 | return -ENOMEM; |
69 | |
70 | if (size > core_name_size) /* racy but harmless */ |
71 | core_name_size = size; |
72 | |
73 | cn->size = ksize(corename); |
74 | cn->corename = corename; |
75 | return 0; |
76 | } |
77 | |
78 | static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt, |
79 | va_list arg) |
80 | { |
81 | int free, need; |
82 | va_list arg_copy; |
83 | |
84 | again: |
85 | free = cn->size - cn->used; |
86 | |
87 | va_copy(arg_copy, arg); |
88 | need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy); |
89 | va_end(arg_copy); |
90 | |
91 | if (need < free) { |
92 | cn->used += need; |
93 | return 0; |
94 | } |
95 | |
96 | if (!expand_corename(cn, cn->size + need - free + 1)) |
97 | goto again; |
98 | |
99 | return -ENOMEM; |
100 | } |
101 | |
102 | static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...) |
103 | { |
104 | va_list arg; |
105 | int ret; |
106 | |
107 | va_start(arg, fmt); |
108 | ret = cn_vprintf(cn, fmt, arg); |
109 | va_end(arg); |
110 | |
111 | return ret; |
112 | } |
113 | |
114 | static __printf(2, 3) |
115 | int cn_esc_printf(struct core_name *cn, const char *fmt, ...) |
116 | { |
117 | int cur = cn->used; |
118 | va_list arg; |
119 | int ret; |
120 | |
121 | va_start(arg, fmt); |
122 | ret = cn_vprintf(cn, fmt, arg); |
123 | va_end(arg); |
124 | |
125 | if (ret == 0) { |
126 | /* |
127 | * Ensure that this coredump name component can't cause the |
128 | * resulting corefile path to consist of a ".." or ".". |
129 | */ |
130 | if ((cn->used - cur == 1 && cn->corename[cur] == '.') || |
131 | (cn->used - cur == 2 && cn->corename[cur] == '.' |
132 | && cn->corename[cur+1] == '.')) |
133 | cn->corename[cur] = '!'; |
134 | |
135 | /* |
136 | * Empty names are fishy and could be used to create a "//" in a |
137 | * corefile name, causing the coredump to happen one directory |
138 | * level too high. Enforce that all components of the core |
139 | * pattern are at least one character long. |
140 | */ |
141 | if (cn->used == cur) |
142 | ret = cn_printf(cn, "!"); |
143 | } |
144 | |
145 | for (; cur < cn->used; ++cur) { |
146 | if (cn->corename[cur] == '/') |
147 | cn->corename[cur] = '!'; |
148 | } |
149 | return ret; |
150 | } |
151 | |
152 | static int cn_print_exe_file(struct core_name *cn) |
153 | { |
154 | struct file *exe_file; |
155 | char *pathbuf, *path; |
156 | int ret; |
157 | |
158 | exe_file = get_mm_exe_file(current->mm); |
159 | if (!exe_file) |
160 | return cn_esc_printf(cn, "%s (path unknown)", current->comm); |
161 | |
162 | pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY); |
163 | if (!pathbuf) { |
164 | ret = -ENOMEM; |
165 | goto put_exe_file; |
166 | } |
167 | |
168 | path = file_path(exe_file, pathbuf, PATH_MAX); |
169 | if (IS_ERR(path)) { |
170 | ret = PTR_ERR(path); |
171 | goto free_buf; |
172 | } |
173 | |
174 | ret = cn_esc_printf(cn, "%s", path); |
175 | |
176 | free_buf: |
177 | kfree(pathbuf); |
178 | put_exe_file: |
179 | fput(exe_file); |
180 | return ret; |
181 | } |
182 | |
183 | /* format_corename will inspect the pattern parameter, and output a |
184 | * name into corename, which must have space for at least |
185 | * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator. |
186 | */ |
187 | static int format_corename(struct core_name *cn, struct coredump_params *cprm) |
188 | { |
189 | const struct cred *cred = current_cred(); |
190 | const char *pat_ptr = core_pattern; |
191 | int ispipe = (*pat_ptr == '|'); |
192 | int pid_in_pattern = 0; |
193 | int err = 0; |
194 | |
195 | cn->used = 0; |
