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 */
 36static struct 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	.ucounts		= &init_ucounts,
 64};
 65
 66static inline void set_cred_subscribers(struct cred *cred, int n)
 67{
 68#ifdef CONFIG_DEBUG_CREDENTIALS
 69	atomic_set(&cred->subscribers, n);
 70#endif
 71}
 72
 73static inline int read_cred_subscribers(const struct cred *cred)
 74{
 75#ifdef CONFIG_DEBUG_CREDENTIALS
 76	return atomic_read(&cred->subscribers);
 77#else
 78	return 0;
 79#endif
 80}
 81
 82static inline void alter_cred_subscribers(const struct cred *_cred, int n)
 83{
 84#ifdef CONFIG_DEBUG_CREDENTIALS
 85	struct cred *cred = (struct cred *) _cred;
 86
 87	atomic_add(n, &cred->subscribers);
 88#endif
 89}
 90
 91/*
 92 * The RCU callback to actually dispose of a set of credentials
 93 */
 94static void put_cred_rcu(struct rcu_head *rcu)
 95{
 96	struct cred *cred = container_of(rcu, struct cred, rcu);
 97
 98	kdebug("put_cred_rcu(%p)", cred);
 99
100#ifdef CONFIG_DEBUG_CREDENTIALS
101	if (cred->magic != CRED_MAGIC_DEAD ||
102	    atomic_read(&cred->usage) != 0 ||
103	    read_cred_subscribers(cred) != 0)
104		panic("CRED: put_cred_rcu() sees %p with"
105		      " mag %x, put %p, usage %d, subscr %d\n",
106		      cred, cred->magic, cred->put_addr,
107		      atomic_read(&cred->usage),
108		      read_cred_subscribers(cred));
109#else
110	if (atomic_read(&cred->usage) != 0)
111		panic("CRED: put_cred_rcu() sees %p with usage %d\n",
112		      cred, atomic_read(&cred->usage));
113#endif
114
115	security_cred_free(cred);
116	key_put(cred->session_keyring);
117	key_put(cred->process_keyring);
118	key_put(cred->thread_keyring);
119	key_put(cred->request_key_auth);
120	if (cred->group_info)
121		put_group_info(cred->group_info);
122	free_uid(cred->user);
123	if (cred->ucounts)
124		put_ucounts(cred->ucounts);
125	put_user_ns(cred->user_ns);
126	kmem_cache_free(cred_jar, cred);
127}
128
129/**
130 * __put_cred - Destroy a set of credentials
131 * @cred: The record to release
132 *
133 * Destroy a set of credentials on which no references remain.
134 */
135void __put_cred(struct cred *cred)
136{
137	kdebug("__put_cred(%p{%d,%d})", cred,
138	       atomic_read(&cred->usage),
139	       read_cred_subscribers(cred));
140
141	BUG_ON(atomic_read(&cred->usage) != 0);
142#ifdef CONFIG_DEBUG_CREDENTIALS
143	BUG_ON(read_cred_subscribers(cred) != 0);
144	cred->magic = CRED_MAGIC_DEAD;
145	cred->put_addr = __builtin_return_address(0);
146#endif
147	BUG_ON(cred == current->cred);
148	BUG_ON(cred == current->real_cred);
149
150	if (cred->non_rcu)
151		put_cred_rcu(&cred->rcu);
152	else
153		call_rcu(&cred->rcu, put_cred_rcu);
154}
155EXPORT_SYMBOL(__put_cred);
156
157/*
158 * Clean up a task's credentials when it exits
159 */
160void exit_creds(struct task_struct *tsk)
161{
162	struct cred *cred;
163
164	kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
165	       atomic_read(&tsk->cred->usage),
166	       read_cred_subscribers(tsk->cred));
167
168	cred = (struct cred *) tsk->real_cred;
169	tsk->real_cred = NULL;
170	validate_creds(cred);
171	alter_cred_subscribers(cred, -1);
172	put_cred(cred);
173
174	cred = (struct cred *) tsk->cred;
175	tsk->cred = NULL;
176	validate_creds(cred);
177	alter_cred_subscribers(cred, -1);
178	put_cred(cred);
179
180#ifdef CONFIG_KEYS_REQUEST_CACHE
181	key_put(tsk->cached_requested_key);
182	tsk->cached_requested_key = NULL;
183#endif
184}
185
186/**
187 * get_task_cred - Get another task's objective credentials
188 * @task: The task to query
189 *
190 * Get the objective credentials of a task, pinning them so that they can't go
191 * away.  Accessing a task's credentials directly is not permitted.
