1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* Task credentials management - see Documentation/security/credentials.rst
  3 *
  4 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
  5 * Written by David Howells (dhowells@redhat.com)
  6 */
  7#include <linux/export.h>
  8#include <linux/cred.h>
  9#include <linux/slab.h>
 10#include <linux/sched.h>
 11#include <linux/sched/coredump.h>
 12#include <linux/key.h>
 13#include <linux/keyctl.h>
 14#include <linux/init_task.h>
 15#include <linux/security.h>
 16#include <linux/binfmts.h>
 17#include <linux/cn_proc.h>
 18#include <linux/uidgid.h>
 19
 20#if 0
 21#define kdebug(FMT, ...)						\
 22	printk("[%-5.5s%5u] " FMT "\n",					\
 23	       current->comm, current->pid, ##__VA_ARGS__)
 24#else
 25#define kdebug(FMT, ...)						\
 26do {									\
 27	if (0)								\
 28		no_printk("[%-5.5s%5u] " FMT "\n",			\
 29			  current->comm, current->pid, ##__VA_ARGS__);	\
 30} while (0)
 31#endif
 32
 33static struct kmem_cache *cred_jar;
 34
 35/* init to 2 - one for init_task, one to ensure it is never freed */
 36struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
 37
 38/*
 39 * The initial credentials for the initial task
 40 */
 41struct cred init_cred = {
 42	.usage			= ATOMIC_INIT(4),
 43#ifdef CONFIG_DEBUG_CREDENTIALS
 44	.subscribers		= ATOMIC_INIT(2),
 45	.magic			= CRED_MAGIC,
 46#endif
 47	.uid			= GLOBAL_ROOT_UID,
 48	.gid			= GLOBAL_ROOT_GID,
 49	.suid			= GLOBAL_ROOT_UID,
 50	.sgid			= GLOBAL_ROOT_GID,
 51	.euid			= GLOBAL_ROOT_UID,
 52	.egid			= GLOBAL_ROOT_GID,
 53	.fsuid			= GLOBAL_ROOT_UID,
 54	.fsgid			= GLOBAL_ROOT_GID,
 55	.securebits		= SECUREBITS_DEFAULT,
 56	.cap_inheritable	= CAP_EMPTY_SET,
 57	.cap_permitted		= CAP_FULL_SET,
 58	.cap_effective		= CAP_FULL_SET,
 59	.cap_bset		= CAP_FULL_SET,
 60	.user			= INIT_USER,
 61	.user_ns		= &init_user_ns,
 62	.group_info		= &init_groups,
 63};
 64
 65static inline void set_cred_subscribers(struct cred *cred, int n)
 66{
 67#ifdef CONFIG_DEBUG_CREDENTIALS
 68	atomic_set(&cred->subscribers, n);
 69#endif
 70}
 71
 72static inline int read_cred_subscribers(const struct cred *cred)
 73{
 74#ifdef CONFIG_DEBUG_CREDENTIALS
 75	return atomic_read(&cred->subscribers);
 76#else
 77	return 0;
 78#endif
 79}
 80
 81static inline void alter_cred_subscribers(const struct cred *_cred, int n)
 82{
 83#ifdef CONFIG_DEBUG_CREDENTIALS
 84	struct cred *cred = (struct cred *) _cred;
 85
 86	atomic_add(n, &cred->subscribers);
 87#endif
 88}
 89
 90/*
 91 * The RCU callback to actually dispose of a set of credentials
 92 */
 93static void put_cred_rcu(struct rcu_head *rcu)
 94{
 95	struct cred *cred = container_of(rcu, struct cred, rcu);
 96
 97	kdebug("put_cred_rcu(%p)", cred);
 98
 99#ifdef CONFIG_DEBUG_CREDENTIALS
100	if (cred->magic != CRED_MAGIC_DEAD ||
101	    atomic_read(&cred->usage) != 0 ||
102	    read_cred_subscribers(cred) != 0)
103		panic("CRED: put_cred_rcu() sees %p with"
104		      " mag %x, put %p, usage %d, subscr %d\n",
105		      cred, cred->magic, cred->put_addr,
106		      atomic_read(&cred->usage),
107		      read_cred_subscribers(cred));
108#else
109	if (atomic_read(&cred->usage) != 0)
110		panic("CRED: put_cred_rcu() sees %p with usage %d\n",
111		      cred, atomic_read(&cred->usage));
112#endif
113
114	security_cred_free(cred);
115	key_put(cred->session_keyring);
116	key_put(cred->process_keyring);
117	key_put(cred->thread_keyring);
118	key_put(cred->request_key_auth);
119	if (cred->group_info)
120		put_group_info(cred->group_info);
121	free_uid(cred->user);
122	put_user_ns(cred->user_ns);
123	kmem_cache_free(cred_jar, cred);
124}
125
126/**
127 * __put_cred - Destroy a set of credentials
128 * @cred: The record to release
129 *
130 * Destroy a set of credentials on which no references remain.
