summaryrefslogtreecommitdiff
path: root/fs/coredump.c
blob: c66bb0572265c1490adbb48c6cf671dd711db517 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/mm.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/swap.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <linux/perf_event.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <linux/key.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/coredump.h>
#include <linux/utsname.h>
#include <linux/pid_namespace.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/audit.h>
#include <linux/tracehook.h>
#include <linux/kmod.h>
#include <linux/fsnotify.h>
#include <linux/fs_struct.h>
#include <linux/pipe_fs_i.h>
#include <linux/oom.h>
#include <linux/compat.h>

#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>
#include <asm/exec.h>

#include <trace/events/task.h>
#include "internal.h"

#include <trace/events/sched.h>

int core_uses_pid;
unsigned int core_pipe_limit;
char core_pattern[CORENAME_MAX_SIZE] = "core";
static int core_name_size = CORENAME_MAX_SIZE;

struct core_name {
	char *corename;
	int used, size;
};

/* The maximal length of core_pattern is also specified in sysctl.c */

static int expand_corename(struct core_name *cn, int size)
{
	char *corename = krealloc(cn->corename, size, GFP_KERNEL);

	if (!corename)
		return -ENOMEM;

	if (size > core_name_size) /* racy but harmless */
		core_name_size = size;

	cn->size = ksize(corename);
	cn->corename = corename;
	return 0;
}

static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
				     va_list arg)
{
	int free, need;
	va_list arg_copy;

again:
	free = cn->size - cn->used;

	va_copy(arg_copy, arg);
	need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
	va_end(arg_copy);

	if (need < free) {
		cn->used += need;
		return 0;
	}

	if (!expand_corename(cn, cn->size + need - free + 1))
		goto again;

	return -ENOMEM;
}

static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
{
	va_list arg;
	int ret;

	va_start(arg, fmt);
	ret = cn_vprintf(cn, fmt, arg);
	va_end(arg);

	return ret;
}

static __printf(2, 3)
int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
{
	int cur = cn->used;
	va_list arg;
	int ret;

	va_start(arg, fmt);
	ret = cn_vprintf(cn, fmt, arg);
	va_end(arg);

	for (; cur < cn->used; ++cur) {
		if (cn->corename[cur] == '/')
			cn->corename[cur] = '!';
	}
	return ret;
}

static int cn_print_exe_file(struct core_name *cn)
{
	struct file *exe_file;
	char *pathbuf, *path;
	int ret;

	exe_file = get_mm_exe_file(current->mm);
	if (!exe_file)
		return cn_esc_printf(cn, "%s (path unknown)", current->comm);

	pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
	if (!pathbuf) {
		ret = -ENOMEM;
		goto put_exe_file;
	}

	path = file_path(exe_file, pathbuf, PATH_MAX);
	if (IS_ERR(path)) {
		ret = PTR_ERR(path);
		goto free_buf;
	}

	ret = cn_esc_printf(cn, "%s", path);

free_buf:
	kfree(pathbuf);
put_exe_file:
	fput(exe_file);
	return ret;
}

/* format_corename will inspect the pattern parameter, and output a
 * name into corename, which must have space for at least
 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
 */
static int format_corename(struct core_name *cn, struct coredump_params *cprm)
{
	const struct cred *cred = current_cred();
	const char *pat_ptr = core_pattern;
	int ispipe = (*pat_ptr == '|');
	int pid_in_pattern = 0;
	int err = 0;

	cn->used = 0;
	cn->corename = NULL;
	if (expand_corename(cn, core_name_size))
		return -ENOMEM;
	cn->corename[0] = '\0';

	if (ispipe)
		++pat_ptr;

