1/* Task credentials management - see Documentation/security/credentials.txt
 
  2 *
  3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
  4 * Written by David Howells (dhowells@redhat.com)
  5 *
  6 * This program is free software; you can redistribute it and/or
  7 * modify it under the terms of the GNU General Public Licence
  8 * as published by the Free Software Foundation; either version
  9 * 2 of the Licence, or (at your option) any later version.
 10 */
 
 
 
 11#include <linux/export.h>
 12#include <linux/cred.h>
 13#include <linux/slab.h>
 14#include <linux/sched.h>
 
 15#include <linux/key.h>
 16#include <linux/keyctl.h>
 17#include <linux/init_task.h>
 18#include <linux/security.h>
 19#include <linux/binfmts.h>
 20#include <linux/cn_proc.h>
 
 21
 22#if 0
 23#define kdebug(FMT, ...) \
 24	printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
 
 25#else
 26#define kdebug(FMT, ...) \
 27	no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
 
 
 
 
 28#endif
 29
 30static struct kmem_cache *cred_jar;
 31
 32/*
 33 * The common credentials for the initial task's thread group
 34 */
 35#ifdef CONFIG_KEYS
 36static struct thread_group_cred init_tgcred = {
 37	.usage	= ATOMIC_INIT(2),
 38	.tgid	= 0,
 39	.lock	= __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock),
 40};
 41#endif
 42
 43/*
 44 * The initial credentials for the initial task
 45 */
 46struct cred init_cred = {
 47	.usage			= ATOMIC_INIT(4),
 48#ifdef CONFIG_DEBUG_CREDENTIALS
 49	.subscribers		= ATOMIC_INIT(2),
 50	.magic			= CRED_MAGIC,
 51#endif
 52	.uid			= GLOBAL_ROOT_UID,
 53	.gid			= GLOBAL_ROOT_GID,
 54	.suid			= GLOBAL_ROOT_UID,
 55	.sgid			= GLOBAL_ROOT_GID,
 56	.euid			= GLOBAL_ROOT_UID,
 57	.egid			= GLOBAL_ROOT_GID,
 58	.fsuid			= GLOBAL_ROOT_UID,
 59	.fsgid			= GLOBAL_ROOT_GID,
 60	.securebits		= SECUREBITS_DEFAULT,
 61	.cap_inheritable	= CAP_EMPTY_SET,
 62	.cap_permitted		= CAP_FULL_SET,
 63	.cap_effective		= CAP_FULL_SET,
 64	.cap_bset		= CAP_FULL_SET,
 65	.user			= INIT_USER,
 66	.user_ns		= &init_user_ns,
 67	.group_info		= &init_groups,
 68#ifdef CONFIG_KEYS
 69	.tgcred			= &init_tgcred,
 70#endif
 71};
 72
 73static inline void set_cred_subscribers(struct cred *cred, int n)
 74{
 75#ifdef CONFIG_DEBUG_CREDENTIALS
 76	atomic_set(&cred->subscribers, n);
 77#endif
 78}
 79
 80static inline int read_cred_subscribers(const struct cred *cred)
 81{
 82#ifdef CONFIG_DEBUG_CREDENTIALS
 83	return atomic_read(&cred->subscribers);
 84#else
 85	return 0;
 86#endif
 87}
 88
 89static inline void alter_cred_subscribers(const struct cred *_cred, int n)
 90{
 91#ifdef CONFIG_DEBUG_CREDENTIALS
 92	struct cred *cred = (struct cred *) _cred;
 93
 94	atomic_add(n, &cred->subscribers);
 95#endif
 96}
 97
 98/*
 99 * Dispose of the shared task group credentials
100 */
101#ifdef CONFIG_KEYS
102static void release_tgcred_rcu(struct rcu_head *rcu)
103{
104	struct thread_group_cred *tgcred =
105		container_of(rcu, struct thread_group_cred, rcu);
106
107	BUG_ON(atomic_read(&tgcred->usage) != 0);
108
109	key_put(tgcred->session_keyring);
110	key_put(tgcred->process_keyring);
111	kfree(tgcred);
112}
113#endif
114
115/*
116 * Release a set of thread group credentials.
117 */
118static void release_tgcred(struct cred *cred)
119{
120#ifdef CONFIG_KEYS
121	struct thread_group_cred *tgcred = cred->tgcred;
122
123	if (atomic_dec_and_test(&tgcred->usage))
124		call_rcu(&tgcred->rcu, release_tgcred_rcu);
125#endif
126}
127
128/*
129 * The RCU callback to actually dispose of a set of credentials
130 */
131static void put_cred_rcu(struct rcu_head *rcu)
132{
133	struct cred *cred = container_of(rcu, struct cred, rcu);
134
135	kdebug("put_cred_rcu(%p)", cred);
136
137#ifdef CONFIG_DEBUG_CREDENTIALS
138	if (cred->magic != CRED_MAGIC_DEAD ||
139	    atomic_read(&cred->usage) != 0 ||
140	    read_cred_subscribers(cred) != 0)
141		panic("CRED: put_cred_rcu() sees %p with"
142		      " mag %x, put %p, usage %d, subscr %d\n",
143		      cred, cred->magic, cred->put_addr,
144		      atomic_read(&cred->usage),
145		      read_cred_subscribers(cred));
146#else
147	if (atomic_read(&cred->usage) != 0)
148		panic("CRED: put_cred_rcu() sees %p with usage %d\n",
149		      cred, atomic_read(&cred->usage));
150#endif
151
152	security_cred_free(cred);
 