131 */
132void __put_cred(struct cred *cred)
133{
134	kdebug("__put_cred(%p{%d,%d})", cred,
135	       atomic_read(&cred->usage),
136	       read_cred_subscribers(cred));
137
138	BUG_ON(atomic_read(&cred->usage) != 0);
139#ifdef CONFIG_DEBUG_CREDENTIALS
140	BUG_ON(read_cred_subscribers(cred) != 0);
141	cred->magic = CRED_MAGIC_DEAD;
142	cred->put_addr = __builtin_return_address(0);
143#endif
144	BUG_ON(cred == current->cred);
145	BUG_ON(cred == current->real_cred);
146
147	if (cred->non_rcu)
148		put_cred_rcu(&cred->rcu);
149	else
150		call_rcu(&cred->rcu, put_cred_rcu);
151}
152EXPORT_SYMBOL(__put_cred);
153
154/*
155 * Clean up a task's credentials when it exits
156 */
157void exit_creds(struct task_struct *tsk)
158{
159	struct cred *cred;
160
161	kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
162	       atomic_read(&tsk->cred->usage),
163	       read_cred_subscribers(tsk->cred));
164
165	cred = (struct cred *) tsk->real_cred;
166	tsk->real_cred = NULL;
167	validate_creds(cred);
168	alter_cred_subscribers(cred, -1);
169	put_cred(cred);
170
171	cred = (struct cred *) tsk->cred;
172	tsk->cred = NULL;
173	validate_creds(cred);
174	alter_cred_subscribers(cred, -1);
175	put_cred(cred);
176
177#ifdef CONFIG_KEYS_REQUEST_CACHE
178	key_put(current->cached_requested_key);
179	current->cached_requested_key = NULL;
180#endif
181}
182
183/**
184 * get_task_cred - Get another task's objective credentials
185 * @task: The task to query
186 *
187 * Get the objective credentials of a task, pinning them so that they can't go
188 * away.  Accessing a task's credentials directly is not permitted.
189 *
190 * The caller must also make sure task doesn't get deleted, either by holding a
191 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
192 */
193const struct cred *get_task_cred(struct task_struct *task)
194{
195	const struct cred *cred;
196
197	rcu_read_lock();
198
199	do {
200		cred = __task_cred((task));
201		BUG_ON(!cred);
202	} while (!get_cred_rcu(cred));
203
204	rcu_read_unlock();
205	return cred;
206}
207EXPORT_SYMBOL(get_task_cred);
208
209/*
210 * Allocate blank credentials, such that the credentials can be filled in at a
211 * later date without risk of ENOMEM.
212 */
213struct cred *cred_alloc_blank(void)
214{
215	struct cred *new;
216
217	new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
218	if (!new)
219		return NULL;
220
221	atomic_set(&new->usage, 1);
222#ifdef CONFIG_DEBUG_CREDENTIALS
223	new->magic = CRED_MAGIC;
224#endif
225
226	if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
227		goto error;
228
229	return new;
230
231error:
232	abort_creds(new);
233	return NULL;
234}
235
236/**
237 * prepare_creds - Prepare a new set of credentials for modification
238 *
239 * Prepare a new set of task credentials for modification.  A task's creds
240 * shouldn't generally be modified directly, therefore this function is used to
241 * prepare a new copy, which the caller then modifies and then commits by
242 * calling commit_creds().