	/* Repeat as long as we have more pattern to process and more output
	   space */
	while (*pat_ptr) {
		if (*pat_ptr != '%') {
			err = cn_printf(cn, "%c", *pat_ptr++);
		} else {
			switch (*++pat_ptr) {
			/* single % at the end, drop that */
			case 0:
				goto out;
			/* Double percent, output one percent */
			case '%':
				err = cn_printf(cn, "%c", '%');
				break;
			/* pid */
			case 'p':
				pid_in_pattern = 1;
				err = cn_printf(cn, "%d",
					      task_tgid_vnr(current));
				break;
			/* global pid */
			case 'P':
				err = cn_printf(cn, "%d",
					      task_tgid_nr(current));
				break;
			case 'i':
				err = cn_printf(cn, "%d",
					      task_pid_vnr(current));
				break;
			case 'I':
				err = cn_printf(cn, "%d",
					      task_pid_nr(current));
				break;
			/* uid */
			case 'u':
				err = cn_printf(cn, "%u",
						from_kuid(&init_user_ns,
							  cred->uid));
				break;
			/* gid */
			case 'g':
				err = cn_printf(cn, "%u",
						from_kgid(&init_user_ns,
							  cred->gid));
				break;
			case 'd':
				err = cn_printf(cn, "%d",
					__get_dumpable(cprm->mm_flags));
				break;
			/* signal that caused the coredump */
			case 's':
				err = cn_printf(cn, "%d",
						cprm->siginfo->si_signo);
				break;
			/* UNIX time of coredump */
			case 't': {
				struct timeval tv;
				do_gettimeofday(&tv);
				err = cn_printf(cn, "%lu", tv.tv_sec);
				break;
			}
			/* hostname */
			case 'h':
				down_read(&uts_sem);
				err = cn_esc_printf(cn, "%s",
					      utsname()->nodename);
				up_read(&uts_sem);
				break;
			/* executable */
			case 'e':
				err = cn_esc_printf(cn, "%s", current->comm);
				break;
			case 'E':
				err = cn_print_exe_file(cn);
				break;
			/* core limit size */
			case 'c':
				err = cn_printf(cn, "%lu",
					      rlimit(RLIMIT_CORE));
				break;
			default:
				break;
			}
			++pat_ptr;
		}

		if (err)
			return err;
	}

out:
	/* Backward compatibility with core_uses_pid:
	 *
	 * If core_pattern does not include a %p (as is the default)
	 * and core_uses_pid is set, then .%pid will be appended to
	 * the filename. Do not do this for piped commands. */
	if (!ispipe && !pid_in_pattern && core_uses_pid) {
		err = cn_printf(cn, ".%d", task_tgid_vnr(current));
		if (err)
			return err;
	}
	return ispipe;
}

static int zap_process(struct task_struct *start, int exit_code, int flags)
{
	struct task_struct *t;
	int nr = 0;

	/* ignore all signals except SIGKILL, see prepare_signal() */
	start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
	start->signal->group_exit_code = exit_code;
	start->signal->group_stop_count = 0;

	t = start;
	do {
		task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
		if (t != current && t->mm) {
			sigaddset(&t->pending.signal, SIGKILL);
			signal_wake_up(t, 1);
			nr++;
		}
	} while_each_thread(start, t);

	return nr;
}

static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
			struct core_state *core_state, int exit_code)
{
	struct task_struct *g, *p;
	unsigned long flags;
	int nr = -EAGAIN;

	spin_lock_irq(&tsk->sighand->siglock);
	if (!signal_group_exit(tsk->signal)) {
		mm->core_state = core_state;
		tsk->signal->group_exit_task = tsk;
		nr = zap_process(tsk, exit_code, 0);
		clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
	}
	spin_unlock_irq(&tsk->sighand->siglock);
	if (unlikely(nr < 0))
		return nr;

	tsk->flags |= PF_DUMPCORE;
	if (atomic_read(&mm->mm_users) == nr + 1)
		goto done;
	/*
	 * We should find and kill all tasks which use this mm, and we should
	 * count them correctly into ->nr_threads. We don't take tasklist
	 * lock, but this is safe wrt:
	 *
	 * fork:
	 *	None of sub-threads can fork after zap_process(leader). All
	 *	processes which were created before this point should be
	 *	visible to zap_threads() because copy_process() adds the new
	 *	process to the tail of init_task.tasks list, and lock/unlock
	 *	of ->siglock provides a memory barrier.
	 *
	 * do_exit:
	 *	The caller holds mm->mmap_sem. This means that the task which
	 *	uses this mm can't pass exit_mm(), so it can't exit or clear
	 *	its ->mm.
	 *
	 * de_thread:
	 *	It does list_replace_rcu(&leader->tasks, &current->tasks),
	 *	we must see either old or new leader, this does not matter.
	 *	However, it can change p->sighand, so lock_task_sighand(p)
	 *	must be used. Since p->mm != NULL and we hold ->mmap_sem
	 *	it can't fail.
	 *
	 *	Note also that "g" can be the old leader with ->mm == NULL
	 *	and already unhashed and thus removed from ->thread_group.
	 *	This is OK, __unhash_process()->list_del_rcu() does not
	 *	clear the ->next pointer, we will find the new leader via
	 *	next_thread().
	 */
	rcu_read_lock();
	for_each_process(g) {
		if (g == tsk->group_leader)
			continue;
		if (g->flags & PF_KTHREAD)
			continue;
		p = g;
		do {
			if (p->mm) {
				if (unlikely(p->mm == mm)) {
					lock_task_sighand(p, &flags);
					nr += zap_process(p, exit_code,
							  SIGNAL_GROUP_EXIT);
					unlock_task_sighand(p, &flags);
				}
				break;
			}
		} while_each_thread(g, p);
	}
	rcu_read_unlock();
done:
	atomic_set(&core_state->nr_threads, nr);
	return nr;
}

