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