196 | cn->corename = NULL; |
197 | if (expand_corename(cn, core_name_size)) |
198 | return -ENOMEM; |
199 | cn->corename[0] = '\0'; |
200 | |
201 | if (ispipe) |
202 | ++pat_ptr; |
203 | |
204 | /* Repeat as long as we have more pattern to process and more output |
205 | space */ |
206 | while (*pat_ptr) { |
207 | if (*pat_ptr != '%') { |
208 | err = cn_printf(cn, "%c", *pat_ptr++); |
209 | } else { |
210 | switch (*++pat_ptr) { |
211 | /* single % at the end, drop that */ |
212 | case 0: |
213 | goto out; |
214 | /* Double percent, output one percent */ |
215 | case '%': |
216 | err = cn_printf(cn, "%c", '%'); |
217 | break; |
218 | /* pid */ |
219 | case 'p': |
220 | pid_in_pattern = 1; |
221 | err = cn_printf(cn, "%d", |
222 | task_tgid_vnr(current)); |
223 | break; |
224 | /* global pid */ |
225 | case 'P': |
226 | err = cn_printf(cn, "%d", |
227 | task_tgid_nr(current)); |
228 | break; |
229 | case 'i': |
230 | err = cn_printf(cn, "%d", |
231 | task_pid_vnr(current)); |
232 | break; |
233 | case 'I': |
234 | err = cn_printf(cn, "%d", |
235 | task_pid_nr(current)); |
236 | break; |
237 | /* uid */ |
238 | case 'u': |
239 | err = cn_printf(cn, "%u", |
240 | from_kuid(&init_user_ns, |
241 | cred->uid)); |
242 | break; |
243 | /* gid */ |
244 | case 'g': |
245 | err = cn_printf(cn, "%u", |
246 | from_kgid(&init_user_ns, |
247 | cred->gid)); |
248 | break; |
249 | case 'd': |
250 | err = cn_printf(cn, "%d", |
251 | __get_dumpable(cprm->mm_flags)); |
252 | break; |
253 | /* signal that caused the coredump */ |
254 | case 's': |
255 | err = cn_printf(cn, "%d", |
256 | cprm->siginfo->si_signo); |
257 | break; |
258 | /* UNIX time of coredump */ |
259 | case 't': { |
260 | time64_t time; |
261 | |
262 | time = ktime_get_real_seconds(); |
263 | err = cn_printf(cn, "%lld", time); |
264 | break; |
265 | } |
266 | /* hostname */ |
267 | case 'h': |
268 | down_read(&uts_sem); |
269 | err = cn_esc_printf(cn, "%s", |
270 | utsname()->nodename); |
271 | up_read(&uts_sem); |
272 | break; |
273 | /* executable */ |
274 | case 'e': |
275 | err = cn_esc_printf(cn, "%s", current->comm); |
276 | break; |
277 | case 'E': |
278 | err = cn_print_exe_file(cn); |
279 | break; |
280 | /* core limit size */ |
281 | case 'c': |
282 | err = cn_printf(cn, "%lu", |
283 | rlimit(RLIMIT_CORE)); |
284 | break; |
285 | default: |
286 | break; |
287 | } |
288 | ++pat_ptr; |
289 | } |
290 | |
291 | if (err) |
292 | return err; |
293 | } |
294 | |
295 | out: |
296 | /* Backward compatibility with core_uses_pid: |
297 | * |
298 | * If core_pattern does not include a %p (as is the default) |
299 | * and core_uses_pid is set, then .%pid will be appended to |
300 | * the filename. Do not do this for piped commands. */ |
301 | if (!ispipe && !pid_in_pattern && core_uses_pid) { |
302 | err = cn_printf(cn, ".%d", task_tgid_vnr(current)); |
303 | if (err) |
304 | return err; |
305 | } |
306 | return ispipe; |
307 | } |
308 | |
309 | static int zap_process(struct task_struct *start, int exit_code, int flags) |
310 | { |
311 | struct task_struct *t; |
312 | int nr = 0; |
313 | |
314 | /* ignore all signals except SIGKILL, see prepare_signal() */ |
315 | start->signal->flags = SIGNAL_GROUP_COREDUMP | flags; |
316 | start->signal->group_exit_code = exit_code; |
317 | start->signal->group_stop_count = 0; |
318 | |
319 | for_each_thread(start, t) { |
320 | task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK); |
321 | if (t != current && t->mm) { |
322 | sigaddset(&t->pending.signal, SIGKILL); |
323 | signal_wake_up(t, 1); |