243 *
244 * Preparation involves making a copy of the objective creds for modification.
245 *
246 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
247 *
248 * Call commit_creds() or abort_creds() to clean up.
249 */
250struct cred *prepare_creds(void)
251{
252	struct task_struct *task = current;
253	const struct cred *old;
254	struct cred *new;
255
256	validate_process_creds();
257
258	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
259	if (!new)
260		return NULL;
261
262	kdebug("prepare_creds() alloc %p", new);
263
264	old = task->cred;
265	memcpy(new, old, sizeof(struct cred));
266
267	new->non_rcu = 0;
268	atomic_set(&new->usage, 1);
269	set_cred_subscribers(new, 0);
270	get_group_info(new->group_info);
271	get_uid(new->user);
272	get_user_ns(new->user_ns);
273
274#ifdef CONFIG_KEYS
275	key_get(new->session_keyring);
276	key_get(new->process_keyring);
277	key_get(new->thread_keyring);
278	key_get(new->request_key_auth);
279#endif
280
281#ifdef CONFIG_SECURITY
282	new->security = NULL;
283#endif
284
285	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
286		goto error;
287	validate_creds(new);
288	return new;
289
290error:
291	abort_creds(new);
292	return NULL;
293}
294EXPORT_SYMBOL(prepare_creds);
295
296/*
297 * Prepare credentials for current to perform an execve()
298 * - The caller must hold ->cred_guard_mutex
299 */
300struct cred *prepare_exec_creds(void)
301{
302	struct cred *new;
303
304	new = prepare_creds();
305	if (!new)
306		return new;
307
308#ifdef CONFIG_KEYS
309	/* newly exec'd tasks don't get a thread keyring */
310	key_put(new->thread_keyring);
311	new->thread_keyring = NULL;
312
313	/* inherit the session keyring; new process keyring */
314	key_put(new->process_keyring);
315	new->process_keyring = NULL;
316#endif
317
 
 
 
318	return new;
319}
320
321/*
322 * Copy credentials for the new process created by fork()
323 *
324 * We share if we can, but under some circumstances we have to generate a new
325 * set.
326 *
327 * The new process gets the current process's subjective credentials as its
328 * objective and subjective credentials
329 */
330int copy_creds(struct task_struct *p, unsigned long clone_flags)
331{
332	struct cred *new;
333	int ret;
334
335#ifdef CONFIG_KEYS_REQUEST_CACHE
336	p->cached_requested_key = NULL;
337#endif
338
339	if (
340#ifdef CONFIG_KEYS
341		!p->cred->thread_keyring &&
342#endif
343		clone_flags & CLONE_THREAD
344	    ) {
345		p->real_cred = get_cred(p->cred);
346		get_cred(p->cred);
347		alter_cred_subscribers(p->cred, 2);
348		kdebug("share_creds(%p{%d,%d})",
349		       p->cred, atomic_read(&p->cred->usage),
350		       read_cred_subscribers(p->cred));
351		atomic_inc(&p->cred->user->processes);
352		return 0;
353	}
354
355	new = prepare_creds();
356	if (!new)
357		return -ENOMEM;
358
359	if (clone_flags & CLONE_NEWUSER) {
360		ret = create_user_ns(new);
361		if (ret < 0)
362			goto error_put;
363	}
364
365#ifdef CONFIG_KEYS
366	/* new threads get their own thread keyrings if their parent already
367	 * had one */
368	if (new->thread_keyring) {
369		key_put(new->thread_keyring);
370		new->thread_keyring = NULL;
371		if (clone_flags & CLONE_THREAD)
372			install_thread_keyring_to_cred(new);
373	}
374
375	/* The process keyring is only shared between the threads in a process;
376	 * anything outside of those threads doesn't inherit.
377	 */
378	if (!(clone_flags & CLONE_THREAD)) {
379		key_put(new->process_keyring);
380		new->process_keyring = NULL;
381	}
382#endif
383
384	atomic_inc(&new->user->processes);
385	p->cred = p->real_cred = get_cred(new);
386	alter_cred_subscribers(new, 2);
387	validate_creds(new);
388	return 0;
389
390error_put:
391	put_cred(new);
392	return ret;
393}
394
395static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
396{
397	const struct user_namespace *set_ns = set->user_ns;
398	const struct user_namespace *subset_ns = subset->user_ns;
399
400	/* If the two credentials are in the same user namespace see if
401	 * the capabilities of subset are a subset of set.