192 *
193 * The caller must also make sure task doesn't get deleted, either by holding a
194 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
195 */
196const struct cred *get_task_cred(struct task_struct *task)
197{
198	const struct cred *cred;
199
200	rcu_read_lock();
201
202	do {
203		cred = __task_cred((task));
204		BUG_ON(!cred);
205	} while (!get_cred_rcu(cred));
206
207	rcu_read_unlock();
208	return cred;
209}
210EXPORT_SYMBOL(get_task_cred);
211
212/*
213 * Allocate blank credentials, such that the credentials can be filled in at a
214 * later date without risk of ENOMEM.
215 */
216struct cred *cred_alloc_blank(void)
217{
218	struct cred *new;
219
220	new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
221	if (!new)
222		return NULL;
223
224	atomic_set(&new->usage, 1);
225#ifdef CONFIG_DEBUG_CREDENTIALS
226	new->magic = CRED_MAGIC;
227#endif
 
228	if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
229		goto error;
230
231	return new;
232
233error:
234	abort_creds(new);
235	return NULL;
236}
237
238/**
239 * prepare_creds - Prepare a new set of credentials for modification
240 *
241 * Prepare a new set of task credentials for modification.  A task's creds
242 * shouldn't generally be modified directly, therefore this function is used to
243 * prepare a new copy, which the caller then modifies and then commits by
244 * calling commit_creds().
245 *
246 * Preparation involves making a copy of the objective creds for modification.
247 *
248 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
249 *
250 * Call commit_creds() or abort_creds() to clean up.
251 */
252struct cred *prepare_creds(void)
253{
254	struct task_struct *task = current;
255	const struct cred *old;
256	struct cred *new;
257
258	validate_process_creds();
259
260	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
261	if (!new)
262		return NULL;
263
264	kdebug("prepare_creds() alloc %p", new);
265
266	old = task->cred;
267	memcpy(new, old, sizeof(struct cred));
268
269	new->non_rcu = 0;
270	atomic_set(&new->usage, 1);
271	set_cred_subscribers(new, 0);
272	get_group_info(new->group_info);
273	get_uid(new->user);
274	get_user_ns(new->user_ns);
275
276#ifdef CONFIG_KEYS
277	key_get(new->session_keyring);
278	key_get(new->process_keyring);
279	key_get(new->thread_keyring);
280	key_get(new->request_key_auth);
281#endif
282
283#ifdef CONFIG_SECURITY
284	new->security = NULL;
285#endif
286
287	new->ucounts = get_ucounts(new->ucounts);
288	if (!new->ucounts)
289		goto error;
290
291	if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
292		goto error;
293
294	validate_creds(new);
295	return new;
296
297error:
298	abort_creds(new);
299	return NULL;
300}
301EXPORT_SYMBOL(prepare_creds);
302
303/*
304 * Prepare credentials for current to perform an execve()
305 * - The caller must hold ->cred_guard_mutex
306 */
307struct cred *prepare_exec_creds(void)
308{
309	struct cred *new;
310
311	new = prepare_creds();
312	if (!new)
313		return new;
314
315#ifdef CONFIG_KEYS
316	/* newly exec'd tasks don't get a thread keyring */
317	key_put(new->thread_keyring);
318	new->thread_keyring = NULL;
319
320	/* inherit the session keyring; new process keyring */
321	key_put(new->process_keyring);
322	new->process_keyring = NULL;
323#endif
324
325	new->suid = new->fsuid = new->euid;
326	new->sgid = new->fsgid = new->egid;
327
328	return new;
329}
330
331/*
332 * Copy credentials for the new process created by fork()
333 *
334 * We share if we can, but under some circumstances we have to generate a new
335 * set.