324 | nr++; |
325 | } |
326 | } |
327 | |
328 | return nr; |
329 | } |
330 | |
331 | static int zap_threads(struct task_struct *tsk, struct mm_struct *mm, |
332 | struct core_state *core_state, int exit_code) |
333 | { |
334 | struct task_struct *g, *p; |
335 | unsigned long flags; |
336 | int nr = -EAGAIN; |
337 | |
338 | spin_lock_irq(&tsk->sighand->siglock); |
339 | if (!signal_group_exit(tsk->signal)) { |
340 | mm->core_state = core_state; |
341 | tsk->signal->group_exit_task = tsk; |
342 | nr = zap_process(tsk, exit_code, 0); |
343 | clear_tsk_thread_flag(tsk, TIF_SIGPENDING); |
344 | } |
345 | spin_unlock_irq(&tsk->sighand->siglock); |
346 | if (unlikely(nr < 0)) |
347 | return nr; |
348 | |
349 | tsk->flags |= PF_DUMPCORE; |
350 | if (atomic_read(&mm->mm_users) == nr + 1) |
351 | goto done; |
352 | /* |
353 | * We should find and kill all tasks which use this mm, and we should |
354 | * count them correctly into ->nr_threads. We don't take tasklist |
355 | * lock, but this is safe wrt: |
356 | * |
357 | * fork: |
358 | * None of sub-threads can fork after zap_process(leader). All |
359 | * processes which were created before this point should be |
360 | * visible to zap_threads() because copy_process() adds the new |
361 | * process to the tail of init_task.tasks list, and lock/unlock |
362 | * of ->siglock provides a memory barrier. |
363 | * |
364 | * do_exit: |
365 | * The caller holds mm->mmap_sem. This means that the task which |
366 | * uses this mm can't pass exit_mm(), so it can't exit or clear |
367 | * its ->mm. |
368 | * |
369 | * de_thread: |
370 | * It does list_replace_rcu(&leader->tasks, ¤t->tasks), |
371 | * we must see either old or new leader, this does not matter. |
372 | * However, it can change p->sighand, so lock_task_sighand(p) |
373 | * must be used. Since p->mm != NULL and we hold ->mmap_sem |
374 | * it can't fail. |
375 | * |
376 | * Note also that "g" can be the old leader with ->mm == NULL |
377 | * and already unhashed and thus removed from ->thread_group. |
378 | * This is OK, __unhash_process()->list_del_rcu() does not |
379 | * clear the ->next pointer, we will find the new leader via |
380 | * next_thread(). |
381 | */ |
382 | rcu_read_lock(); |
383 | for_each_process(g) { |
384 | if (g == tsk->group_leader) |
385 | continue; |
386 | if (g->flags & PF_KTHREAD) |
387 | continue; |
388 | |
389 | for_each_thread(g, p) { |
390 | if (unlikely(!p->mm)) |
391 | continue; |
392 | if (unlikely(p->mm == mm)) { |
393 | lock_task_sighand(p, &flags); |
394 | nr += zap_process(p, exit_code, |
395 | SIGNAL_GROUP_EXIT); |
396 | unlock_task_sighand(p, &flags); |
397 | } |
398 | break; |
399 | } |
400 | } |
401 | rcu_read_unlock(); |
402 | done: |
403 | atomic_set(&core_state->nr_threads, nr); |
404 | return nr; |
405 | } |
406 | |
407 | static int coredump_wait(int exit_code, struct core_state *core_state) |
408 | { |
409 | struct task_struct *tsk = current; |
410 | struct mm_struct *mm = tsk->mm; |
411 | int core_waiters = -EBUSY; |
412 | |
413 | init_completion(&core_state->startup); |
414 | core_state->dumper.task = tsk; |
415 | core_state->dumper.next = NULL; |
416 | |
417 | if (down_write_killable(&mm->mmap_sem)) |
418 | return -EINTR; |
419 | |
420 | if (!mm->core_state) |
421 | core_waiters = zap_threads(tsk, mm, core_state, exit_code); |
422 | up_write(&mm->mmap_sem); |
423 | |
424 | if (core_waiters > 0) { |
425 | struct core_thread *ptr; |
426 | |
427 | freezer_do_not_count(); |
428 | wait_for_completion(&core_state->startup); |