static int coredump_wait(int exit_code, struct core_state *core_state)
{
	struct task_struct *tsk = current;
	struct mm_struct *mm = tsk->mm;
	int core_waiters = -EBUSY;

	init_completion(&core_state->startup);
	core_state->dumper.task = tsk;
	core_state->dumper.next = NULL;

	down_write(&mm->mmap_sem);
	if (!mm->core_state)
		core_waiters = zap_threads(tsk, mm, core_state, exit_code);
	up_write(&mm->mmap_sem);

	if (core_waiters > 0) {
		struct core_thread *ptr;

		wait_for_completion(&core_state->startup);
		/*
		 * Wait for all the threads to become inactive, so that
		 * all the thread context (extended register state, like
		 * fpu etc) gets copied to the memory.
		 */
		ptr = core_state->dumper.next;
		while (ptr != NULL) {
			wait_task_inactive(ptr->task, 0);
			ptr = ptr->next;
		}
	}

	return core_waiters;
}

static void coredump_finish(struct mm_struct *mm, bool core_dumped)
{
	struct core_thread *curr, *next;
	struct task_struct *task;

	spin_lock_irq(&current->sighand->siglock);
	if (core_dumped && !__fatal_signal_pending(current))
		current->signal->group_exit_code |= 0x80;
	current->signal->group_exit_task = NULL;
	current->signal->flags = SIGNAL_GROUP_EXIT;
	spin_unlock_irq(&current->sighand->siglock);

	next = mm->core_state->dumper.next;
	while ((curr = next) != NULL) {
		next = curr->next;
		task = curr->task;
		/*
		 * see exit_mm(), curr->task must not see
		 * ->task == NULL before we read ->next.
		 */
		smp_mb();
		curr->task = NULL;
		wake_up_process(task);
	}

	mm->core_state = NULL;
}

static bool dump_interrupted(void)
{
	/*
	 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
	 * can do try_to_freeze() and check __fatal_signal_pending(),
	 * but then we need to teach dump_write() to restart and clear
	 * TIF_SIGPENDING.
	 */
	return signal_pending(current);
}

static void wait_for_dump_helpers(struct file *file)
{
	struct pipe_inode_info *pipe = file->private_data;

	pipe_lock(pipe);
	pipe->readers++;
	pipe->writers--;
	wake_up_interruptible_sync(&pipe->wait);
	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
	pipe_unlock(pipe);

	/*
	 * We actually want wait_event_freezable() but then we need
	 * to clear TIF_SIGPENDING and improve dump_interrupted().
	 */
	wait_event_interruptible(pipe->wait, pipe->readers == 1);

	pipe_lock(pipe);
	pipe->readers--;
	pipe->writers++;
	pipe_unlock(pipe);
}

/*
 * umh_pipe_setup
 * helper function to customize the process used
 * to collect the core in userspace.  Specifically
 * it sets up a pipe and installs it as fd 0 (stdin)
 * for the process.  Returns 0 on success, or
 * PTR_ERR on failure.
 * Note that it also sets the core limit to 1.  This
 * is a special value that we use to trap recursive
 * core dumps
 */
static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
{
	struct file *files[2];
	struct coredump_params *cp = (struct coredump_params *)info->data;
	int err = create_pipe_files(files, 0);
	if (err)
		return err;

	cp->file = files[1];

	err = replace_fd(0, files[0], 0);
	fput(files[0]);
	/* and disallow core files too */
	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};