336 *
337 * The new process gets the current process's subjective credentials as its
338 * objective and subjective credentials
339 */
340int copy_creds(struct task_struct *p, unsigned long clone_flags)
341{
342	struct cred *new;
343	int ret;
344
345#ifdef CONFIG_KEYS_REQUEST_CACHE
346	p->cached_requested_key = NULL;
347#endif
348
349	if (
350#ifdef CONFIG_KEYS
351		!p->cred->thread_keyring &&
352#endif
353		clone_flags & CLONE_THREAD
354	    ) {
355		p->real_cred = get_cred(p->cred);
356		get_cred(p->cred);
357		alter_cred_subscribers(p->cred, 2);
358		kdebug("share_creds(%p{%d,%d})",
359		       p->cred, atomic_read(&p->cred->usage),
360		       read_cred_subscribers(p->cred));
361		inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
362		return 0;
363	}
364
365	new = prepare_creds();
366	if (!new)
367		return -ENOMEM;
368
369	if (clone_flags & CLONE_NEWUSER) {
370		ret = create_user_ns(new);
371		if (ret < 0)
372			goto error_put;
373		ret = set_cred_ucounts(new);
374		if (ret < 0)
375			goto error_put;
376	}
377
378#ifdef CONFIG_KEYS
379	/* new threads get their own thread keyrings if their parent already
380	 * had one */
381	if (new->thread_keyring) {
382		key_put(new->thread_keyring);
383		new->thread_keyring = NULL;
384		if (clone_flags & CLONE_THREAD)
385			install_thread_keyring_to_cred(new);
386	}
387
388	/* The process keyring is only shared between the threads in a process;
389	 * anything outside of those threads doesn't inherit.
390	 */
391	if (!(clone_flags & CLONE_THREAD)) {
392		key_put(new->process_keyring);
393		new->process_keyring = NULL;
394	}
395#endif
396
 
397	p->cred = p->real_cred = get_cred(new);
398	inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
399	alter_cred_subscribers(new, 2);
400	validate_creds(new);
401	return 0;
402
403error_put:
404	put_cred(new);
405	return ret;
406}
407
408static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
409{
410	const struct user_namespace *set_ns = set->user_ns;
411	const struct user_namespace *subset_ns = subset->user_ns;
412
413	/* If the two credentials are in the same user namespace see if
414	 * the capabilities of subset are a subset of set.
415	 */
416	if (set_ns == subset_ns)
417		return cap_issubset(subset->cap_permitted, set->cap_permitted);
418
419	/* The credentials are in a different user namespaces
420	 * therefore one is a subset of the other only if a set is an
421	 * ancestor of subset and set->euid is owner of subset or one
422	 * of subsets ancestors.
423	 */
424	for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
425		if ((set_ns == subset_ns->parent)  &&
426		    uid_eq(subset_ns->owner, set->euid))
427			return true;
428	}
429
430	return false;
431}
432
433/**
434 * commit_creds - Install new credentials upon the current task
435 * @new: The credentials to be assigned
436 *
437 * Install a new set of credentials to the current task, using RCU to replace
438 * the old set.  Both the objective and the subjective credentials pointers are
439 * updated.  This function may not be called if the subjective credentials are
440 * in an overridden state.
441 *
442 * This function eats the caller's reference to the new credentials.
443 *
444 * Always returns 0 thus allowing this function to be tail-called at the end
445 * of, say, sys_setgid().
