xref: /openbmc/linux/fs/coredump.c (revision 94cdda6b)
1 #include <linux/slab.h>
2 #include <linux/file.h>
3 #include <linux/fdtable.h>
4 #include <linux/mm.h>
5 #include <linux/stat.h>
6 #include <linux/fcntl.h>
7 #include <linux/swap.h>
8 #include <linux/string.h>
9 #include <linux/init.h>
10 #include <linux/pagemap.h>
11 #include <linux/perf_event.h>
12 #include <linux/highmem.h>
13 #include <linux/spinlock.h>
14 #include <linux/key.h>
15 #include <linux/personality.h>
16 #include <linux/binfmts.h>
17 #include <linux/coredump.h>
18 #include <linux/utsname.h>
19 #include <linux/pid_namespace.h>
20 #include <linux/module.h>
21 #include <linux/namei.h>
22 #include <linux/mount.h>
23 #include <linux/security.h>
24 #include <linux/syscalls.h>
25 #include <linux/tsacct_kern.h>
26 #include <linux/cn_proc.h>
27 #include <linux/audit.h>
28 #include <linux/tracehook.h>
29 #include <linux/kmod.h>
30 #include <linux/fsnotify.h>
31 #include <linux/fs_struct.h>
32 #include <linux/pipe_fs_i.h>
33 #include <linux/oom.h>
34 #include <linux/compat.h>
35 
36 #include <asm/uaccess.h>
37 #include <asm/mmu_context.h>
38 #include <asm/tlb.h>
39 #include <asm/exec.h>
40 
41 #include <trace/events/task.h>
42 #include "internal.h"
43 
44 #include <trace/events/sched.h>
45 
46 int core_uses_pid;
47 unsigned int core_pipe_limit;
48 char core_pattern[CORENAME_MAX_SIZE] = "core";
49 static int core_name_size = CORENAME_MAX_SIZE;
50 
51 struct core_name {
52 	char *corename;
53 	int used, size;
54 };
55 
56 /* The maximal length of core_pattern is also specified in sysctl.c */
57 
58 static int expand_corename(struct core_name *cn, int size)
59 {
60 	char *corename = krealloc(cn->corename, size, GFP_KERNEL);
61 
62 	if (!corename)
63 		return -ENOMEM;
64 
65 	if (size > core_name_size) /* racy but harmless */
66 		core_name_size = size;
67 
68 	cn->size = ksize(corename);
69 	cn->corename = corename;
70 	return 0;
71 }
72 
73 static int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg)
74 {
75 	int free, need;
76 	va_list arg_copy;
77 
78 again:
79 	free = cn->size - cn->used;
80 
81 	va_copy(arg_copy, arg);
82 	need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
83 	va_end(arg_copy);
84 
85 	if (need < free) {
86 		cn->used += need;
87 		return 0;
88 	}
89 
90 	if (!expand_corename(cn, cn->size + need - free + 1))
91 		goto again;
92 
93 	return -ENOMEM;
94 }
95 
96 static int cn_printf(struct core_name *cn, const char *fmt, ...)