429 | freezer_count(); |
430 | /* |
431 | * Wait for all the threads to become inactive, so that |
432 | * all the thread context (extended register state, like |
433 | * fpu etc) gets copied to the memory. |
434 | */ |
435 | ptr = core_state->dumper.next; |
436 | while (ptr != NULL) { |
437 | wait_task_inactive(ptr->task, 0); |
438 | ptr = ptr->next; |
439 | } |
440 | } |
441 | |
442 | return core_waiters; |
443 | } |
444 | |
445 | static void coredump_finish(struct mm_struct *mm, bool core_dumped) |
446 | { |
447 | struct core_thread *curr, *next; |
448 | struct task_struct *task; |
449 | |
450 | spin_lock_irq(¤t->sighand->siglock); |
451 | if (core_dumped && !__fatal_signal_pending(current)) |
452 | current->signal->group_exit_code |= 0x80; |
453 | current->signal->group_exit_task = NULL; |
454 | current->signal->flags = SIGNAL_GROUP_EXIT; |
455 | spin_unlock_irq(¤t->sighand->siglock); |
456 | |
457 | next = mm->core_state->dumper.next; |
458 | while ((curr = next) != NULL) { |
459 | next = curr->next; |
460 | task = curr->task; |
461 | /* |
462 | * see exit_mm(), curr->task must not see |
463 | * ->task == NULL before we read ->next. |
464 | */ |
465 | smp_mb(); |
466 | curr->task = NULL; |
467 | wake_up_process(task); |
468 | } |
469 | |
470 | mm->core_state = NULL; |
471 | } |
472 | |
473 | static bool dump_interrupted(void) |
474 | { |
475 | /* |
476 | * SIGKILL or freezing() interrupt the coredumping. Perhaps we |
477 | * can do try_to_freeze() and check __fatal_signal_pending(), |
478 | * but then we need to teach dump_write() to restart and clear |
479 | * TIF_SIGPENDING. |
480 | */ |
481 | return signal_pending(current); |
482 | } |
483 | |
484 | static void wait_for_dump_helpers(struct file *file) |
485 | { |
486 | struct pipe_inode_info *pipe = file->private_data; |
487 | |
488 | pipe_lock(pipe); |
489 | pipe->readers++; |
490 | pipe->writers--; |
491 | wake_up_interruptible_sync(&pipe->wait); |
492 | kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); |
493 | pipe_unlock(pipe); |
494 | |
495 | /* |
496 | * We actually want wait_event_freezable() but then we need |
497 | * to clear TIF_SIGPENDING and improve dump_interrupted(). |
498 | */ |
499 | wait_event_interruptible(pipe->wait, pipe->readers == 1); |
500 | |
501 | pipe_lock(pipe); |
502 | pipe->readers--; |
503 | pipe->writers++; |
504 | pipe_unlock(pipe); |
505 | } |
506 | |
507 | /* |
508 | * umh_pipe_setup |
509 | * helper function to customize the process used |
510 | * to collect the core in userspace. Specifically |
511 | * it sets up a pipe and installs it as fd 0 (stdin) |
512 | * for the process. Returns 0 on success, or |
513 | * PTR_ERR on failure. |
514 | * Note that it also sets the core limit to 1. This |
515 | * is a special value that we use to trap recursive |
516 | * core dumps |
517 | */ |
518 | static int umh_pipe_setup(struct subprocess_info *info, struct cred *new) |
519 | { |
520 | struct file *files[2]; |
521 | struct coredump_params *cp = (struct coredump_params *)info->data; |
522 | int err = create_pipe_files(files, 0); |
523 | if (err) |
524 | return err; |
525 | |
526 | cp->file = files[1]; |
527 | |
528 | err = replace_fd(0, files[0], 0); |
529 | fput(files[0]); |
530 | /* and disallow core files too */ |
531 | current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1}; |
532 | |
533 | return err; |
534 | } |
535 | |
536 | void do_coredump(const siginfo_t *siginfo) |
537 | { |
538 | struct core_state core_state; |
539 | struct core_name cn; |
540 | struct mm_struct *mm = current->mm; |