446 */
447int commit_creds(struct cred *new)
448{
449	struct task_struct *task = current;
450	const struct cred *old = task->real_cred;
451
452	kdebug("commit_creds(%p{%d,%d})", new,
453	       atomic_read(&new->usage),
454	       read_cred_subscribers(new));
455
456	BUG_ON(task->cred != old);
457#ifdef CONFIG_DEBUG_CREDENTIALS
458	BUG_ON(read_cred_subscribers(old) < 2);
459	validate_creds(old);
460	validate_creds(new);
461#endif
462	BUG_ON(atomic_read(&new->usage) < 1);
463
464	get_cred(new); /* we will require a ref for the subj creds too */
465
466	/* dumpability changes */
467	if (!uid_eq(old->euid, new->euid) ||
468	    !gid_eq(old->egid, new->egid) ||
469	    !uid_eq(old->fsuid, new->fsuid) ||
470	    !gid_eq(old->fsgid, new->fsgid) ||
471	    !cred_cap_issubset(old, new)) {
472		if (task->mm)
473			set_dumpable(task->mm, suid_dumpable);
474		task->pdeath_signal = 0;
475		/*
476		 * If a task drops privileges and becomes nondumpable,
477		 * the dumpability change must become visible before
478		 * the credential change; otherwise, a __ptrace_may_access()
479		 * racing with this change may be able to attach to a task it
480		 * shouldn't be able to attach to (as if the task had dropped
481		 * privileges without becoming nondumpable).
482		 * Pairs with a read barrier in __ptrace_may_access().
483		 */
484		smp_wmb();
485	}
486
487	/* alter the thread keyring */
488	if (!uid_eq(new->fsuid, old->fsuid))
489		key_fsuid_changed(new);
490	if (!gid_eq(new->fsgid, old->fsgid))
491		key_fsgid_changed(new);
492
493	/* do it
494	 * RLIMIT_NPROC limits on user->processes have already been checked
495	 * in set_user().
496	 */
497	alter_cred_subscribers(new, 2);
498	if (new->user != old->user || new->user_ns != old->user_ns)
499		inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1);
500	rcu_assign_pointer(task->real_cred, new);
501	rcu_assign_pointer(task->cred, new);
502	if (new->user != old->user || new->user_ns != old->user_ns)
503		dec_rlimit_ucounts(old->ucounts, UCOUNT_RLIMIT_NPROC, 1);
504	alter_cred_subscribers(old, -2);
505
506	/* send notifications */
507	if (!uid_eq(new->uid,   old->uid)  ||
508	    !uid_eq(new->euid,  old->euid) ||
509	    !uid_eq(new->suid,  old->suid) ||
510	    !uid_eq(new->fsuid, old->fsuid))
511		proc_id_connector(task, PROC_EVENT_UID);
512
513	if (!gid_eq(new->gid,   old->gid)  ||
514	    !gid_eq(new->egid,  old->egid) ||
515	    !gid_eq(new->sgid,  old->sgid) ||
516	    !gid_eq(new->fsgid, old->fsgid))
517		proc_id_connector(task, PROC_EVENT_GID);
518
519	/* release the old obj and subj refs both */
520	put_cred(old);
521	put_cred(old);
522	return 0;
523}
524EXPORT_SYMBOL(commit_creds);
525
526/**
527 * abort_creds - Discard a set of credentials and unlock the current task
528 * @new: The credentials that were going to be applied
529 *
530 * Discard a set of credentials that were under construction and unlock the
531 * current task.
532 */
533void abort_creds(struct cred *new)
534{
535	kdebug("abort_creds(%p{%d,%d})", new,
536	       atomic_read(&new->usage),
537	       read_cred_subscribers(new));
538
539#ifdef CONFIG_DEBUG_CREDENTIALS
540	BUG_ON(read_cred_subscribers(new) != 0);
541#endif
542	BUG_ON(atomic_read(&new->usage) < 1);
543	put_cred(new);
544}
545EXPORT_SYMBOL(abort_creds);
546
547/**
548 * override_creds - Override the current process's subjective credentials
549 * @new: The credentials to be assigned
550 *
551 * Install a set of temporary override subjective credentials on the current
552 * process, returning the old set for later reversion.