 
153	key_put(cred->thread_keyring);
154	key_put(cred->request_key_auth);
155	release_tgcred(cred);
156	if (cred->group_info)
157		put_group_info(cred->group_info);
158	free_uid(cred->user);
 
 
159	put_user_ns(cred->user_ns);
160	kmem_cache_free(cred_jar, cred);
161}
162
163/**
164 * __put_cred - Destroy a set of credentials
165 * @cred: The record to release
166 *
167 * Destroy a set of credentials on which no references remain.
168 */
169void __put_cred(struct cred *cred)
170{
171	kdebug("__put_cred(%p{%d,%d})", cred,
172	       atomic_read(&cred->usage),
173	       read_cred_subscribers(cred));
174
175	BUG_ON(atomic_read(&cred->usage) != 0);
176#ifdef CONFIG_DEBUG_CREDENTIALS
177	BUG_ON(read_cred_subscribers(cred) != 0);
178	cred->magic = CRED_MAGIC_DEAD;
179	cred->put_addr = __builtin_return_address(0);
180#endif
181	BUG_ON(cred == current->cred);
182	BUG_ON(cred == current->real_cred);
183
184	call_rcu(&cred->rcu, put_cred_rcu);
 
 
 
185}
186EXPORT_SYMBOL(__put_cred);
187
188/*
189 * Clean up a task's credentials when it exits
190 */
191void exit_creds(struct task_struct *tsk)
192{
193	struct cred *cred;
194
195	kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
196	       atomic_read(&tsk->cred->usage),
197	       read_cred_subscribers(tsk->cred));
198
199	cred = (struct cred *) tsk->real_cred;
200	tsk->real_cred = NULL;
201	validate_creds(cred);
202	alter_cred_subscribers(cred, -1);
203	put_cred(cred);
204
205	cred = (struct cred *) tsk->cred;
206	tsk->cred = NULL;
207	validate_creds(cred);
208	alter_cred_subscribers(cred, -1);
209	put_cred(cred);
 
 
 
 
 
 
 
 
 
210}
211
212/**
213 * get_task_cred - Get another task's objective credentials
214 * @task: The task to query
215 *
216 * Get the objective credentials of a task, pinning them so that they can't go
217 * away.  Accessing a task's credentials directly is not permitted.
218 *
219 * The caller must also make sure task doesn't get deleted, either by holding a
220 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
221 */
222const struct cred *get_task_cred(struct task_struct *task)
223{
224	const struct cred *cred;
225
226	rcu_read_lock();
227
228	do {
229		cred = __task_cred((task));
230		BUG_ON(!cred);
231	} while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
232
233	rcu_read_unlock();
234	return cred;
235}
 
