summaryrefslogtreecommitdiff
path: root/kernel/cred.c
blob: c73a87a4df13fa02d96661fa889ec9fa5f4fd7ea (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
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
// SPDX-License-Identifier: GPL-2.0-or-later
/* Task credentials management - see Documentation/security/credentials.rst
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */
#include <linux/export.h>
#include <linux/cred.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/sched/coredump.h>
#include <linux/key.h>
#include <linux/keyctl.h>
#include <linux/init_task.h>
#include <linux/security.h>
#include <linux/binfmts.h>
#include <linux/cn_proc.h>
#include <linux/uidgid.h>

#if 0
#define kdebug(FMT, ...)						\
	printk("[%-5.5s%5u] " FMT "\n",					\
	       current->comm, current->pid, ##__VA_ARGS__)
#else
#define kdebug(FMT, ...)						\
do {									\
	if (0)								\
		no_printk("[%-5.5s%5u] " FMT "\n",			\
			  current->comm, current->pid, ##__VA_ARGS__);	\
} while (0)
#endif

static struct kmem_cache *cred_jar;

/* init to 2 - one for init_task, one to ensure it is never freed */
struct group_info init_groups = { .usage = ATOMIC_INIT(2) };

/*
 * The initial credentials for the initial task
 */
struct cred init_cred = {
	.usage			= ATOMIC_INIT(4),
#ifdef CONFIG_DEBUG_CREDENTIALS
	.subscribers		= ATOMIC_INIT(2),
	.magic			= CRED_MAGIC,
#endif
	.uid			= GLOBAL_ROOT_UID,
	.gid			= GLOBAL_ROOT_GID,
	.suid			= GLOBAL_ROOT_UID,
	.sgid			= GLOBAL_ROOT_GID,
	.euid			= GLOBAL_ROOT_UID,
	.egid			= GLOBAL_ROOT_GID,
	.fsuid			= GLOBAL_ROOT_UID,
	.fsgid			= GLOBAL_ROOT_GID,
	.securebits		= SECUREBITS_DEFAULT,
	.cap_inheritable	= CAP_EMPTY_SET,
	.cap_permitted		= CAP_FULL_SET,
	.cap_effective		= CAP_FULL_SET,
	.cap_bset		= CAP_FULL_SET,
	.user			= INIT_USER,
	.user_ns		= &init_user_ns,
	.group_info		= &init_groups,
};

static inline void set_cred_subscribers(struct cred *cred, int n)
{
#ifdef CONFIG_DEBUG_CREDENTIALS
	atomic_set(&cred->subscribers, n);
#endif
}

static inline int read_cred_subscribers(const struct cred *cred)
{
#ifdef CONFIG_DEBUG_CREDENTIALS
	return atomic_read(&cred->subscribers);
#else
	return 0;
#endif
}

static inline void alter_cred_subscribers(const struct cred *_cred, int n)
{
#ifdef CONFIG_DEBUG_CREDENTIALS
	struct cred *cred = (struct cred *) _cred;

	atomic_add(n, &cred->subscribers);
#endif
}

/*
 * The RCU callback to actually dispose of a set of credentials
 */
static void put_cred_rcu(struct rcu_head *rcu)
{
	struct cred *cred = container_of(rcu, struct cred, rcu);

	kdebug("put_cred_rcu(%p)", cred);

#ifdef CONFIG_DEBUG_CREDENTIALS
	if (cred->magic != CRED_MAGIC_DEAD ||
	    atomic_read(&cred->usage) != 0 ||
	    read_cred_subscribers(cred) != 0)
		panic("CRED: put_cred_rcu() sees %p with"
		      " mag %x, put %p, usage %d, subscr %d\n",
		      cred, cred->magic, cred->put_addr,
		      atomic_read(&cred->usage),
		      read_cred_subscribers(cred));
#else
	if (atomic_read(&cred->usage) != 0)
		panic("CRED: put_cred_rcu() sees %p with usage %d\n",
		      cred, atomic_read(&cred->usage));
#endif

	security_cred_free(cred);
	key_put(cred->session_keyring);
	key_put(cred->process_keyring);
	key_put(cred->thread_keyring);
	key_put(cred->request_key_auth);
	if (cred->group_info)
		put_group_info(cred->group_info);
	free_uid(cred->user);
	put_user_ns(cred->user_ns);
	kmem_cache_free(cred_jar, cred);
}