	return err;
}

void do_coredump(const siginfo_t *siginfo)
{
	struct core_state core_state;
	struct core_name cn;
	struct mm_struct *mm = current->mm;
	struct linux_binfmt * binfmt;
	const struct cred *old_cred;
	struct cred *cred;
	int retval = 0;
	int ispipe;
	struct files_struct *displaced;
	/* require nonrelative corefile path and be extra careful */
	bool need_suid_safe = false;
	bool core_dumped = false;
	static atomic_t core_dump_count = ATOMIC_INIT(0);
	struct coredump_params cprm = {
		.siginfo = siginfo,
		.regs = signal_pt_regs(),
		.limit = rlimit(RLIMIT_CORE),
		/*
		 * We must use the same mm->flags while dumping core to avoid
		 * inconsistency of bit flags, since this flag is not protected
		 * by any locks.
		 */
		.mm_flags = mm->flags,
	};

	audit_core_dumps(siginfo->si_signo);

	binfmt = mm->binfmt;
	if (!binfmt || !binfmt->core_dump)
		goto fail;
	if (!__get_dumpable(cprm.mm_flags))
		goto fail;

	cred = prepare_creds();
	if (!cred)
		goto fail;
	/*
	 * We cannot trust fsuid as being the "true" uid of the process
	 * nor do we know its entire history. We only know it was tainted
	 * so we dump it as root in mode 2, and only into a controlled
	 * environment (pipe handler or fully qualified path).
	 */
	if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
		/* Setuid core dump mode */
		cred->fsuid = GLOBAL_ROOT_UID;	/* Dump root private */
		need_suid_safe = true;
	}

	retval = coredump_wait(siginfo->si_signo, &core_state);
	if (retval < 0)
		goto fail_creds;

	old_cred = override_creds(cred);

	ispipe = format_corename(&cn, &cprm);

	if (ispipe) {
		int dump_count;
		char **helper_argv;
		struct subprocess_info *sub_info;

		if (ispipe < 0) {
			printk(KERN_WARNING "format_corename failed\n");
			printk(KERN_WARNING "Aborting core\n");
			goto fail_unlock;
		}

		if (cprm.limit == 1) {
			/* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
			 *
			 * Normally core limits are irrelevant to pipes, since
			 * we're not writing to the file system, but we use
			 * cprm.limit of 1 here as a special value, this is a
			 * consistent way to catch recursive crashes.
			 * We can still crash if the core_pattern binary sets
			 * RLIM_CORE = !1, but it runs as root, and can do
			 * lots of stupid things.
			 *
			 * Note that we use task_tgid_vnr here to grab the pid
			 * of the process group leader.  That way we get the
			 * right pid if a thread in a multi-threaded
			 * core_pattern process dies.
			 */
			printk(KERN_WARNING
				"Process %d(%s) has RLIMIT_CORE set to 1\n",
				task_tgid_vnr(current), current->comm);
			printk(KERN_WARNING "Aborting core\n");
			goto fail_unlock;
		}
		cprm.limit = RLIM_INFINITY;

		dump_count = atomic_inc_return(&core_dump_count);
		if (core_pipe_limit && (core_pipe_limit < dump_count)) {
			printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
			       task_tgid_vnr(current), current->comm);
			printk(KERN_WARNING "Skipping core dump\n");
			goto fail_dropcount;
		}

		helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL);
		if (!helper_argv) {
			printk(KERN_WARNING "%s failed to allocate memory\n",
			       __func__);
			goto fail_dropcount;
		}

		retval = -ENOMEM;
		sub_info = call_usermodehelper_setup(helper_argv[0],
						helper_argv, NULL, GFP_KERNEL,
						umh_pipe_setup, NULL, &cprm);
		if (sub_info)
			retval = call_usermodehelper_exec(sub_info,
							  UMH_WAIT_EXEC);

		argv_free(helper_argv);
		if (retval) {
			printk(KERN_INFO "Core dump to |%s pipe failed\n",
			       cn.corename);
			goto close_fail;
		}
	} else {
		struct inode *inode;

		if (cprm.limit < binfmt->min_coredump)
			goto fail_unlock;

		if (need_suid_safe && cn.corename[0] != '/') {
			printk(KERN_WARNING "Pid %d(%s) can only dump core "\
				"to fully qualified path!\n",
				task_tgid_vnr(current), current->comm);
			printk(KERN_WARNING "Skipping core dump\n");
			goto fail_unlock;
		}