236
237/*
238 * Allocate blank credentials, such that the credentials can be filled in at a
239 * later date without risk of ENOMEM.
240 */
241struct cred *cred_alloc_blank(void)
242{
243	struct cred *new;
244
245	new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
246	if (!new)
247		return NULL;
248
249#ifdef CONFIG_KEYS
250	new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
251	if (!new->tgcred) {
252		kmem_cache_free(cred_jar, new);
253		return NULL;
254	}
255	atomic_set(&new->tgcred->usage, 1);
256#endif
257
258	atomic_set(&new->usage, 1);
259#ifdef CONFIG_DEBUG_CREDENTIALS
260	new->magic = CRED_MAGIC;
261#endif
262
263	if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
264		goto error;
265
266	return new;
267
268error:
269	abort_creds(new);
270	return NULL;
271}
272
273/**
274 * prepare_creds - Prepare a new set of credentials for modification
275 *
276 * Prepare a new set of task credentials for modification.  A task's creds
277 * shouldn't generally be modified directly, therefore this function is used to
278 * prepare a new copy, which the caller then modifies and then commits by
279 * calling commit_creds().
280 *
281 * Preparation involves making a copy of the objective creds for modification.
282 *
283 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
284 *
285 * Call commit_creds() or abort_creds() to clean up.
286 */
287struct cred *prepare_creds(void)
288{
289	struct task_struct *task = current;
290	const struct cred *old;
291	struct cred *new;
292
293	validate_process_creds();
294
295	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
296	if (!new)
297		return NULL;
298
299	kdebug("prepare_creds() alloc %p", new);
300
301	old = task->cred;
302	memcpy(new, old, sizeof(struct cred));
303
304	atomic_set(&new->usage, 1);
305	set_cred_subscribers(new, 0);
306	get_group_info(new->group_info);
307	get_uid(new->user);
308	get_user_ns(new->user_ns);
309
310#ifdef CONFIG_KEYS
 
 
311	key_get(new->thread_keyring);
312	key_get(new->request_key_auth);
313	atomic_inc(&new->tgcred->usage);
314#endif
315
316#ifdef CONFIG_SECURITY
317	new->security = NULL;
318#endif
319
320	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 
321		goto error;
322	validate_creds(new);
 
 
 
323	return new;
324
325error:
326	abort_creds(new);
327	return NULL;
328}
329EXPORT_SYMBOL(prepare_creds);
330
331/*
332 * Prepare credentials for current to perform an execve()
333 * - The caller must hold ->cred_guard_mutex
334 */
335struct cred *prepare_exec_creds(void)
336{
337	struct thread_group_cred *tgcred = NULL;
338	struct cred *new;
339
340#ifdef CONFIG_KEYS
341	tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
342	if (!tgcred)
343		return NULL;
344#endif
345
346	new = prepare_creds();
347	if (!new) {
348		kfree(tgcred);
349		return new;
350	}
351
352#ifdef CONFIG_KEYS
353	/* newly exec'd tasks don't get a thread keyring */
354	key_put(new->thread_keyring);
355	new->thread_keyring = NULL;
356
357	/* create a new per-thread-group creds for all this set of threads to
358	 * share */
359	memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
360
361	atomic_set(&tgcred->usage, 1);
362	spin_lock_init(&tgcred->lock);
363
364	/* inherit the session keyring; new process keyring */
365	key_get(tgcred->session_keyring);
366	tgcred->process_keyring = NULL;
367
368	release_tgcred(new);
369	new->tgcred = tgcred;
370#endif
371
 
 
 
372	return new;
373}
374
375/*
376 * Copy credentials for the new process created by fork()
377 *
378 * We share if we can, but under some circumstances we have to generate a new
379 * set.
380 *
381 * The new process gets the current process's subjective credentials as its
382 * objective and subjective credentials
383 */
384int copy_creds(struct task_struct *p, unsigned long clone_flags)
385{
386#ifdef CONFIG_KEYS
387	struct thread_group_cred *tgcred;
388#endif
389	struct cred *new;
390	int ret;
391
 
