cred.c 22.5 KB
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879
/* Task credentials management - see Documentation/security/credentials.txt
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */
#include <linux/export.h>
#include <linux/cred.h>
#include <linux/slab.h>
#include <linux/sched.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>

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

static struct kmem_cache *cred_jar;

/*
 * The common credentials for the initial task's thread group
 */
#ifdef CONFIG_KEYS
static struct thread_group_cred init_tgcred = {
	.usage	= ATOMIC_INIT(2),
	.tgid	= 0,
	.lock	= __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock),
};
#endif

/*
 * 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,
#ifdef CONFIG_KEYS
	.tgcred			= &init_tgcred,
#endif
};

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
}

/*
 * Dispose of the shared task group credentials
 */
#ifdef CONFIG_KEYS
static void release_tgcred_rcu(struct rcu_head *rcu)
{
	struct thread_group_cred *tgcred =
		container_of(rcu, struct thread_group_cred, rcu);

	BUG_ON(atomic_read(&tgcred->usage) != 0);

	key_put(tgcred->session_keyring);
	key_put(tgcred->process_keyring);
	kfree(tgcred);
}
#endif

/*
 * Release a set of thread group credentials.
 */
static void release_tgcred(struct cred *cred)
{
#ifdef CONFIG_KEYS
	struct thread_group_cred *tgcred = cred->tgcred;

	if (atomic_dec_and_test(&tgcred->usage))
		call_rcu(&tgcred->rcu, release_tgcred_rcu);
#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->thread_keyring);
	key_put(cred->request_key_auth);
	release_tgcred(cred);
	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 (!atomic_inc_not_zero(&((struct cred *)cred)->usage));

	rcu_read_unlock();
	return 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;

#ifdef CONFIG_KEYS
	new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
	if (!new->tgcred) {
		kmem_cache_free(cred_jar, new);
		return NULL;
	}
	atomic_set(&new->tgcred->usage, 1);
#endif

	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->thread_keyring);
	key_get(new->request_key_auth);
	atomic_inc(&new->tgcred->usage);
#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 thread_group_cred *tgcred = NULL;
	struct cred *new;

#ifdef CONFIG_KEYS
	tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
	if (!tgcred)
		return NULL;
#endif

	new = prepare_creds();
	if (!new) {
		kfree(tgcred);
		return new;
	}

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

	/* create a new per-thread-group creds for all this set of threads to
	 * share */
	memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));

	atomic_set(&tgcred->usage, 1);
	spin_lock_init(&tgcred->lock);

	/* inherit the session keyring; new process keyring */
	key_get(tgcred->session_keyring);
	tgcred->process_keyring = NULL;

	release_tgcred(new);
	new->tgcred = tgcred;
#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)
{
#ifdef CONFIG_KEYS
	struct thread_group_cred *tgcred;
#endif
	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);
	}

	/* we share the process and session keyrings between all the threads in
	 * a process - this is slightly icky as we violate COW credentials a
	 * bit */
	if (!(clone_flags & CLONE_THREAD)) {
		tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
		if (!tgcred) {
			ret = -ENOMEM;
			goto error_put;
		}
		atomic_set(&tgcred->usage, 1);
		spin_lock_init(&tgcred->lock);
		tgcred->process_keyring = NULL;
		tgcred->session_keyring = key_get(new->tgcred->session_keyring);

		release_tgcred(new);
		new->tgcred = tgcred;
	}
#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;
}

/**
 * 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) ||
	    !cap_issubset(new->cap_permitted, old->cap_permitted)) {
		if (task->mm)
			set_dumpable(task->mm, suid_dumpable);
		task->pdeath_signal = 0;
		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);

/*
 * 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, 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)
{
#ifdef CONFIG_KEYS
	struct thread_group_cred *tgcred;
#endif
	const struct cred *old;
	struct cred *new;

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

#ifdef CONFIG_KEYS
	tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
	if (!tgcred) {
		kmem_cache_free(cred_jar, new);
		return NULL;
	}
#endif

	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
	atomic_set(&tgcred->usage, 1);
	spin_lock_init(&tgcred->lock);
	tgcred->process_keyring = NULL;
	tgcred->session_keyring = NULL;
	new->tgcred = tgcred;
	new->request_key_auth = NULL;
	new->thread_keyring = 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)
{
	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;
#ifdef CONFIG_SECURITY_SELINUX
	/*
	 * cred->security == NULL if security_cred_alloc_blank() or
	 * security_prepare_creds() returned an error.
	 */
	if (selinux_is_enabled() && cred->security) {
		if ((unsigned long) cred->security < PAGE_SIZE)
			return true;
		if ((*(u32 *)cred->security & 0xffffff00) ==
		    (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
			return true;
	}
#endif
	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 */