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