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