 
 
 
392	if (
393#ifdef CONFIG_KEYS
394		!p->cred->thread_keyring &&
395#endif
396		clone_flags & CLONE_THREAD
397	    ) {
398		p->real_cred = get_cred(p->cred);
399		get_cred(p->cred);
400		alter_cred_subscribers(p->cred, 2);
401		kdebug("share_creds(%p{%d,%d})",
402		       p->cred, atomic_read(&p->cred->usage),
403		       read_cred_subscribers(p->cred));
404		atomic_inc(&p->cred->user->processes);
405		return 0;
406	}
407
408	new = prepare_creds();
409	if (!new)
410		return -ENOMEM;
411
412	if (clone_flags & CLONE_NEWUSER) {
413		ret = create_user_ns(new);
414		if (ret < 0)
415			goto error_put;
 
 
 
416	}
417
418#ifdef CONFIG_KEYS
419	/* new threads get their own thread keyrings if their parent already
420	 * had one */
421	if (new->thread_keyring) {
422		key_put(new->thread_keyring);
423		new->thread_keyring = NULL;
424		if (clone_flags & CLONE_THREAD)
425			install_thread_keyring_to_cred(new);
426	}
427
428	/* we share the process and session keyrings between all the threads in
429	 * a process - this is slightly icky as we violate COW credentials a
430	 * bit */
431	if (!(clone_flags & CLONE_THREAD)) {
432		tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
433		if (!tgcred) {
434			ret = -ENOMEM;
435			goto error_put;
436		}
437		atomic_set(&tgcred->usage, 1);
438		spin_lock_init(&tgcred->lock);
439		tgcred->process_keyring = NULL;
440		tgcred->session_keyring = key_get(new->tgcred->session_keyring);
441
442		release_tgcred(new);
443		new->tgcred = tgcred;
444	}
445#endif
446
447	atomic_inc(&new->user->processes);
448	p->cred = p->real_cred = get_cred(new);
449	alter_cred_subscribers(new, 2);
450	validate_creds(new);
451	return 0;
452
453error_put:
454	put_cred(new);
455	return ret;
456}
457
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
458/**
459 * commit_creds - Install new credentials upon the current task
460 * @new: The credentials to be assigned
461 *
462 * Install a new set of credentials to the current task, using RCU to replace
463 * the old set.  Both the objective and the subjective credentials pointers are
464 * updated.  This function may not be called if the subjective credentials are
465 * in an overridden state.
466 *
467 * This function eats the caller's reference to the new credentials.
468 *
469 * Always returns 0 thus allowing this function to be tail-called at the end
470 * of, say, sys_setgid().
471 */
472int commit_creds(struct cred *new)
473{
474	struct task_struct *task = current;
475	const struct cred *old = task->real_cred;
476
477	kdebug("commit_creds(%p{%d,%d})", new,
478	       atomic_read(&new->usage),
479	       read_cred_subscribers(new));
480
481	BUG_ON(task->cred != old);
482#ifdef CONFIG_DEBUG_CREDENTIALS
483	BUG_ON(read_cred_subscribers(old) < 2);
484	validate_creds(old);
485	validate_creds(new);
486#endif
487	BUG_ON(atomic_read(&new->usage) < 1);
488
489	get_cred(new); /* we will require a ref for the subj creds too */
490
491	/* dumpability changes */
492	if (!uid_eq(old->euid, new->euid) ||
493	    !gid_eq(old->egid, new->egid) ||
494	    !uid_eq(old->fsuid, new->fsuid) ||
495	    !gid_eq(old->fsgid, new->fsgid) ||
496	    !cap_issubset(new->cap_permitted, old->cap_permitted)) {
497		if (task->mm)
498			set_dumpable(task->mm, suid_dumpable);
499		task->pdeath_signal = 0;
 
 
 
 
 
 
 
 
 