97 {
98 	va_list arg;
99 	int ret;
100 
101 	va_start(arg, fmt);
102 	ret = cn_vprintf(cn, fmt, arg);
103 	va_end(arg);
104 
105 	return ret;
106 }
107 
108 static int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
109 {
110 	int cur = cn->used;
111 	va_list arg;
112 	int ret;
113 
114 	va_start(arg, fmt);
115 	ret = cn_vprintf(cn, fmt, arg);
116 	va_end(arg);
117 
118 	for (; cur < cn->used; ++cur) {
119 		if (cn->corename[cur] == '/')
120 			cn->corename[cur] = '!';
121 	}
122 	return ret;
123 }
124 
125 static int cn_print_exe_file(struct core_name *cn)
126 {
127 	struct file *exe_file;
128 	char *pathbuf, *path;
129 	int ret;
130 
131 	exe_file = get_mm_exe_file(current->mm);
132 	if (!exe_file)
133 		return cn_esc_printf(cn, "%s (path unknown)", current->comm);
134 
135 	pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
136 	if (!pathbuf) {
137 		ret = -ENOMEM;
138 		goto put_exe_file;
139 	}
140 
141 	path = d_path(&exe_file->f_path, pathbuf, PATH_MAX);
142 	if (IS_ERR(path)) {
143 		ret = PTR_ERR(path);
144 		goto free_buf;
145 	}
146 
147 	ret = cn_esc_printf(cn, "%s", path);
148 
149 free_buf:
150 	kfree(pathbuf);
151 put_exe_file:
152 	fput(exe_file);
153 	return ret;
154 }
155 
156 /* format_corename will inspect the pattern parameter, and output a
157  * name into corename, which must have space for at least
158  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
159  */
160 static int format_corename(struct core_name *cn, struct coredump_params *cprm)
161 {
162 	const struct cred *cred = current_cred();
163 	const char *pat_ptr = core_pattern;
164 	int ispipe = (*pat_ptr == '|');
165 	int pid_in_pattern = 0;
166 	int err = 0;
167 
168 	cn->used = 0;
169 	cn->corename = NULL;
170 	if (expand_corename(cn, core_name_size))
171 		return -ENOMEM;
172 	cn->corename[0] = '\0';
173 
174 	if (ispipe)
175 		++pat_ptr;
176 
177 	/* Repeat as long as we have more pattern to process and more output
178 	   space */
179 	while (*pat_ptr) {
180 		if (*pat_ptr != '%') {
181 			err = cn_printf(cn, "%c", *pat_ptr++);
182 		} else {
183 			switch (*++pat_ptr) {
184 			/* single % at the end, drop that */
185 			case 0:
186 				goto out;
187 			/* Double percent, output one percent */
188 			case '%':
189 				err = cn_printf(cn, "%c", '%');
190 				break;
191 			/* pid */
192 			case 'p':
193 				pid_in_pattern = 1;
194 				err = cn_printf(cn, "%d",
195 					      task_tgid_vnr(current));
196 				break;
197 			/* global pid */
198 			case 'P':
199 				err = cn_printf(cn, "%d",
200 					      task_tgid_nr(current));
201 				break;
202 			case 'i':
203 				err = cn_printf(cn, "%d",
204 					      task_pid_vnr(current));
205 				break;
206 			case 'I':
207 				err = cn_printf(cn, "%d",
208 					      task_pid_nr(current));
209 				break;
210 			/* uid */
211 			case 'u':
212 				err = cn_printf(cn, "%d", cred->uid);
213 				break;
214 			/* gid */
215 			case 'g':
216 				err = cn_printf(cn, "%d", cred->gid);
217 				break;
218 			case 'd':
219 				err = cn_printf(cn, "%d",
220 					__get_dumpable(cprm->mm_flags));
221 				break;
222 			/* signal that caused the coredump */
223 			case 's':
224 				err = cn_printf(cn, "%ld", cprm->siginfo->si_signo);
225 				break;
226 			/* UNIX time of coredump */
227 			case 't': {
228 				struct timeval tv;
229 				do_gettimeofday(&tv);
230 				err = cn_printf(cn, "%lu", tv.tv_sec);
231 				break;
232 			}
233 			/* hostname */
234 			case 'h':
235 				down_read(&uts_sem);
236 				err = cn_esc_printf(cn, "%s",
237 					      utsname()->nodename);
238 				up_read(&uts_sem);
239 				break;
240 			/* executable */
241 			case 'e':
242 				err = cn_esc_printf(cn, "%s", current->comm);
243 				break;
244 			case 'E':
245 				err = cn_print_exe_file(cn);
246 				break;
247 			/* core limit size */
248 			case 'c':
249 				err = cn_printf(cn, "%lu",
250 					      rlimit(RLIMIT_CORE));
251 				break;
252 			default:
253 				break;
254 			}
255 			++pat_ptr;
256 		}
257 
258 		if (err)
259 			return err;
260 	}
261 
262 out:
263 	/* Backward compatibility with core_uses_pid:
264 	 *
265 	 * If core_pattern does not include a %p (as is the default)
266 	 * and core_uses_pid is set, then .%pid will be appended to