402	 */
403	if (set_ns == subset_ns)
404		return cap_issubset(subset->cap_permitted, set->cap_permitted);
405
406	/* The credentials are in a different user namespaces
407	 * therefore one is a subset of the other only if a set is an
408	 * ancestor of subset and set->euid is owner of subset or one
409	 * of subsets ancestors.
410	 */
411	for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
412		if ((set_ns == subset_ns->parent)  &&
413		    uid_eq(subset_ns->owner, set->euid))
414			return true;
415	}
416
417	return false;
418}
419
420/**
421 * commit_creds - Install new credentials upon the current task
422 * @new: The credentials to be assigned
423 *
424 * Install a new set of credentials to the current task, using RCU to replace
425 * the old set.  Both the objective and the subjective credentials pointers are
426 * updated.  This function may not be called if the subjective credentials are
427 * in an overridden state.
428 *
429 * This function eats the caller's reference to the new credentials.
430 *
431 * Always returns 0 thus allowing this function to be tail-called at the end
432 * of, say, sys_setgid().
433 */
434int commit_creds(struct cred *new)
435{
436	struct task_struct *task = current;
437	const struct cred *old = task->real_cred;
438
439	kdebug("commit_creds(%p{%d,%d})", new,
440	       atomic_read(&new->usage),
441	       read_cred_subscribers(new));
442
443	BUG_ON(task->cred != old);
444#ifdef CONFIG_DEBUG_CREDENTIALS
445	BUG_ON(read_cred_subscribers(old) < 2);
446	validate_creds(old);
447	validate_creds(new);
448#endif
449	BUG_ON(atomic_read(&new->usage) < 1);
450
451	get_cred(new); /* we will require a ref for the subj creds too */
452
453	/* dumpability changes */
454	if (!uid_eq(old->euid, new->euid) ||
455	    !gid_eq(old->egid, new->egid) ||
456	    !uid_eq(old->fsuid, new->fsuid) ||
457	    !gid_eq(old->fsgid, new->fsgid) ||
458	    !cred_cap_issubset(old, new)) {
459		if (task->mm)
460			set_dumpable(task->mm, suid_dumpable);
461		task->pdeath_signal = 0;
462		/*
463		 * If a task drops privileges and becomes nondumpable,
464		 * the dumpability change must become visible before
465		 * the credential change; otherwise, a __ptrace_may_access()
466		 * racing with this change may be able to attach to a task it
467		 * shouldn't be able to attach to (as if the task had dropped
468		 * privileges without becoming nondumpable).
469		 * Pairs with a read barrier in __ptrace_may_access().
470		 */
471		smp_wmb();
472	}
473
474	/* alter the thread keyring */
475	if (!uid_eq(new->fsuid, old->fsuid))
476		key_fsuid_changed(new);
477	if (!gid_eq(new->fsgid, old->fsgid))
478		key_fsgid_changed(new);
479
480	/* do it
481	 * RLIMIT_NPROC limits on user->processes have already been checked
482	 * in set_user().
483	 */
484	alter_cred_subscribers(new, 2);
485	if (new->user != old->user)
486		atomic_inc(&new->user->processes);
487	rcu_assign_pointer(task->real_cred, new);
488	rcu_assign_pointer(task->cred, new);
489	if (new->user != old->user)
490		atomic_dec(&old->user->processes);
491	alter_cred_subscribers(old, -2);
492
493	/* send notifications */
494	if (!uid_eq(new->uid,   old->uid)  ||
495	    !uid_eq(new->euid,  old->euid) ||
496	    !uid_eq(new->suid,  old->suid) ||
497	    !uid_eq(new->fsuid, old->fsuid))
498		proc_id_connector(task, PROC_EVENT_UID);
499
500	if (!gid_eq(new->gid,   old->gid)  ||
501	    !gid_eq(new->egid,  old->egid) ||
502	    !gid_eq(new->sgid,  old->sgid) ||
503	    !gid_eq(new->fsgid, old->fsgid))
504		proc_id_connector(task, PROC_EVENT_GID);
505
506	/* release the old obj and subj refs both */
507	put_cred(old);
508	put_cred(old);
509	return 0;
510}
511EXPORT_SYMBOL(commit_creds);
512
513/**
514 * abort_creds - Discard a set of credentials and unlock the current task
515 * @new: The credentials that were going to be applied
516 *
517 * Discard a set of credentials that were under construction and unlock the
518 * current task.