541 | struct linux_binfmt * binfmt; |
542 | const struct cred *old_cred; |
543 | struct cred *cred; |
544 | int retval = 0; |
545 | int ispipe; |
546 | struct files_struct *displaced; |
547 | /* require nonrelative corefile path and be extra careful */ |
548 | bool need_suid_safe = false; |
549 | bool core_dumped = false; |
550 | static atomic_t core_dump_count = ATOMIC_INIT(0); |
551 | struct coredump_params cprm = { |
552 | .siginfo = siginfo, |
553 | .regs = signal_pt_regs(), |
554 | .limit = rlimit(RLIMIT_CORE), |
555 | /* |
556 | * We must use the same mm->flags while dumping core to avoid |
557 | * inconsistency of bit flags, since this flag is not protected |
558 | * by any locks. |
559 | */ |
560 | .mm_flags = mm->flags, |
561 | }; |
562 | |
563 | audit_core_dumps(siginfo->si_signo); |
564 | |
565 | binfmt = mm->binfmt; |
566 | if (!binfmt || !binfmt->core_dump) |
567 | goto fail; |
568 | if (!__get_dumpable(cprm.mm_flags)) |
569 | goto fail; |
570 | |
571 | cred = prepare_creds(); |
572 | if (!cred) |
573 | goto fail; |
574 | /* |
575 | * We cannot trust fsuid as being the "true" uid of the process |
576 | * nor do we know its entire history. We only know it was tainted |
577 | * so we dump it as root in mode 2, and only into a controlled |
578 | * environment (pipe handler or fully qualified path). |
579 | */ |
580 | if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) { |
581 | /* Setuid core dump mode */ |
582 | cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */ |
583 | need_suid_safe = true; |
584 | } |
585 | |
586 | retval = coredump_wait(siginfo->si_signo, &core_state); |
587 | if (retval < 0) |
588 | goto fail_creds; |
589 | |
590 | old_cred = override_creds(cred); |
591 | |
592 | ispipe = format_corename(&cn, &cprm); |
593 | |
594 | if (ispipe) { |
595 | int dump_count; |
596 | char **helper_argv; |
597 | struct subprocess_info *sub_info; |
598 | |
599 | if (ispipe < 0) { |
600 | printk(KERN_WARNING "format_corename failed\n"); |
601 | printk(KERN_WARNING "Aborting core\n"); |
602 | goto fail_unlock; |
603 | } |
604 | |
605 | if (cprm.limit == 1) { |
606 | /* See umh_pipe_setup() which sets RLIMIT_CORE = 1. |
607 | * |
608 | * Normally core limits are irrelevant to pipes, since |
609 | * we're not writing to the file system, but we use |
610 | * cprm.limit of 1 here as a special value, this is a |
611 | * consistent way to catch recursive crashes. |
612 | * We can still crash if the core_pattern binary sets |
613 | * RLIM_CORE = !1, but it runs as root, and can do |
614 | * lots of stupid things. |
615 | * |
616 | * Note that we use task_tgid_vnr here to grab the pid |
617 | * of the process group leader. That way we get the |
618 | * right pid if a thread in a multi-threaded |
619 | * core_pattern process dies. |
620 | */ |
621 | printk(KERN_WARNING |
622 | "Process %d(%s) has RLIMIT_CORE set to 1\n", |
623 | task_tgid_vnr(current), current->comm); |
624 | printk(KERN_WARNING "Aborting core\n"); |
625 | goto fail_unlock; |
626 | } |
627 | cprm.limit = RLIM_INFINITY; |
628 | |
629 | dump_count = atomic_inc_return(&core_dump_count); |
630 | if (core_pipe_limit && (core_pipe_limit < dump_count)) { |
631 | printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n", |
632 | task_tgid_vnr(current), current->comm); |
633 | printk(KERN_WARNING "Skipping core dump\n"); |
634 | goto fail_dropcount; |
635 | } |
636 | |
637 | helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL); |
638 | if (!helper_argv) { |
639 | printk(KERN_WARNING "%s failed to allocate memory\n", |