500		smp_wmb();
501	}
502
503	/* alter the thread keyring */
504	if (!uid_eq(new->fsuid, old->fsuid))
505		key_fsuid_changed(task);
506	if (!gid_eq(new->fsgid, old->fsgid))
507		key_fsgid_changed(task);
508
509	/* do it
510	 * RLIMIT_NPROC limits on user->processes have already been checked
511	 * in set_user().
512	 */
513	alter_cred_subscribers(new, 2);
514	if (new->user != old->user)
515		atomic_inc(&new->user->processes);
516	rcu_assign_pointer(task->real_cred, new);
517	rcu_assign_pointer(task->cred, new);
518	if (new->user != old->user)
519		atomic_dec(&old->user->processes);
520	alter_cred_subscribers(old, -2);
521
522	/* send notifications */
523	if (!uid_eq(new->uid,   old->uid)  ||
524	    !uid_eq(new->euid,  old->euid) ||
525	    !uid_eq(new->suid,  old->suid) ||
526	    !uid_eq(new->fsuid, old->fsuid))
527		proc_id_connector(task, PROC_EVENT_UID);
528
529	if (!gid_eq(new->gid,   old->gid)  ||
530	    !gid_eq(new->egid,  old->egid) ||
531	    !gid_eq(new->sgid,  old->sgid) ||
532	    !gid_eq(new->fsgid, old->fsgid))
533		proc_id_connector(task, PROC_EVENT_GID);
534
535	/* release the old obj and subj refs both */
536	put_cred(old);
537	put_cred(old);
538	return 0;
539}
540EXPORT_SYMBOL(commit_creds);
541
542/**
543 * abort_creds - Discard a set of credentials and unlock the current task
544 * @new: The credentials that were going to be applied
545 *
546 * Discard a set of credentials that were under construction and unlock the
547 * current task.
548 */
549void abort_creds(struct cred *new)
550{
551	kdebug("abort_creds(%p{%d,%d})", new,
552	       atomic_read(&new->usage),
553	       read_cred_subscribers(new));
554
555#ifdef CONFIG_DEBUG_CREDENTIALS
556	BUG_ON(read_cred_subscribers(new) != 0);
557#endif
558	BUG_ON(atomic_read(&new->usage) < 1);
559	put_cred(new);
560}
561EXPORT_SYMBOL(abort_creds);
562
563/**
564 * override_creds - Override the current process's subjective credentials
565 * @new: The credentials to be assigned
566 *
567 * Install a set of temporary override subjective credentials on the current
568 * process, returning the old set for later reversion.
569 */
570const struct cred *override_creds(const struct cred *new)
571{
572	const struct cred *old = current->cred;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
573
574	kdebug("override_creds(%p{%d,%d})", new,
575	       atomic_read(&new->usage),
576	       read_cred_subscribers(new));
577
578	validate_creds(old);
579	validate_creds(new);
580	get_cred(new);
581	alter_cred_subscribers(new, 1);
582	rcu_assign_pointer(current->cred, new);
583	alter_cred_subscribers(old, -1);
584
585	kdebug("override_creds() = %p{%d,%d}", old,
586	       atomic_read(&old->usage),
587	       read_cred_subscribers(old));
588	return old;
589}
590EXPORT_SYMBOL(override_creds);
591
592/**
593 * revert_creds - Revert a temporary subjective credentials override
594 * @old: The credentials to be restored
595 *
596 * Revert a temporary set of override subjective credentials to an old set,
597 * discarding the override set.
598 */
599void revert_creds(const struct cred *old)
600{
601	const struct cred *override = current->cred;
602
603	kdebug("revert_creds(%p{%d,%d})", old,
604	       atomic_read(&old->usage),
605	       read_cred_subscribers(old));
606
607	validate_creds(old);
608	validate_creds(override);
609	alter_cred_subscribers(old, 1);
610	rcu_assign_pointer(current->cred, old);
611	alter_cred_subscribers(override, -1);
612	put_cred(override);
613}
614EXPORT_SYMBOL(revert_creds);
615
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
616/*
617 * initialise the credentials stuff
618 */
619void __init cred_init(void)
620{
621	/* allocate a slab in which we can store credentials */
622	cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
623				     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
624}
625
626/**
627 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
628 * @daemon: A userspace daemon to be used as a reference
629 *
630 * Prepare a set of credentials for a kernel service.  This can then be used to
631 * override a task's own credentials so that work can be done on behalf of that
632 * task that requires a different subjective context.
633 *
634 * @daemon is used to provide a base for the security record, but can be NULL.
635 * If @daemon is supplied, then the security data will be derived from that;
636 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
637 *
638 * The caller may change these controls afterwards if desired.
639 *
640 * Returns the new credentials or NULL if out of memory.
641 *
642 * Does not take, and does not return holding current->cred_replace_mutex.
643 */
644struct cred *prepare_kernel_cred(struct task_struct *daemon)
645{
646#ifdef CONFIG_KEYS
647	struct thread_group_cred *tgcred;
648#endif
649	const struct cred *old;
650	struct cred *new;
651
652	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
653	if (!new)
654		return NULL;
655
656#ifdef CONFIG_KEYS
657	tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
658	if (!tgcred) {
659		kmem_cache_free(cred_jar, new);
660		return NULL;
661	}
662#endif
663
664	kdebug("prepare_kernel_cred() alloc %p", new);
665
666	if (daemon)
667		old = get_task_cred(daemon);
668	else
669		old = get_cred(&init_cred);
670
671	validate_creds(old);
672
673	*new = *old;
674	atomic_set(&new->usage, 1);
675	set_cred_subscribers(new, 0);
676	get_uid(new->user);
677	get_user_ns(new->user_ns);
678	get_group_info(new->group_info);
679
680#ifdef CONFIG_KEYS
681	atomic_set(&tgcred->usage, 1);
682	spin_lock_init(&tgcred->lock);
683	tgcred->process_keyring = NULL;
684	tgcred->session_keyring = NULL;
685	new->tgcred = tgcred;
686	new->request_key_auth = NULL;
687	new->thread_keyring = NULL;
 
