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