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