640 | __func__); |
641 | goto fail_dropcount; |
642 | } |
643 | |
644 | retval = -ENOMEM; |
645 | sub_info = call_usermodehelper_setup(helper_argv[0], |
646 | helper_argv, NULL, GFP_KERNEL, |
647 | umh_pipe_setup, NULL, &cprm); |
648 | if (sub_info) |
649 | retval = call_usermodehelper_exec(sub_info, |
650 | UMH_WAIT_EXEC); |
651 | |
652 | argv_free(helper_argv); |
653 | if (retval) { |
654 | printk(KERN_INFO "Core dump to |%s pipe failed\n", |
655 | cn.corename); |
656 | goto close_fail; |
657 | } |
658 | } else { |
659 | struct inode *inode; |
660 | int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW | |
661 | O_LARGEFILE | O_EXCL; |
662 | |
663 | if (cprm.limit < binfmt->min_coredump) |
664 | goto fail_unlock; |
665 | |
666 | if (need_suid_safe && cn.corename[0] != '/') { |
667 | printk(KERN_WARNING "Pid %d(%s) can only dump core "\ |
668 | "to fully qualified path!\n", |
669 | task_tgid_vnr(current), current->comm); |
670 | printk(KERN_WARNING "Skipping core dump\n"); |
671 | goto fail_unlock; |
672 | } |
673 | |
674 | /* |
675 | * Unlink the file if it exists unless this is a SUID |
676 | * binary - in that case, we're running around with root |
677 | * privs and don't want to unlink another user's coredump. |
678 | */ |
679 | if (!need_suid_safe) { |
680 | mm_segment_t old_fs; |
681 | |
682 | old_fs = get_fs(); |
683 | set_fs(KERNEL_DS); |
684 | /* |
685 | * If it doesn't exist, that's fine. If there's some |
686 | * other problem, we'll catch it at the filp_open(). |
687 | */ |
688 | (void) sys_unlink((const char __user *)cn.corename); |
689 | set_fs(old_fs); |
690 | } |
691 | |
692 | /* |
693 | * There is a race between unlinking and creating the |
694 | * file, but if that causes an EEXIST here, that's |
695 | * fine - another process raced with us while creating |
696 | * the corefile, and the other process won. To userspace, |
697 | * what matters is that at least one of the two processes |
698 | * writes its coredump successfully, not which one. |
699 | */ |
700 | if (need_suid_safe) { |
701 | /* |
702 | * Using user namespaces, normal user tasks can change |
703 | * their current->fs->root to point to arbitrary |
704 | * directories. Since the intention of the "only dump |
705 | * with a fully qualified path" rule is to control where |
706 | * coredumps may be placed using root privileges, |
707 | * current->fs->root must not be used. Instead, use the |
708 | * root directory of init_task. |
709 | */ |
710 | struct path root; |
711 | |
712 | task_lock(&init_task); |
713 | get_fs_root(init_task.fs, &root); |
714 | task_unlock(&init_task); |
715 | cprm.file = file_open_root(root.dentry, root.mnt, |
716 | cn.corename, open_flags, 0600); |
717 | path_put(&root); |
718 | } else { |
719 | cprm.file = filp_open(cn.corename, open_flags, 0600); |
720 | } |
721 | if (IS_ERR(cprm.file)) |
722 | goto fail_unlock; |
723 | |
724 | inode = file_inode(cprm.file); |
725 | if (inode->i_nlink > 1) |
726 | goto close_fail; |
727 | if (d_unhashed(cprm.file->f_path.dentry)) |
728 | goto close_fail; |
729 | /* |
730 | * AK: actually i see no reason to not allow this for named |
731 | * pipes etc, but keep the previous behaviour for now. |
732 | */ |
733 | if (!S_ISREG(inode->i_mode)) |
734 | goto close_fail; |
735 | /* |
736 | * Don't dump core if the filesystem changed owner or mode |
737 | * of the file during file creation. This is an issue when |
738 | * a process dumps core while its cwd is e.g. on a vfat |
739 | * filesystem. |
740 | */ |