267 	 * the filename. Do not do this for piped commands. */
268 	if (!ispipe && !pid_in_pattern && core_uses_pid) {
269 		err = cn_printf(cn, ".%d", task_tgid_vnr(current));
270 		if (err)
271 			return err;
272 	}
273 	return ispipe;
274 }
275 
276 static int zap_process(struct task_struct *start, int exit_code)
277 {
278 	struct task_struct *t;
279 	int nr = 0;
280 
281 	start->signal->group_exit_code = exit_code;
282 	start->signal->group_stop_count = 0;
283 
284 	t = start;
285 	do {
286 		task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
287 		if (t != current && t->mm) {
288 			sigaddset(&t->pending.signal, SIGKILL);
289 			signal_wake_up(t, 1);
290 			nr++;
291 		}
292 	} while_each_thread(start, t);
293 
294 	return nr;
295 }
296 
297 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
298 			struct core_state *core_state, int exit_code)
299 {
300 	struct task_struct *g, *p;
301 	unsigned long flags;
302 	int nr = -EAGAIN;
303 
304 	spin_lock_irq(&tsk->sighand->siglock);
305 	if (!signal_group_exit(tsk->signal)) {
306 		mm->core_state = core_state;
307 		nr = zap_process(tsk, exit_code);
308 		tsk->signal->group_exit_task = tsk;
309 		/* ignore all signals except SIGKILL, see prepare_signal() */
310 		tsk->signal->flags = SIGNAL_GROUP_COREDUMP;
311 		clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
312 	}
313 	spin_unlock_irq(&tsk->sighand->siglock);
314 	if (unlikely(nr < 0))
315 		return nr;
316 
317 	tsk->flags |= PF_DUMPCORE;
318 	if (atomic_read(&mm->mm_users) == nr + 1)
319 		goto done;
320 	/*
321 	 * We should find and kill all tasks which use this mm, and we should
322 	 * count them correctly into ->nr_threads. We don't take tasklist
323 	 * lock, but this is safe wrt:
324 	 *
325 	 * fork:
326 	 *	None of sub-threads can fork after zap_process(leader). All
327 	 *	processes which were created before this point should be
328 	 *	visible to zap_threads() because copy_process() adds the new
329 	 *	process to the tail of init_task.tasks list, and lock/unlock
330 	 *	of ->siglock provides a memory barrier.
331 	 *
332 	 * do_exit:
333 	 *	The caller holds mm->mmap_sem. This means that the task which
334 	 *	uses this mm can't pass exit_mm(), so it can't exit or clear
335 	 *	its ->mm.
336 	 *
337 	 * de_thread:
338 	 *	It does list_replace_rcu(&leader->tasks, &current->tasks),
339 	 *	we must see either old or new leader, this does not matter.
340 	 *	However, it can change p->sighand, so lock_task_sighand(p)
341 	 *	must be used. Since p->mm != NULL and we hold ->mmap_sem
342 	 *	it can't fail.
343 	 *
344 	 *	Note also that "g" can be the old leader with ->mm == NULL
345 	 *	and already unhashed and thus removed from ->thread_group.
346 	 *	This is OK, __unhash_process()->list_del_rcu() does not
347 	 *	clear the ->next pointer, we will find the new leader via
348 	 *	next_thread().
349 	 */
350 	rcu_read_lock();
351 	for_each_process(g) {
352 		if (g == tsk->group_leader)
353 			continue;
354 		if (g->flags & PF_KTHREAD)
355 			continue;
356 		p = g;
357 		do {
358 			if (p->mm) {
359 				if (unlikely(p->mm == mm)) {
360 					lock_task_sighand(p, &flags);
361 					nr += zap_process(p, exit_code);
362 					p->signal->flags = SIGNAL_GROUP_EXIT;
363 					unlock_task_sighand(p, &flags);
364 				}
365 				break;
366 			}
367 		} while_each_thread(g, p);
368 	}
369 	rcu_read_unlock();
370 done:
371 	atomic_set(&core_state->nr_threads, nr);
372 	return nr;
373 }
374 
375 static int coredump_wait(int exit_code, struct core_state *core_state)
376 {
377 	struct task_struct *tsk = current;
378 	struct mm_struct *mm = tsk->mm;
379 	int core_waiters = -EBUSY;
380 
381 	init_completion(&core_state->startup);
382 	core_state->dumper.task = tsk;
383 	core_state->dumper.next = NULL;
384 
385 	down_write(&mm->mmap_sem);
386 	if (!mm->core_state)
387 		core_waiters = zap_threads(tsk, mm, core_state, exit_code);
388 	up_write(&mm->mmap_sem);
389 
390 	if (core_waiters > 0) {
391 		struct core_thread *ptr;
392 
393 		wait_for_completion(&core_state->startup);
394 		/*
395 		 * Wait for all the threads to become inactive, so that
396 		 * all the thread context (extended register state, like
397 		 * fpu etc) gets copied to the memory.