		/*
		 * Unlink the file if it exists unless this is a SUID
		 * binary - in that case, we're running around with root
		 * privs and don't want to unlink another user's coredump.
		 */
		if (!need_suid_safe) {
			mm_segment_t old_fs;

			old_fs = get_fs();
			set_fs(KERNEL_DS);
			/*
			 * If it doesn't exist, that's fine. If there's some
			 * other problem, we'll catch it at the filp_open().
			 */
			(void) sys_unlink((const char __user *)cn.corename);
			set_fs(old_fs);
		}

		/*
		 * There is a race between unlinking and creating the
		 * file, but if that causes an EEXIST here, that's
		 * fine - another process raced with us while creating
		 * the corefile, and the other process won. To userspace,
		 * what matters is that at least one of the two processes
		 * writes its coredump successfully, not which one.
		 */
		cprm.file = filp_open(cn.corename,
				 O_CREAT | 2 | O_NOFOLLOW |
				 O_LARGEFILE | O_EXCL,
				 0600);
		if (IS_ERR(cprm.file))
			goto fail_unlock;

		inode = file_inode(cprm.file);
		if (inode->i_nlink > 1)
			goto close_fail;
		if (d_unhashed(cprm.file->f_path.dentry))
			goto close_fail;
		/*
		 * AK: actually i see no reason to not allow this for named
		 * pipes etc, but keep the previous behaviour for now.
		 */
		if (!S_ISREG(inode->i_mode))
			goto close_fail;
		/*
		 * Don't dump core if the filesystem changed owner or mode
		 * of the file during file creation. This is an issue when
		 * a process dumps core while its cwd is e.g. on a vfat
		 * filesystem.
		 */
		if (!uid_eq(inode->i_uid, current_fsuid()))
			goto close_fail;
		if ((inode->i_mode & 0677) != 0600)
			goto close_fail;
		if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
			goto close_fail;
		if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
			goto close_fail;
	}

	/* get us an unshared descriptor table; almost always a no-op */
	retval = unshare_files(&displaced);
	if (retval)
		goto close_fail;
	if (displaced)
		put_files_struct(displaced);
	if (!dump_interrupted()) {
		file_start_write(cprm.file);
		core_dumped = binfmt->core_dump(&cprm);
		file_end_write(cprm.file);
	}
	if (ispipe && core_pipe_limit)
		wait_for_dump_helpers(cprm.file);
close_fail:
	if (cprm.file)
		filp_close(cprm.file, NULL);
fail_dropcount:
	if (ispipe)
		atomic_dec(&core_dump_count);
fail_unlock:
	kfree(cn.corename);
	coredump_finish(mm, core_dumped);
	revert_creds(old_cred);
fail_creds:
	put_cred(cred);
fail:
	return;
}

/*
 * Core dumping helper functions.  These are the only things you should
 * do on a core-file: use only these functions to write out all the
 * necessary info.
 */
int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
{
	struct file *file = cprm->file;
	loff_t pos = file->f_pos;
	ssize_t n;
	if (cprm->written + nr > cprm->limit)
		return 0;
	while (nr) {
		if (dump_interrupted())
			return 0;
		n = __kernel_write(file, addr, nr, &pos);
		if (n <= 0)
			return 0;
		file->f_pos = pos;
		cprm->written += n;
		nr -= n;
	}
	return 1;
}
EXPORT_SYMBOL(dump_emit);

int dump_skip(struct coredump_params *cprm, size_t nr)
{
	static char zeroes[PAGE_SIZE];
	struct file *file = cprm->file;
	if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
		if (cprm->written + nr > cprm->limit)
			return 0;
		if (dump_interrupted() ||
		    file->f_op->llseek(file, nr, SEEK_CUR) < 0)
			return 0;
		cprm->written += nr;
		return 1;
	} else {
		while (nr > PAGE_SIZE) {
			if (!dump_emit(cprm, zeroes, PAGE_SIZE))
				return 0;
			nr -= PAGE_SIZE;
		}
		return dump_emit(cprm, zeroes, nr);
	}
}
EXPORT_SYMBOL(dump_skip);

int dump_align(struct coredump_params *cprm, int align)
{
	unsigned mod = cprm->written & (align - 1);
	if (align & (align - 1))
		return 0;
	return mod ? dump_skip(cprm, align - mod) : 1;
}
EXPORT_SYMBOL(dump_align);