519 */
520void abort_creds(struct cred *new)
521{
522	kdebug("abort_creds(%p{%d,%d})", new,
523	       atomic_read(&new->usage),
524	       read_cred_subscribers(new));
525
526#ifdef CONFIG_DEBUG_CREDENTIALS
527	BUG_ON(read_cred_subscribers(new) != 0);
528#endif
529	BUG_ON(atomic_read(&new->usage) < 1);
530	put_cred(new);
531}
532EXPORT_SYMBOL(abort_creds);
533
534/**
535 * override_creds - Override the current process's subjective credentials
536 * @new: The credentials to be assigned
537 *
538 * Install a set of temporary override subjective credentials on the current
539 * process, returning the old set for later reversion.
540 */
541const struct cred *override_creds(const struct cred *new)
542{
543	const struct cred *old = current->cred;
544
545	kdebug("override_creds(%p{%d,%d})", new,
546	       atomic_read(&new->usage),
547	       read_cred_subscribers(new));
548
549	validate_creds(old);
550	validate_creds(new);
551
552	/*
553	 * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
554	 *
555	 * That means that we do not clear the 'non_rcu' flag, since
556	 * we are only installing the cred into the thread-synchronous
557	 * '->cred' pointer, not the '->real_cred' pointer that is
558	 * visible to other threads under RCU.
559	 *
560	 * Also note that we did validate_creds() manually, not depending
561	 * on the validation in 'get_cred()'.
562	 */
563	get_new_cred((struct cred *)new);
564	alter_cred_subscribers(new, 1);
565	rcu_assign_pointer(current->cred, new);
566	alter_cred_subscribers(old, -1);
567
568	kdebug("override_creds() = %p{%d,%d}", old,
569	       atomic_read(&old->usage),
570	       read_cred_subscribers(old));
571	return old;
572}
573EXPORT_SYMBOL(override_creds);
574
575/**
576 * revert_creds - Revert a temporary subjective credentials override
577 * @old: The credentials to be restored
578 *
579 * Revert a temporary set of override subjective credentials to an old set,
580 * discarding the override set.
581 */
582void revert_creds(const struct cred *old)
583{
584	const struct cred *override = current->cred;
585
586	kdebug("revert_creds(%p{%d,%d})", old,
587	       atomic_read(&old->usage),
588	       read_cred_subscribers(old));
589
590	validate_creds(old);
591	validate_creds(override);
592	alter_cred_subscribers(old, 1);
593	rcu_assign_pointer(current->cred, old);
594	alter_cred_subscribers(override, -1);
595	put_cred(override);
596}
597EXPORT_SYMBOL(revert_creds);
598
599/**
600 * cred_fscmp - Compare two credentials with respect to filesystem access.
601 * @a: The first credential
602 * @b: The second credential
603 *
604 * cred_cmp() will return zero if both credentials have the same
605 * fsuid, fsgid, and supplementary groups.  That is, if they will both
606 * provide the same access to files based on mode/uid/gid.
607 * If the credentials are different, then either -1 or 1 will
608 * be returned depending on whether @a comes before or after @b
609 * respectively in an arbitrary, but stable, ordering of credentials.