553 */
554const struct cred *override_creds(const struct cred *new)
555{
556	const struct cred *old = current->cred;
557
558	kdebug("override_creds(%p{%d,%d})", new,
559	       atomic_read(&new->usage),
560	       read_cred_subscribers(new));
561
562	validate_creds(old);
563	validate_creds(new);
564
565	/*
566	 * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
567	 *
568	 * That means that we do not clear the 'non_rcu' flag, since
569	 * we are only installing the cred into the thread-synchronous
570	 * '->cred' pointer, not the '->real_cred' pointer that is
571	 * visible to other threads under RCU.
572	 *
573	 * Also note that we did validate_creds() manually, not depending
574	 * on the validation in 'get_cred()'.
575	 */
576	get_new_cred((struct cred *)new);
577	alter_cred_subscribers(new, 1);
578	rcu_assign_pointer(current->cred, new);
579	alter_cred_subscribers(old, -1);
580
581	kdebug("override_creds() = %p{%d,%d}", old,
582	       atomic_read(&old->usage),
583	       read_cred_subscribers(old));
584	return old;
585}
586EXPORT_SYMBOL(override_creds);
587
588/**
589 * revert_creds - Revert a temporary subjective credentials override
590 * @old: The credentials to be restored
591 *
592 * Revert a temporary set of override subjective credentials to an old set,
593 * discarding the override set.
594 */
595void revert_creds(const struct cred *old)
596{
597	const struct cred *override = current->cred;
598
599	kdebug("revert_creds(%p{%d,%d})", old,
600	       atomic_read(&old->usage),
601	       read_cred_subscribers(old));
602
603	validate_creds(old);
604	validate_creds(override);
605	alter_cred_subscribers(old, 1);
606	rcu_assign_pointer(current->cred, old);
607	alter_cred_subscribers(override, -1);
608	put_cred(override);
609}
610EXPORT_SYMBOL(revert_creds);
611
612/**
613 * cred_fscmp - Compare two credentials with respect to filesystem access.
614 * @a: The first credential
615 * @b: The second credential
616 *
617 * cred_cmp() will return zero if both credentials have the same
618 * fsuid, fsgid, and supplementary groups.  That is, if they will both
619 * provide the same access to files based on mode/uid/gid.
620 * If the credentials are different, then either -1 or 1 will
621 * be returned depending on whether @a comes before or after @b
622 * respectively in an arbitrary, but stable, ordering of credentials.
623 *
624 * Return: -1, 0, or 1 depending on comparison
625 */
626int cred_fscmp(const struct cred *a, const struct cred *b)
627{
628	struct group_info *ga, *gb;
629	int g;
630
631	if (a == b)
632		return 0;
633	if (uid_lt(a->fsuid, b->fsuid))
634		return -1;
635	if (uid_gt(a->fsuid, b->fsuid))
636		return 1;
637
638	if (gid_lt(a->fsgid, b->fsgid))
639		return -1;
640	if (gid_gt(a->fsgid, b->fsgid))
641		return 1;
642
643	ga = a->group_info;
644	gb = b->group_info;
645	if (ga == gb)
646		return 0;
647	if (ga == NULL)
648		return -1;
649	if (gb == NULL)
650		return 1;
651	if (ga->ngroups < gb->ngroups)
652		return -1;
653	if (ga->ngroups > gb->ngroups)
654		return 1;
655
656	for (g = 0; g < ga->ngroups; g++) {
657		if (gid_lt(ga->gid[g], gb->gid[g]))
658			return -1;
659		if (gid_gt(ga->gid[g], gb->gid[g]))
660			return 1;
661	}
662	return 0;
663}
664EXPORT_SYMBOL(cred_fscmp);
665
666int set_cred_ucounts(struct cred *new)
667{
668	struct ucounts *new_ucounts, *old_ucounts = new->ucounts;
669
670	/*
671	 * This optimization is needed because alloc_ucounts() uses locks
672	 * for table lookups.
