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