610 *
611 * Return: -1, 0, or 1 depending on comparison
612 */
613int cred_fscmp(const struct cred *a, const struct cred *b)
614{
615	struct group_info *ga, *gb;
616	int g;
617
618	if (a == b)
619		return 0;
620	if (uid_lt(a->fsuid, b->fsuid))
621		return -1;
622	if (uid_gt(a->fsuid, b->fsuid))
623		return 1;
624
625	if (gid_lt(a->fsgid, b->fsgid))
626		return -1;
627	if (gid_gt(a->fsgid, b->fsgid))
628		return 1;
629
630	ga = a->group_info;
631	gb = b->group_info;
632	if (ga == gb)
633		return 0;
634	if (ga == NULL)
635		return -1;
636	if (gb == NULL)
637		return 1;
638	if (ga->ngroups < gb->ngroups)
639		return -1;
640	if (ga->ngroups > gb->ngroups)
641		return 1;
642
643	for (g = 0; g < ga->ngroups; g++) {
644		if (gid_lt(ga->gid[g], gb->gid[g]))
645			return -1;
646		if (gid_gt(ga->gid[g], gb->gid[g]))
647			return 1;
648	}
649	return 0;
650}
651EXPORT_SYMBOL(cred_fscmp);
652
653/*
654 * initialise the credentials stuff
655 */
656void __init cred_init(void)
657{
658	/* allocate a slab in which we can store credentials */
659	cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
660			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
661}
662
663/**
664 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
665 * @daemon: A userspace daemon to be used as a reference
666 *
667 * Prepare a set of credentials for a kernel service.  This can then be used to
668 * override a task's own credentials so that work can be done on behalf of that
669 * task that requires a different subjective context.
670 *
671 * @daemon is used to provide a base for the security record, but can be NULL.
672 * If @daemon is supplied, then the security data will be derived from that;
673 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
674 *
675 * The caller may change these controls afterwards if desired.
676 *
677 * Returns the new credentials or NULL if out of memory.
678 *
679 * Does not take, and does not return holding current->cred_replace_mutex.
680 */
681struct cred *prepare_kernel_cred(struct task_struct *daemon)
682{
683	const struct cred *old;
684	struct cred *new;
685
686	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
687	if (!new)
688		return NULL;
689
690	kdebug("prepare_kernel_cred() alloc %p", new);
691
692	if (daemon)
693		old = get_task_cred(daemon);
694	else
695		old = get_cred(&init_cred);
696
697	validate_creds(old);
698
699	*new = *old;
700	new->non_rcu = 0;
701	atomic_set(&new->usage, 1);
702	set_cred_subscribers(new, 0);
703	get_uid(new->user);
704	get_user_ns(new->user_ns);
705	get_group_info(new->group_info);
706
707#ifdef CONFIG_KEYS
708	new->session_keyring = NULL;
709	new->process_keyring = NULL;
710	new->thread_keyring = NULL;
711	new->request_key_auth = NULL;
712	new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
713#endif
714
715#ifdef CONFIG_SECURITY
716	new->security = NULL;
717#endif
718	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
719		goto error;
720
721	put_cred(old);
722	validate_creds(new);
723	return new;
724
725error:
726	put_cred(new);
727	put_cred(old);
728	return NULL;
729}
730EXPORT_SYMBOL(prepare_kernel_cred);
731
732/**
733 * set_security_override - Set the security ID in a set of credentials
734 * @new: The credentials to alter
735 * @secid: The LSM security ID to set
736 *
737 * Set the LSM security ID in a set of credentials so that the subjective
738 * security is overridden when an alternative set of credentials is used.
739 */
740int set_security_override(struct cred *new, u32 secid)
741{
742	return security_kernel_act_as(new, secid);
743}
744EXPORT_SYMBOL(set_security_override);
745
746/**
747 * set_security_override_from_ctx - Set the security ID in a set of credentials
748 * @new: The credentials to alter
749 * @secctx: The LSM security context to generate the security ID from.
750 *
751 * Set the LSM security ID in a set of credentials so that the subjective
752 * security is overridden when an alternative set of credentials is used.  The
753 * security ID is specified in string form as a security context to be
754 * interpreted by the LSM.
755 */
756int set_security_override_from_ctx(struct cred *new, const char *secctx)
757{
758	u32 secid;
759	int ret;
760
761	ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
762	if (ret < 0)
763		return ret;
764
765	return set_security_override(new, secid);
766}
767EXPORT_SYMBOL(set_security_override_from_ctx);
768
769/**
770 * set_create_files_as - Set the LSM file create context in a set of credentials
771 * @new: The credentials to alter
772 * @inode: The inode to take the context from
773 *
774 * Change the LSM file creation context in a set of credentials to be the same
775 * as the object context of the specified inode, so that the new inodes have
776 * the same MAC context as that inode.