/**
 * __put_cred - Destroy a set of credentials
 * @cred: The record to release
 *
 * Destroy a set of credentials on which no references remain.
 */
void __put_cred(struct cred *cred)
{
	kdebug("__put_cred(%p{%d,%d})", cred,
	       atomic_read(&cred->usage),
	       read_cred_subscribers(cred));

	BUG_ON(atomic_read(&cred->usage) != 0);
#ifdef CONFIG_DEBUG_CREDENTIALS
	BUG_ON(read_cred_subscribers(cred) != 0);
	cred->magic = CRED_MAGIC_DEAD;
	cred->put_addr = __builtin_return_address(0);
#endif
	BUG_ON(cred == current->cred);
	BUG_ON(cred == current->real_cred);

	call_rcu(&cred->rcu, put_cred_rcu);
}
EXPORT_SYMBOL(__put_cred);

/*
 * Clean up a task's credentials when it exits
 */
void exit_creds(struct task_struct *tsk)
{
	struct cred *cred;

	kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
	       atomic_read(&tsk->cred->usage),
	       read_cred_subscribers(tsk->cred));

	cred = (struct cred *) tsk->real_cred;
	tsk->real_cred = NULL;
	validate_creds(cred);
	alter_cred_subscribers(cred, -1);
	put_cred(cred);

	cred = (struct cred *) tsk->cred;
	tsk->cred = NULL;
	validate_creds(cred);
	alter_cred_subscribers(cred, -1);
	put_cred(cred);
}

/**
 * get_task_cred - Get another task's objective credentials
 * @task: The task to query
 *
 * Get the objective credentials of a task, pinning them so that they can't go
 * away.  Accessing a task's credentials directly is not permitted.
 *
 * The caller must also make sure task doesn't get deleted, either by holding a
 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
 */
const struct cred *get_task_cred(struct task_struct *task)
{
	const struct cred *cred;

	rcu_read_lock();

	do {
		cred = __task_cred((task));
		BUG_ON(!cred);
	} while (!get_cred_rcu(cred));

	rcu_read_unlock();
	return cred;
}
EXPORT_SYMBOL(get_task_cred);

/*
 * Allocate blank credentials, such that the credentials can be filled in at a
 * later date without risk of ENOMEM.
 */
struct cred *cred_alloc_blank(void)
{
	struct cred *new;

	new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
	if (!new)
		return NULL;

	atomic_set(&new->usage, 1);
#ifdef CONFIG_DEBUG_CREDENTIALS
	new->magic = CRED_MAGIC;
#endif

	if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
		goto error;

	return new;

error:
	abort_creds(new);
	return NULL;
}

/**
 * prepare_creds - Prepare a new set of credentials for modification
 *
 * Prepare a new set of task credentials for modification.  A task's creds
 * shouldn't generally be modified directly, therefore this function is used to
 * prepare a new copy, which the caller then modifies and then commits by
 * calling commit_creds().
 *
 * Preparation involves making a copy of the objective creds for modification.
 *
 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
 *
 * Call commit_creds() or abort_creds() to clean up.
 */
struct cred *prepare_creds(void)
{
	struct task_struct *task = current;
	const struct cred *old;
	struct cred *new;

	validate_process_creds();

	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
	if (!new)
		return NULL;

	kdebug("prepare_creds() alloc %p", new);

	old = task->cred;
	memcpy(new, old, sizeof(struct cred));

	atomic_set(&new->usage, 1);
	set_cred_subscribers(new, 0);
	get_group_info(new->group_info);
	get_uid(new->user);
	get_user_ns(new->user_ns);

#ifdef CONFIG_KEYS
	key_get(new->session_keyring);
	key_get(new->process_keyring);
	key_get(new->thread_keyring);
	key_get(new->request_key_auth);
#endif

#ifdef CONFIG_SECURITY
	new->security = NULL;
#endif

	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
		goto error;
	validate_creds(new);
	return new;

error:
	abort_creds(new);
	return NULL;
}
EXPORT_SYMBOL(prepare_creds);

/*
 * Prepare credentials for current to perform an execve()
 * - The caller must hold ->cred_guard_mutex
 */
struct cred *prepare_exec_creds(void)
{
	struct cred *new;

	new = prepare_creds();
	if (!new)
		return new;