398 		 */
399 		ptr = core_state->dumper.next;
400 		while (ptr != NULL) {
401 			wait_task_inactive(ptr->task, 0);
402 			ptr = ptr->next;
403 		}
404 	}
405 
406 	return core_waiters;
407 }
408 
409 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
410 {
411 	struct core_thread *curr, *next;
412 	struct task_struct *task;
413 
414 	spin_lock_irq(&current->sighand->siglock);
415 	if (core_dumped && !__fatal_signal_pending(current))
416 		current->signal->group_exit_code |= 0x80;
417 	current->signal->group_exit_task = NULL;
418 	current->signal->flags = SIGNAL_GROUP_EXIT;
419 	spin_unlock_irq(&current->sighand->siglock);
420 
421 	next = mm->core_state->dumper.next;
422 	while ((curr = next) != NULL) {
423 		next = curr->next;
424 		task = curr->task;
425 		/*
426 		 * see exit_mm(), curr->task must not see
427 		 * ->task == NULL before we read ->next.
428 		 */
429 		smp_mb();
430 		curr->task = NULL;
431 		wake_up_process(task);
432 	}
433 
434 	mm->core_state = NULL;
435 }
436 
437 static bool dump_interrupted(void)
438 {
439 	/*
440 	 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
441 	 * can do try_to_freeze() and check __fatal_signal_pending(),
442 	 * but then we need to teach dump_write() to restart and clear
443 	 * TIF_SIGPENDING.
444 	 */
445 	return signal_pending(current);
446 }
447 
448 static void wait_for_dump_helpers(struct file *file)
449 {
450 	struct pipe_inode_info *pipe = file->private_data;
451 
452 	pipe_lock(pipe);
453 	pipe->readers++;
454 	pipe->writers--;
455 	wake_up_interruptible_sync(&pipe->wait);
456 	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
457 	pipe_unlock(pipe);
458 
459 	/*
460 	 * We actually want wait_event_freezable() but then we need
461 	 * to clear TIF_SIGPENDING and improve dump_interrupted().
462 	 */
463 	wait_event_interruptible(pipe->wait, pipe->readers == 1);
464 
465 	pipe_lock(pipe);
466 	pipe->readers--;
467 	pipe->writers++;
468 	pipe_unlock(pipe);
469 }
470 
471 /*
472  * umh_pipe_setup
473  * helper function to customize the process used
474  * to collect the core in userspace.  Specifically
475  * it sets up a pipe and installs it as fd 0 (stdin)
476  * for the process.  Returns 0 on success, or
477  * PTR_ERR on failure.
478  * Note that it also sets the core limit to 1.  This
479  * is a special value that we use to trap recursive
480  * core dumps
481  */
482 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
483 {
484 	struct file *files[2];
485 	struct coredump_params *cp = (struct coredump_params *)info->data;
486 	int err = create_pipe_files(files, 0);
487 	if (err)
488 		return err;
489 
490 	cp->file = files[1];
491 
492 	err = replace_fd(0, files[0], 0);
493 	fput(files[0]);
494 	/* and disallow core files too */
495 	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
496 
497 	return err;
498 }
499 
500 void do_coredump(const siginfo_t *siginfo)
501 {
502 	struct core_state core_state;
503 	struct core_name cn;
504 	struct mm_struct *mm = current->mm;
505 	struct linux_binfmt * binfmt;
506 	const struct cred *old_cred;
507 	struct cred *cred;
508 	int retval = 0;
509 	int flag = 0;
510 	int ispipe;
511 	struct files_struct *displaced;
512 	bool need_nonrelative = false;
513 	bool core_dumped = false;
514 	static atomic_t core_dump_count = ATOMIC_INIT(0);
515 	struct coredump_params cprm = {
516 		.siginfo = siginfo,
517 		.regs = signal_pt_regs(),
518 		.limit = rlimit(RLIMIT_CORE),
519 		/*
520 		 * We must use the same mm->flags while dumping core to avoid
521 		 * inconsistency of bit flags, since this flag is not protected
522 		 * by any locks.