673	 */
674	if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->uid))
675		return 0;
676
677	if (!(new_ucounts = alloc_ucounts(new->user_ns, new->uid)))
678		return -EAGAIN;
679
680	new->ucounts = new_ucounts;
681	put_ucounts(old_ucounts);
682
683	return 0;
684}
685
686/*
687 * initialise the credentials stuff
688 */
689void __init cred_init(void)
690{
691	/* allocate a slab in which we can store credentials */
692	cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
693			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
694}
695
696/**
697 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
698 * @daemon: A userspace daemon to be used as a reference
699 *
700 * Prepare a set of credentials for a kernel service.  This can then be used to
701 * override a task's own credentials so that work can be done on behalf of that
702 * task that requires a different subjective context.
703 *
704 * @daemon is used to provide a base cred, with the security data derived from
705 * that; if this is "&init_task", they'll be set to 0, no groups, full
706 * capabilities, and no keys.
707 *
708 * The caller may change these controls afterwards if desired.
709 *
710 * Returns the new credentials or NULL if out of memory.
711 */
712struct cred *prepare_kernel_cred(struct task_struct *daemon)
713{
714	const struct cred *old;
715	struct cred *new;
716
717	if (WARN_ON_ONCE(!daemon))
718		return NULL;
719
720	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
721	if (!new)
722		return NULL;
723
724	kdebug("prepare_kernel_cred() alloc %p", new);
725
726	old = get_task_cred(daemon);
 
 
 
 
727	validate_creds(old);
728
729	*new = *old;
730	new->non_rcu = 0;
731	atomic_set(&new->usage, 1);
732	set_cred_subscribers(new, 0);
733	get_uid(new->user);
734	get_user_ns(new->user_ns);
735	get_group_info(new->group_info);
736
737#ifdef CONFIG_KEYS
738	new->session_keyring = NULL;
739	new->process_keyring = NULL;
740	new->thread_keyring = NULL;
741	new->request_key_auth = NULL;
742	new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
743#endif
744
745#ifdef CONFIG_SECURITY
746	new->security = NULL;
747#endif
748	new->ucounts = get_ucounts(new->ucounts);
749	if (!new->ucounts)
750		goto error;
751
752	if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
753		goto error;
754
755	put_cred(old);
756	validate_creds(new);
757	return new;
758
759error:
760	put_cred(new);
761	put_cred(old);
762	return NULL;
763}
764EXPORT_SYMBOL(prepare_kernel_cred);
765
766/**
767 * set_security_override - Set the security ID in a set of credentials
768 * @new: The credentials to alter
769 * @secid: The LSM security ID to set
770 *
771 * Set the LSM security ID in a set of credentials so that the subjective
772 * security is overridden when an alternative set of credentials is used.
773 */
774int set_security_override(struct cred *new, u32 secid)
775{
776	return security_kernel_act_as(new, secid);
777}
778EXPORT_SYMBOL(set_security_override);
779
780/**
781 * set_security_override_from_ctx - Set the security ID in a set of credentials
782 * @new: The credentials to alter
783 * @secctx: The LSM security context to generate the security ID from.
784 *
785 * Set the LSM security ID in a set of credentials so that the subjective
786 * security is overridden when an alternative set of credentials is used.  The
787 * security ID is specified in string form as a security context to be
788 * interpreted by the LSM.
789 */
790int set_security_override_from_ctx(struct cred *new, const char *secctx)
791{
792	u32 secid;
793	int ret;
794
795	ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
796	if (ret < 0)
797		return ret;
798
799	return set_security_override(new, secid);
800}
801EXPORT_SYMBOL(set_security_override_from_ctx);
802
803/**
804 * set_create_files_as - Set the LSM file create context in a set of credentials
805 * @new: The credentials to alter
806 * @inode: The inode to take the context from
807 *
808 * Change the LSM file creation context in a set of credentials to be the same
809 * as the object context of the specified inode, so that the new inodes have
810 * the same MAC context as that inode.