688	new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
689#endif
690
691#ifdef CONFIG_SECURITY
692	new->security = NULL;
693#endif
694	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 
 
 
 
695		goto error;
696
697	put_cred(old);
698	validate_creds(new);
699	return new;
700
701error:
702	put_cred(new);
703	put_cred(old);
704	return NULL;
705}
706EXPORT_SYMBOL(prepare_kernel_cred);
707
708/**
709 * set_security_override - Set the security ID in a set of credentials
710 * @new: The credentials to alter
711 * @secid: The LSM security ID to set
712 *
713 * Set the LSM security ID in a set of credentials so that the subjective
714 * security is overridden when an alternative set of credentials is used.
715 */
716int set_security_override(struct cred *new, u32 secid)
717{
718	return security_kernel_act_as(new, secid);
719}
720EXPORT_SYMBOL(set_security_override);
721
722/**
723 * set_security_override_from_ctx - Set the security ID in a set of credentials
724 * @new: The credentials to alter
725 * @secctx: The LSM security context to generate the security ID from.
726 *
727 * Set the LSM security ID in a set of credentials so that the subjective
728 * security is overridden when an alternative set of credentials is used.  The
729 * security ID is specified in string form as a security context to be
730 * interpreted by the LSM.
731 */
732int set_security_override_from_ctx(struct cred *new, const char *secctx)
733{
734	u32 secid;
735	int ret;
736
737	ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
738	if (ret < 0)
739		return ret;
740
741	return set_security_override(new, secid);
742}
743EXPORT_SYMBOL(set_security_override_from_ctx);
744
745/**
746 * set_create_files_as - Set the LSM file create context in a set of credentials
747 * @new: The credentials to alter
748 * @inode: The inode to take the context from
749 *
750 * Change the LSM file creation context in a set of credentials to be the same
751 * as the object context of the specified inode, so that the new inodes have
752 * the same MAC context as that inode.
753 */
754int set_create_files_as(struct cred *new, struct inode *inode)
755{
 