523 		 */
524 		.mm_flags = mm->flags,
525 	};
526 
527 	audit_core_dumps(siginfo->si_signo);
528 
529 	binfmt = mm->binfmt;
530 	if (!binfmt || !binfmt->core_dump)
531 		goto fail;
532 	if (!__get_dumpable(cprm.mm_flags))
533 		goto fail;
534 
535 	cred = prepare_creds();
536 	if (!cred)
537 		goto fail;
538 	/*
539 	 * We cannot trust fsuid as being the "true" uid of the process
540 	 * nor do we know its entire history. We only know it was tainted
541 	 * so we dump it as root in mode 2, and only into a controlled
542 	 * environment (pipe handler or fully qualified path).
543 	 */
544 	if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
545 		/* Setuid core dump mode */
546 		flag = O_EXCL;		/* Stop rewrite attacks */
547 		cred->fsuid = GLOBAL_ROOT_UID;	/* Dump root private */
548 		need_nonrelative = true;
549 	}
550 
551 	retval = coredump_wait(siginfo->si_signo, &core_state);
552 	if (retval < 0)
553 		goto fail_creds;
554 
555 	old_cred = override_creds(cred);
556 
557 	ispipe = format_corename(&cn, &cprm);
558 
559 	if (ispipe) {
560 		int dump_count;
561 		char **helper_argv;
562 		struct subprocess_info *sub_info;
563 
564 		if (ispipe < 0) {
565 			printk(KERN_WARNING "format_corename failed\n");
566 			printk(KERN_WARNING "Aborting core\n");
567 			goto fail_unlock;
568 		}
569 
570 		if (cprm.limit == 1) {
571 			/* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
572 			 *
573 			 * Normally core limits are irrelevant to pipes, since
574 			 * we're not writing to the file system, but we use
575 			 * cprm.limit of 1 here as a special value, this is a
576 			 * consistent way to catch recursive crashes.
577 			 * We can still crash if the core_pattern binary sets
578 			 * RLIM_CORE = !1, but it runs as root, and can do
579 			 * lots of stupid things.
580 			 *
581 			 * Note that we use task_tgid_vnr here to grab the pid
582 			 * of the process group leader.  That way we get the
583 			 * right pid if a thread in a multi-threaded
584 			 * core_pattern process dies.
585 			 */
586 			printk(KERN_WARNING
587 				"Process %d(%s) has RLIMIT_CORE set to 1\n",
588 				task_tgid_vnr(current), current->comm);
589 			printk(KERN_WARNING "Aborting core\n");
590 			goto fail_unlock;
591 		}
592 		cprm.limit = RLIM_INFINITY;
593 
594 		dump_count = atomic_inc_return(&core_dump_count);
595 		if (core_pipe_limit && (core_pipe_limit < dump_count)) {
596 			printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
597 			       task_tgid_vnr(current), current->comm);
598 			printk(KERN_WARNING "Skipping core dump\n");
599 			goto fail_dropcount;
600 		}
601 
602 		helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL);
603 		if (!helper_argv) {
604 			printk(KERN_WARNING "%s failed to allocate memory\n",
605 			       __func__);
606 			goto fail_dropcount;
607 		}
608 
609 		retval = -ENOMEM;
610 		sub_info = call_usermodehelper_setup(helper_argv[0],
611 						helper_argv, NULL, GFP_KERNEL,
612 						umh_pipe_setup, NULL, &cprm);
613 		if (sub_info)
614 			retval = call_usermodehelper_exec(sub_info,
615 							  UMH_WAIT_EXEC);
616 
617 		argv_free(helper_argv);
618 		if (retval) {
619 			printk(KERN_INFO "Core dump to |%s pipe failed\n",
620 			       cn.corename);
621 			goto close_fail;
622 		}
623 	} else {
624 		struct inode *inode;
625 
626 		if (cprm.limit < binfmt->min_coredump)
627 			goto fail_unlock;
628 
629 		if (need_nonrelative && cn.corename[0] != '/') {
630 			printk(KERN_WARNING "Pid %d(%s) can only dump core "\
631 				"to fully qualified path!\n",
632 				task_tgid_vnr(current), current->comm);
633 			printk(KERN_WARNING "Skipping core dump\n");
634 			goto fail_unlock;
635 		}
636 
637 		cprm.file = filp_open(cn.corename,
638 				 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
639 				 0600);
640 		if (IS_ERR(cprm.file))
641 			goto fail_unlock;
642 
643 		inode = file_inode(cprm.file);
644 		if (inode->i_nlink > 1)
645 			goto close_fail;
646 		if (d_unhashed(cprm.file->f_path.dentry))
647 			goto close_fail;
648 		/*
649 		 * AK: actually i see no reason to not allow this for named
650 		 * pipes etc, but keep the previous behaviour for now.