811 */
812int set_create_files_as(struct cred *new, struct inode *inode)
813{
814	if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
815		return -EINVAL;
816	new->fsuid = inode->i_uid;
817	new->fsgid = inode->i_gid;
818	return security_kernel_create_files_as(new, inode);
819}
820EXPORT_SYMBOL(set_create_files_as);
821
822#ifdef CONFIG_DEBUG_CREDENTIALS
823
824bool creds_are_invalid(const struct cred *cred)
825{
826	if (cred->magic != CRED_MAGIC)
827		return true;
828	return false;
829}
830EXPORT_SYMBOL(creds_are_invalid);
831
832/*
833 * dump invalid credentials
834 */
835static void dump_invalid_creds(const struct cred *cred, const char *label,
836			       const struct task_struct *tsk)
837{
838	printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
839	       label, cred,
840	       cred == &init_cred ? "[init]" : "",
841	       cred == tsk->real_cred ? "[real]" : "",
842	       cred == tsk->cred ? "[eff]" : "");
843	printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
844	       cred->magic, cred->put_addr);
845	printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
846	       atomic_read(&cred->usage),
847	       read_cred_subscribers(cred));
848	printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
849		from_kuid_munged(&init_user_ns, cred->uid),
850		from_kuid_munged(&init_user_ns, cred->euid),
851		from_kuid_munged(&init_user_ns, cred->suid),
852		from_kuid_munged(&init_user_ns, cred->fsuid));
853	printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
854		from_kgid_munged(&init_user_ns, cred->gid),
855		from_kgid_munged(&init_user_ns, cred->egid),
856		from_kgid_munged(&init_user_ns, cred->sgid),
857		from_kgid_munged(&init_user_ns, cred->fsgid));
858#ifdef CONFIG_SECURITY
859	printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
860	if ((unsigned long) cred->security >= PAGE_SIZE &&
861	    (((unsigned long) cred->security & 0xffffff00) !=
862	     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
863		printk(KERN_ERR "CRED: ->security {%x, %x}\n",
864		       ((u32*)cred->security)[0],
865		       ((u32*)cred->security)[1]);
866#endif
867}
868
869/*
870 * report use of invalid credentials
871 */
872void __noreturn __invalid_creds(const struct cred *cred, const char *file, unsigned line)
873{
874	printk(KERN_ERR "CRED: Invalid credentials\n");
875	printk(KERN_ERR "CRED: At %s:%u\n", file, line);
876	dump_invalid_creds(cred, "Specified", current);
877	BUG();
878}
879EXPORT_SYMBOL(__invalid_creds);
880
881/*
882 * check the credentials on a process
883 */
884void __validate_process_creds(struct task_struct *tsk,
885			      const char *file, unsigned line)
886{
887	if (tsk->cred == tsk->real_cred) {
888		if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
889			     creds_are_invalid(tsk->cred)))
890			goto invalid_creds;
891	} else {
892		if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
893			     read_cred_subscribers(tsk->cred) < 1 ||
894			     creds_are_invalid(tsk->real_cred) ||
895			     creds_are_invalid(tsk->cred)))
896			goto invalid_creds;
897	}
898	return;
899
900invalid_creds:
901	printk(KERN_ERR "CRED: Invalid process credentials\n");
902	printk(KERN_ERR "CRED: At %s:%u\n", file, line);
903
904	dump_invalid_creds(tsk->real_cred, "Real", tsk);
905	if (tsk->cred != tsk->real_cred)
906		dump_invalid_creds(tsk->cred, "Effective", tsk);
907	else
908		printk(KERN_ERR "CRED: Effective creds == Real creds\n");
909	BUG();
910}
911EXPORT_SYMBOL(__validate_process_creds);
912
913/*
914 * check creds for do_exit()
915 */
916void validate_creds_for_do_exit(struct task_struct *tsk)
917{
918	kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
919	       tsk->real_cred, tsk->cred,
920	       atomic_read(&tsk->cred->usage),
921	       read_cred_subscribers(tsk->cred));
922
923	__validate_process_creds(tsk, __FILE__, __LINE__);
924}
925
926#endif /* CONFIG_DEBUG_CREDENTIALS */