 
756	new->fsuid = inode->i_uid;
757	new->fsgid = inode->i_gid;
758	return security_kernel_create_files_as(new, inode);
759}
760EXPORT_SYMBOL(set_create_files_as);
761
762#ifdef CONFIG_DEBUG_CREDENTIALS
763
764bool creds_are_invalid(const struct cred *cred)
765{
766	if (cred->magic != CRED_MAGIC)
767		return true;
768#ifdef CONFIG_SECURITY_SELINUX
769	/*
770	 * cred->security == NULL if security_cred_alloc_blank() or
771	 * security_prepare_creds() returned an error.
772	 */
773	if (selinux_is_enabled() && cred->security) {
774		if ((unsigned long) cred->security < PAGE_SIZE)
775			return true;
776		if ((*(u32 *)cred->security & 0xffffff00) ==
777		    (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
778			return true;
779	}
780#endif
781	return false;
782}
783EXPORT_SYMBOL(creds_are_invalid);
784
785/*
786 * dump invalid credentials
787 */
788static void dump_invalid_creds(const struct cred *cred, const char *label,
789			       const struct task_struct *tsk)
790{
791	printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
792	       label, cred,
793	       cred == &init_cred ? "[init]" : "",
794	       cred == tsk->real_cred ? "[real]" : "",
795	       cred == tsk->cred ? "[eff]" : "");
796	printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
797	       cred->magic, cred->put_addr);
798	printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
799	       atomic_read(&cred->usage),
800	       read_cred_subscribers(cred));
801	printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
802	       cred->uid, cred->euid, cred->suid, cred->fsuid);
803	printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
804	       cred->gid, cred->egid, cred->sgid, cred->fsgid);
805#ifdef CONFIG_SECURITY
806	printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
807	if ((unsigned long) cred->security >= PAGE_SIZE &&
808	    (((unsigned long) cred->security & 0xffffff00) !=
809	     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
810		printk(KERN_ERR "CRED: ->security {%x, %x}\n",
811		       ((u32*)cred->security)[0],
812		       ((u32*)cred->security)[1]);
813#endif
814}
815
816/*
817 * report use of invalid credentials
818 */
819void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
820{
821	printk(KERN_ERR "CRED: Invalid credentials\n");
822	printk(KERN_ERR "CRED: At %s:%u\n", file, line);
823	dump_invalid_creds(cred, "Specified", current);
824	BUG();
825}
826EXPORT_SYMBOL(__invalid_creds);
827
828/*
829 * check the credentials on a process
830 */
831void __validate_process_creds(struct task_struct *tsk,
832			      const char *file, unsigned line)
833{
834	if (tsk->cred == tsk->real_cred) {
835		if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
836			     creds_are_invalid(tsk->cred)))
837			goto invalid_creds;
838	} else {
839		if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
840			     read_cred_subscribers(tsk->cred) < 1 ||
841			     creds_are_invalid(tsk->real_cred) ||
842			     creds_are_invalid(tsk->cred)))
843			goto invalid_creds;
844	}
845	return;
846
847invalid_creds:
848	printk(KERN_ERR "CRED: Invalid process credentials\n");
849	printk(KERN_ERR "CRED: At %s:%u\n", file, line);
850
851	dump_invalid_creds(tsk->real_cred, "Real", tsk);
852	if (tsk->cred != tsk->real_cred)
853		dump_invalid_creds(tsk->cred, "Effective", tsk);
854	else
855		printk(KERN_ERR "CRED: Effective creds == Real creds\n");
856	BUG();
857}
858EXPORT_SYMBOL(__validate_process_creds);
859
860/*
861 * check creds for do_exit()
862 */
863void validate_creds_for_do_exit(struct task_struct *tsk)
864{
865	kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
866	       tsk->real_cred, tsk->cred,
867	       atomic_read(&tsk->cred->usage),
868	       read_cred_subscribers(tsk->cred));
869
870	__validate_process_creds(tsk, __FILE__, __LINE__);
871}
872
873#endif /* CONFIG_DEBUG_CREDENTIALS */