741 | if (!uid_eq(inode->i_uid, current_fsuid())) |
742 | goto close_fail; |
743 | if ((inode->i_mode & 0677) != 0600) |
744 | goto close_fail; |
745 | if (!(cprm.file->f_mode & FMODE_CAN_WRITE)) |
746 | goto close_fail; |
747 | if (do_truncate2(cprm.file->f_path.mnt, cprm.file->f_path.dentry, 0, 0, cprm.file)) |
748 | goto close_fail; |
749 | } |
750 | |
751 | /* get us an unshared descriptor table; almost always a no-op */ |
752 | retval = unshare_files(&displaced); |
753 | if (retval) |
754 | goto close_fail; |
755 | if (displaced) |
756 | put_files_struct(displaced); |
757 | if (!dump_interrupted()) { |
758 | file_start_write(cprm.file); |
759 | core_dumped = binfmt->core_dump(&cprm); |
760 | file_end_write(cprm.file); |
761 | } |
762 | if (ispipe && core_pipe_limit) |
763 | wait_for_dump_helpers(cprm.file); |
764 | close_fail: |
765 | if (cprm.file) |
766 | filp_close(cprm.file, NULL); |
767 | fail_dropcount: |
768 | if (ispipe) |
769 | atomic_dec(&core_dump_count); |
770 | fail_unlock: |
771 | kfree(cn.corename); |
772 | coredump_finish(mm, core_dumped); |
773 | revert_creds(old_cred); |
774 | fail_creds: |
775 | put_cred(cred); |
776 | fail: |
777 | return; |
778 | } |
779 | |
780 | /* |
781 | * Core dumping helper functions. These are the only things you should |
782 | * do on a core-file: use only these functions to write out all the |
783 | * necessary info. |
784 | */ |
785 | int dump_emit(struct coredump_params *cprm, const void *addr, int nr) |
786 | { |
787 | struct file *file = cprm->file; |
788 | loff_t pos = file->f_pos; |
789 | ssize_t n; |
790 | if (cprm->written + nr > cprm->limit) |
791 | return 0; |
792 | while (nr) { |
793 | if (dump_interrupted()) |
794 | return 0; |
795 | n = __kernel_write(file, addr, nr, &pos); |
796 | if (n <= 0) |
797 | return 0; |
798 | file->f_pos = pos; |
799 | cprm->written += n; |
800 | cprm->pos += n; |
801 | nr -= n; |
802 | } |
803 | return 1; |
804 | } |
805 | EXPORT_SYMBOL(dump_emit); |
806 | |
807 | int dump_skip(struct coredump_params *cprm, size_t nr) |
808 | { |
809 | static char zeroes[PAGE_SIZE]; |
810 | struct file *file = cprm->file; |
811 | if (file->f_op->llseek && file->f_op->llseek != no_llseek) { |
812 | if (dump_interrupted() || |
813 | file->f_op->llseek(file, nr, SEEK_CUR) < 0) |
814 | return 0; |
815 | cprm->pos += nr; |
816 | return 1; |
817 | } else { |
818 | while (nr > PAGE_SIZE) { |
819 | if (!dump_emit(cprm, zeroes, PAGE_SIZE)) |
820 | return 0; |
821 | nr -= PAGE_SIZE; |
822 | } |
823 | return dump_emit(cprm, zeroes, nr); |
824 | } |
825 | } |
826 | EXPORT_SYMBOL(dump_skip); |
827 | |
828 | int dump_align(struct coredump_params *cprm, int align) |
829 | { |
830 | unsigned mod = cprm->pos & (align - 1); |
831 | if (align & (align - 1)) |
832 | return 0; |
833 | return mod ? dump_skip(cprm, align - mod) : 1; |
834 | } |
835 | EXPORT_SYMBOL(dump_align); |
836 | |
837 | /* |
838 | * Ensures that file size is big enough to contain the current file |
839 | * postion. This prevents gdb from complaining about a truncated file |
840 | * if the last "write" to the file was dump_skip. |
841 | */ |
842 | void dump_truncate(struct coredump_params *cprm) |
843 | { |
844 | struct file *file = cprm->file; |
845 | loff_t offset; |
846 | |
847 | if (file->f_op->llseek && file->f_op->llseek != no_llseek) { |
848 | offset = file->f_op->llseek(file, 0, SEEK_CUR); |
849 | if (i_size_read(file->f_mapping->host) < offset) |
850 | do_truncate(file->f_path.dentry, offset, 0, file); |
851 | } |
852 | } |
853 | EXPORT_SYMBOL(dump_truncate); |
854 |