#ifdef CONFIG_KEYS
	/* newly exec'd tasks don't get a thread keyring */
	key_put(new->thread_keyring);
	new->thread_keyring = NULL;

	/* inherit the session keyring; new process keyring */
	key_put(new->process_keyring);
	new->process_keyring = NULL;
#endif

	return new;
}

/*
 * Copy credentials for the new process created by fork()
 *
 * We share if we can, but under some circumstances we have to generate a new
 * set.
 *
 * The new process gets the current process's subjective credentials as its
 * objective and subjective credentials
 */
int copy_creds(struct task_struct *p, unsigned long clone_flags)
{
	struct cred *new;
	int ret;

	if (
#ifdef CONFIG_KEYS
		!p->cred->thread_keyring &&
#endif
		clone_flags & CLONE_THREAD
	    ) {
		p->real_cred = get_cred(p->cred);
		get_cred(p->cred);
		alter_cred_subscribers(p->cred, 2);
		kdebug("share_creds(%p{%d,%d})",
		       p->cred, atomic_read(&p->cred->usage),
		       read_cred_subscribers(p->cred));
		atomic_inc(&p->cred->user->processes);
		return 0;
	}

	new = prepare_creds();
	if (!new)
		return -ENOMEM;

	if (clone_flags & CLONE_NEWUSER) {
		ret = create_user_ns(new);
		if (ret < 0)
			goto error_put;
	}

#ifdef CONFIG_KEYS
	/* new threads get their own thread keyrings if their parent already
	 * had one */
	if (new->thread_keyring) {
		key_put(new->thread_keyring);
		new->thread_keyring = NULL;
		if (clone_flags & CLONE_THREAD)
			install_thread_keyring_to_cred(new);
	}

	/* The process keyring is only shared between the threads in a process;
	 * anything outside of those threads doesn't inherit.
	 */
	if (!(clone_flags & CLONE_THREAD)) {
		key_put(new->process_keyring);
		new->process_keyring = NULL;
	}
#endif

	atomic_inc(&new->user->processes);
	p->cred = p->real_cred = get_cred(new);
	alter_cred_subscribers(new, 2);
	validate_creds(new);
	return 0;

error_put:
	put_cred(new);
	return ret;
}

static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
{
	const struct user_namespace *set_ns = set->user_ns;
	const struct user_namespace *subset_ns = subset->user_ns;

	/* If the two credentials are in the same user namespace see if
	 * the capabilities of subset are a subset of set.
	 */
	if (set_ns == subset_ns)
		return cap_issubset(subset->cap_permitted, set->cap_permitted);

	/* The credentials are in a different user namespaces
	 * therefore one is a subset of the other only if a set is an
	 * ancestor of subset and set->euid is owner of subset or one
	 * of subsets ancestors.
	 */
	for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
		if ((set_ns == subset_ns->parent)  &&
		    uid_eq(subset_ns->owner, set->euid))
			return true;
	}

	return false;
}

/**
 * commit_creds - Install new credentials upon the current task
 * @new: The credentials to be assigned
 *
 * Install a new set of credentials to the current task, using RCU to replace
 * the old set.  Both the objective and the subjective credentials pointers are
 * updated.  This function may not be called if the subjective credentials are
 * in an overridden state.
 *
 * This function eats the caller's reference to the new credentials.
 *
 * Always returns 0 thus allowing this function to be tail-called at the end
 * of, say, sys_setgid().
 */
int commit_creds(struct cred *new)
{
	struct task_struct *task = current;
	const struct cred *old = task->real_cred;

	kdebug("commit_creds(%p{%d,%d})", new,
	       atomic_read(&new->usage),
	       read_cred_subscribers(new));