651 		 */
652 		if (!S_ISREG(inode->i_mode))
653 			goto close_fail;
654 		/*
655 		 * Dont allow local users get cute and trick others to coredump
656 		 * into their pre-created files.
657 		 */
658 		if (!uid_eq(inode->i_uid, current_fsuid()))
659 			goto close_fail;
660 		if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
661 			goto close_fail;
662 		if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
663 			goto close_fail;
664 	}
665 
666 	/* get us an unshared descriptor table; almost always a no-op */
667 	retval = unshare_files(&displaced);
668 	if (retval)
669 		goto close_fail;
670 	if (displaced)
671 		put_files_struct(displaced);
672 	if (!dump_interrupted()) {
673 		file_start_write(cprm.file);
674 		core_dumped = binfmt->core_dump(&cprm);
675 		file_end_write(cprm.file);
676 	}
677 	if (ispipe && core_pipe_limit)
678 		wait_for_dump_helpers(cprm.file);
679 close_fail:
680 	if (cprm.file)
681 		filp_close(cprm.file, NULL);
682 fail_dropcount:
683 	if (ispipe)
684 		atomic_dec(&core_dump_count);
685 fail_unlock:
686 	kfree(cn.corename);
687 	coredump_finish(mm, core_dumped);
688 	revert_creds(old_cred);
689 fail_creds:
690 	put_cred(cred);
691 fail:
692 	return;
693 }
694 
695 /*
696  * Core dumping helper functions.  These are the only things you should
697  * do on a core-file: use only these functions to write out all the
698  * necessary info.
699  */
700 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
701 {
702 	struct file *file = cprm->file;
703 	loff_t pos = file->f_pos;
704 	ssize_t n;
705 	if (cprm->written + nr > cprm->limit)
706 		return 0;
707 	while (nr) {
708 		if (dump_interrupted())
709 			return 0;
710 		n = __kernel_write(file, addr, nr, &pos);
711 		if (n <= 0)
712 			return 0;
713 		file->f_pos = pos;
714 		cprm->written += n;
715 		nr -= n;
716 	}
717 	return 1;
718 }
719 EXPORT_SYMBOL(dump_emit);
720 
721 int dump_skip(struct coredump_params *cprm, size_t nr)
722 {
723 	static char zeroes[PAGE_SIZE];
724 	struct file *file = cprm->file;
725 	if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
726 		if (cprm->written + nr > cprm->limit)
727 			return 0;
728 		if (dump_interrupted() ||
729 		    file->f_op->llseek(file, nr, SEEK_CUR) < 0)
730 			return 0;
731 		cprm->written += nr;
732 		return 1;
733 	} else {
734 		while (nr > PAGE_SIZE) {
735 			if (!dump_emit(cprm, zeroes, PAGE_SIZE))
736 				return 0;
737 			nr -= PAGE_SIZE;
738 		}
739 		return dump_emit(cprm, zeroes, nr);
740 	}
741 }
742 EXPORT_SYMBOL(dump_skip);
743 
744 int dump_align(struct coredump_params *cprm, int align)
745 {
746 	unsigned mod = cprm->written & (align - 1);
747 	if (align & (align - 1))
748 		return 0;
749 	return mod ? dump_skip(cprm, align - mod) : 1;
750 }
751 EXPORT_SYMBOL(dump_align);
752