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