	BUG_ON(task->cred != old);
#ifdef CONFIG_DEBUG_CREDENTIALS
	BUG_ON(read_cred_subscribers(old) < 2);
	validate_creds(old);
	validate_creds(new);
#endif
	BUG_ON(atomic_read(&new->usage) < 1);

	get_cred(new); /* we will require a ref for the subj creds too */

	/* dumpability changes */
	if (!uid_eq(old->euid, new->euid) ||
	    !gid_eq(old->egid, new->egid) ||
	    !uid_eq(old->fsuid, new->fsuid) ||
	    !gid_eq(old->fsgid, new->fsgid) ||
	    !cred_cap_issubset(old, new)) {
		if (task->mm)
			set_dumpable(task->mm, suid_dumpable);
		task->pdeath_signal = 0;
		/*
		 * If a task drops privileges and becomes nondumpable,
		 * the dumpability change must become visible before
		 * the credential change; otherwise, a __ptrace_may_access()
		 * racing with this change may be able to attach to a task it
		 * shouldn't be able to attach to (as if the task had dropped
		 * privileges without becoming nondumpable).
		 * Pairs with a read barrier in __ptrace_may_access().
		 */
		smp_wmb();
	}

	/* alter the thread keyring */
	if (!uid_eq(new->fsuid, old->fsuid))
		key_fsuid_changed(task);
	if (!gid_eq(new->fsgid, old->fsgid))
		key_fsgid_changed(task);

	/* do it
	 * RLIMIT_NPROC limits on user->processes have already been checked
	 * in set_user().
	 */
	alter_cred_subscribers(new, 2);
	if (new->user != old->user)
		atomic_inc(&new->user->processes);
	rcu_assign_pointer(task->real_cred, new);
	rcu_assign_pointer(task->cred, new);
	if (new->user != old->user)
		atomic_dec(&old->user->processes);
	alter_cred_subscribers(old, -2);

	/* send notifications */
	if (!uid_eq(new->uid,   old->uid)  ||
	    !uid_eq(new->euid,  old->euid) ||
	    !uid_eq(new->suid,  old->suid) ||
	    !uid_eq(new->fsuid, old->fsuid))
		proc_id_connector(task, PROC_EVENT_UID);

	if (!gid_eq(new->gid,   old->gid)  ||
	    !gid_eq(new->egid,  old->egid) ||
	    !gid_eq(new->sgid,  old->sgid) ||
	    !gid_eq(new->fsgid, old->fsgid))
		proc_id_connector(task, PROC_EVENT_GID);

	/* release the old obj and subj refs both */
	put_cred(old);
	put_cred(old);
	return 0;
}
EXPORT_SYMBOL(commit_creds);

/**
 * abort_creds - Discard a set of credentials and unlock the current task
 * @new: The credentials that were going to be applied
 *
 * Discard a set of credentials that were under construction and unlock the
 * current task.
 */
void abort_creds(struct cred *new)
{
	kdebug("abort_creds(%p{%d,%d})", new,
	       atomic_read(&new->usage),
	       read_cred_subscribers(new));

#ifdef CONFIG_DEBUG_CREDENTIALS
	BUG_ON(read_cred_subscribers(new) != 0);
#endif
	BUG_ON(atomic_read(&new->usage) < 1);
	put_cred(new);
}
EXPORT_SYMBOL(abort_creds);

/**
 * override_creds - Override the current process's subjective credentials
 * @new: The credentials to be assigned
 *
 * Install a set of temporary override subjective credentials on the current
 * process, returning the old set for later reversion.
 */
const struct cred *override_creds(const struct cred *new)
{
	const struct cred *old = current->cred;

	kdebug("override_creds(%p{%d,%d})", new,
	       atomic_read(&new->usage),
	       read_cred_subscribers(new));

	validate_creds(old);
	validate_creds(new);
	get_cred(new);
	alter_cred_subscribers(new, 1);
	rcu_assign_pointer(current->cred, new);
	alter_cred_subscribers(old, -1);

	kdebug("override_creds() = %p{%d,%d}", old,
	       atomic_read(&old->usage),
	       read_cred_subscribers(old));
	return old;
}
EXPORT_SYMBOL(override_creds);

/**
 * revert_creds - Revert a temporary subjective credentials override
 * @old: The credentials to be restored
 *
 * Revert a temporary set of override subjective credentials to an old set,
 * discarding the override set.
 */
void revert_creds(const struct cred *old)
{
	const struct cred *override = current->cred;

	kdebug("revert_creds(%p{%d,%d})", old,
	       atomic_read(&old->usage),
	       read_cred_subscribers(old));

	validate_creds(old);
	validate_creds(override);
	alter_cred_subscribers(old, 1);
	rcu_assign_pointer(current->cred, old);
	alter_cred_subscribers(override, -1);
	put_cred(override);
}
EXPORT_SYMBOL(revert_creds);