777 */
778int set_create_files_as(struct cred *new, struct inode *inode)
779{
780	if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
781		return -EINVAL;
782	new->fsuid = inode->i_uid;
783	new->fsgid = inode->i_gid;
784	return security_kernel_create_files_as(new, inode);
785}
786EXPORT_SYMBOL(set_create_files_as);
787
788#ifdef CONFIG_DEBUG_CREDENTIALS
789
790bool creds_are_invalid(const struct cred *cred)
791{
792	if (cred->magic != CRED_MAGIC)
793		return true;
794	return false;
795}
796EXPORT_SYMBOL(creds_are_invalid);
797
798/*
799 * dump invalid credentials
800 */
801static void dump_invalid_creds(const struct cred *cred, const char *label,
802			       const struct task_struct *tsk)
803{
804	printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
805	       label, cred,
806	       cred == &init_cred ? "[init]" : "",
807	       cred == tsk->real_cred ? "[real]" : "",
808	       cred == tsk->cred ? "[eff]" : "");
809	printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
810	       cred->magic, cred->put_addr);
811	printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
812	       atomic_read(&cred->usage),
813	       read_cred_subscribers(cred));
814	printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
815		from_kuid_munged(&init_user_ns, cred->uid),
816		from_kuid_munged(&init_user_ns, cred->euid),
817		from_kuid_munged(&init_user_ns, cred->suid),
818		from_kuid_munged(&init_user_ns, cred->fsuid));
819	printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
820		from_kgid_munged(&init_user_ns, cred->gid),
821		from_kgid_munged(&init_user_ns, cred->egid),
822		from_kgid_munged(&init_user_ns, cred->sgid),
823		from_kgid_munged(&init_user_ns, cred->fsgid));
824#ifdef CONFIG_SECURITY
825	printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
826	if ((unsigned long) cred->security >= PAGE_SIZE &&
827	    (((unsigned long) cred->security & 0xffffff00) !=
828	     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
829		printk(KERN_ERR "CRED: ->security {%x, %x}\n",
830		       ((u32*)cred->security)[0],
831		       ((u32*)cred->security)[1]);
832#endif
833}
834
835/*
836 * report use of invalid credentials
837 */
838void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
839{
840	printk(KERN_ERR "CRED: Invalid credentials\n");
841	printk(KERN_ERR "CRED: At %s:%u\n", file, line);
842	dump_invalid_creds(cred, "Specified", current);
843	BUG();
844}
845EXPORT_SYMBOL(__invalid_creds);
846
847/*
848 * check the credentials on a process
849 */
850void __validate_process_creds(struct task_struct *tsk,
851			      const char *file, unsigned line)
852{
853	if (tsk->cred == tsk->real_cred) {
854		if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
855			     creds_are_invalid(tsk->cred)))
856			goto invalid_creds;
857	} else {
858		if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
859			     read_cred_subscribers(tsk->cred) < 1 ||
860			     creds_are_invalid(tsk->real_cred) ||
861			     creds_are_invalid(tsk->cred)))
862			goto invalid_creds;
863	}
864	return;
865
866invalid_creds:
867	printk(KERN_ERR "CRED: Invalid process credentials\n");
868	printk(KERN_ERR "CRED: At %s:%u\n", file, line);
869
870	dump_invalid_creds(tsk->real_cred, "Real", tsk);
871	if (tsk->cred != tsk->real_cred)
872		dump_invalid_creds(tsk->cred, "Effective", tsk);
873	else
874		printk(KERN_ERR "CRED: Effective creds == Real creds\n");
875	BUG();
876}
877EXPORT_SYMBOL(__validate_process_creds);
878
879/*
880 * check creds for do_exit()
881 */
882void validate_creds_for_do_exit(struct task_struct *tsk)
883{
884	kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
885	       tsk->real_cred, tsk->cred,
886	       atomic_read(&tsk->cred->usage),
887	       read_cred_subscribers(tsk->cred));
888
889	__validate_process_creds(tsk, __FILE__, __LINE__);
890}
891
892#endif /* CONFIG_DEBUG_CREDENTIALS */