/**
 * cred_fscmp - Compare two credentials with respect to filesystem access.
 * @a: The first credential
 * @b: The second credential
 *
 * cred_cmp() will return zero if both credentials have the same
 * fsuid, fsgid, and supplementary groups.  That is, if they will both
 * provide the same access to files based on mode/uid/gid.
 * If the credentials are different, then either -1 or 1 will
 * be returned depending on whether @a comes before or after @b
 * respectively in an arbitrary, but stable, ordering of credentials.
 *
 * Return: -1, 0, or 1 depending on comparison
 */
int cred_fscmp(const struct cred *a, const struct cred *b)
{
	struct group_info *ga, *gb;
	int g;

	if (a == b)
		return 0;
	if (uid_lt(a->fsuid, b->fsuid))
		return -1;
	if (uid_gt(a->fsuid, b->fsuid))
		return 1;

	if (gid_lt(a->fsgid, b->fsgid))
		return -1;
	if (gid_gt(a->fsgid, b->fsgid))
		return 1;

	ga = a->group_info;
	gb = b->group_info;
	if (ga == gb)
		return 0;
	if (ga == NULL)
		return -1;
	if (gb == NULL)
		return 1;
	if (ga->ngroups < gb->ngroups)
		return -1;
	if (ga->ngroups > gb->ngroups)
		return 1;

	for (g = 0; g < ga->ngroups; g++) {
		if (gid_lt(ga->gid[g], gb->gid[g]))
			return -1;
		if (gid_gt(ga->gid[g], gb->gid[g]))
			return 1;
	}
	return 0;
}
EXPORT_SYMBOL(cred_fscmp);

/*
 * initialise the credentials stuff
 */
void __init cred_init(void)
{
	/* allocate a slab in which we can store credentials */
	cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
}

/**
 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
 * @daemon: A userspace daemon to be used as a reference
 *
 * Prepare a set of credentials for a kernel service.  This can then be used to
 * override a task's own credentials so that work can be done on behalf of that
 * task that requires a different subjective context.
 *
 * @daemon is used to provide a base for the security record, but can be NULL.
 * If @daemon is supplied, then the security data will be derived from that;
 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
 *
 * The caller may change these controls afterwards if desired.
 *
 * Returns the new credentials or NULL if out of memory.
 *
 * Does not take, and does not return holding current->cred_replace_mutex.
 */
struct cred *prepare_kernel_cred(struct task_struct *daemon)
{
	const struct cred *old;
	struct cred *new;

	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
	if (!new)
		return NULL;

	kdebug("prepare_kernel_cred() alloc %p", new);

	if (daemon)
		old = get_task_cred(daemon);
	else
		old = get_cred(&init_cred);

	validate_creds(old);

	*new = *old;
	atomic_set(&new->usage, 1);
	set_cred_subscribers(new, 0);
	get_uid(new->user);
	get_user_ns(new->user_ns);
	get_group_info(new->group_info);

#ifdef CONFIG_KEYS
	new->session_keyring = NULL;
	new->process_keyring = NULL;
	new->thread_keyring = NULL;
	new->request_key_auth = NULL;
	new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
#endif

#ifdef CONFIG_SECURITY
	new->security = NULL;
#endif
	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
		goto error;

	put_cred(old);
	validate_creds(new);
	return new;

error:
	put_cred(new);
	put_cred(old);
	return NULL;
}
EXPORT_SYMBOL(prepare_kernel_cred);

/**
 * set_security_override - Set the security ID in a set of credentials
 * @new: The credentials to alter
 * @secid: The LSM security ID to set
 *
 * Set the LSM security ID in a set of credentials so that the subjective
 * security is overridden when an alternative set of credentials is used.
 */
int set_security_override(struct cred *new, u32 secid)
{
	return security_kernel_act_as(new, secid);
}
EXPORT_SYMBOL(set_security_override);

/**
 * set_security_override_from_ctx - Set the security ID in a set of credentials
 * @new: The credentials to alter
 * @secctx: The LSM security context to generate the security ID from.
 *
 * Set the LSM security ID in a set of credentials so that the subjective
 * security is overridden when an alternative set of credentials is used.  The
 * security ID is specified in string form as a security context to be
 * interpreted by the LSM.
 */
int set_security_override_from_ctx(struct cred *new, const char *secctx)
{
	u32 secid;
	int ret;

	ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
	if (ret < 0)
		return ret;

	return set_security_override(new, secid);
}
EXPORT_SYMBOL(set_security_override_from_ctx);

/**
 * set_create_files_as - Set the LSM file create context in a set of credentials
 * @new: The credentials to alter
 * @inode: The inode to take the context from
 *
 * Change the LSM file creation context in a set of credentials to be the same
 * as the object context of the specified inode, so that the new inodes have
 * the same MAC context as that inode.
 */
int set_create_files_as(struct cred *new, struct inode *inode)
{
	if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
		return -EINVAL;
	new->fsuid = inode->i_uid;
	new->fsgid = inode->i_gid;
	return security_kernel_create_files_as(new, inode);
}
EXPORT_SYMBOL(set_create_files_as);

#ifdef CONFIG_DEBUG_CREDENTIALS

bool creds_are_invalid(const struct cred *cred)
{
	if (cred->magic != CRED_MAGIC)
		return true;
	return false;
}
EXPORT_SYMBOL(creds_are_invalid);

/*
 * dump invalid credentials
 */
static void dump_invalid_creds(const struct cred *cred, const char *label,
			       const struct task_struct *tsk)
{
	printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
	       label, cred,
	       cred == &init_cred ? "[init]" : "",
	       cred == tsk->real_cred ? "[real]" : "",
	       cred == tsk->cred ? "[eff]" : "");
	printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
	       cred->magic, cred->put_addr);
	printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
	       atomic_read(&cred->usage),
	       read_cred_subscribers(cred));
	printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
		from_kuid_munged(&init_user_ns, cred->uid),
		from_kuid_munged(&init_user_ns, cred->euid),
		from_kuid_munged(&init_user_ns, cred->suid),
		from_kuid_munged(&init_user_ns, cred->fsuid));
	printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
		from_kgid_munged(&init_user_ns, cred->gid),
		from_kgid_munged(&init_user_ns, cred->egid),
		from_kgid_munged(&init_user_ns, cred->sgid),
		from_kgid_munged(&init_user_ns, cred->fsgid));
#ifdef CONFIG_SECURITY
	printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
	if ((unsigned long) cred->security >= PAGE_SIZE &&
	    (((unsigned long) cred->security & 0xffffff00) !=
	     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
		printk(KERN_ERR "CRED: ->security {%x, %x}\n",
		       ((u32*)cred->security)[0],
		       ((u32*)cred->security)[1]);
#endif
}

/*
 * report use of invalid credentials
 */
void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
{
	printk(KERN_ERR "CRED: Invalid credentials\n");
	printk(KERN_ERR "CRED: At %s:%u\n", file, line);
	dump_invalid_creds(cred, "Specified", current);
	BUG();
}
EXPORT_SYMBOL(__invalid_creds);

/*
 * check the credentials on a process
 */
void __validate_process_creds(struct task_struct *tsk,
			      const char *file, unsigned line)
{
	if (tsk->cred == tsk->real_cred) {
		if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
			     creds_are_invalid(tsk->cred)))
			goto invalid_creds;
	} else {
		if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
			     read_cred_subscribers(tsk->cred) < 1 ||
			     creds_are_invalid(tsk->real_cred) ||
			     creds_are_invalid(tsk->cred)))
			goto invalid_creds;
	}
	return;

invalid_creds:
	printk(KERN_ERR "CRED: Invalid process credentials\n");
	printk(KERN_ERR "CRED: At %s:%u\n", file, line);

	dump_invalid_creds(tsk->real_cred, "Real", tsk);
	if (tsk->cred != tsk->real_cred)
		dump_invalid_creds(tsk->cred, "Effective", tsk);
	else
		printk(KERN_ERR "CRED: Effective creds == Real creds\n");
	BUG();
}
EXPORT_SYMBOL(__validate_process_creds);

/*
 * check creds for do_exit()
 */
void validate_creds_for_do_exit(struct task_struct *tsk)
{
	kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
	       tsk->real_cred, tsk->cred,
	       atomic_read(&tsk->cred->usage),
	       read_cred_subscribers(tsk->cred));

	__validate_process_creds(tsk, __FILE__, __LINE__);
}

#endif /* CONFIG_DEBUG_CREDENTIALS */