umh: creds: convert call_usermodehelper_keys() to use subprocess_info->init()
[linux-2.6.git] / kernel / cred.c
1 /* Task credentials management - see Documentation/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/module.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/cn_proc.h>
20
21 #if 0
22 #define kdebug(FMT, ...) \
23         printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
24 #else
25 static inline __attribute__((format(printf, 1, 2)))
26 void no_printk(const char *fmt, ...)
27 {
28 }
29 #define kdebug(FMT, ...) \
30         no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
31 #endif
32
33 static struct kmem_cache *cred_jar;
34
35 /*
36  * The common credentials for the initial task's thread group
37  */
38 #ifdef CONFIG_KEYS
39 static struct thread_group_cred init_tgcred = {
40         .usage  = ATOMIC_INIT(2),
41         .tgid   = 0,
42         .lock   = SPIN_LOCK_UNLOCKED,
43 };
44 #endif
45
46 /*
47  * The initial credentials for the initial task
48  */
49 struct cred init_cred = {
50         .usage                  = ATOMIC_INIT(4),
51 #ifdef CONFIG_DEBUG_CREDENTIALS
52         .subscribers            = ATOMIC_INIT(2),
53         .magic                  = CRED_MAGIC,
54 #endif
55         .securebits             = SECUREBITS_DEFAULT,
56         .cap_inheritable        = CAP_INIT_INH_SET,
57         .cap_permitted          = CAP_FULL_SET,
58         .cap_effective          = CAP_INIT_EFF_SET,
59         .cap_bset               = CAP_INIT_BSET,
60         .user                   = INIT_USER,
61         .group_info             = &init_groups,
62 #ifdef CONFIG_KEYS
63         .tgcred                 = &init_tgcred,
64 #endif
65 };
66
67 static inline void set_cred_subscribers(struct cred *cred, int n)
68 {
69 #ifdef CONFIG_DEBUG_CREDENTIALS
70         atomic_set(&cred->subscribers, n);
71 #endif
72 }
73
74 static inline int read_cred_subscribers(const struct cred *cred)
75 {
76 #ifdef CONFIG_DEBUG_CREDENTIALS
77         return atomic_read(&cred->subscribers);
78 #else
79         return 0;
80 #endif
81 }
82
83 static inline void alter_cred_subscribers(const struct cred *_cred, int n)
84 {
85 #ifdef CONFIG_DEBUG_CREDENTIALS
86         struct cred *cred = (struct cred *) _cred;
87
88         atomic_add(n, &cred->subscribers);
89 #endif
90 }
91
92 /*
93  * Dispose of the shared task group credentials
94  */
95 #ifdef CONFIG_KEYS
96 static void release_tgcred_rcu(struct rcu_head *rcu)
97 {
98         struct thread_group_cred *tgcred =
99                 container_of(rcu, struct thread_group_cred, rcu);
100
101         BUG_ON(atomic_read(&tgcred->usage) != 0);
102
103         key_put(tgcred->session_keyring);
104         key_put(tgcred->process_keyring);
105         kfree(tgcred);
106 }
107 #endif
108
109 /*
110  * Release a set of thread group credentials.
111  */
112 static void release_tgcred(struct cred *cred)
113 {
114 #ifdef CONFIG_KEYS
115         struct thread_group_cred *tgcred = cred->tgcred;
116
117         if (atomic_dec_and_test(&tgcred->usage))
118                 call_rcu(&tgcred->rcu, release_tgcred_rcu);
119 #endif
120 }
121
122 /*
123  * The RCU callback to actually dispose of a set of credentials
124  */
125 static void put_cred_rcu(struct rcu_head *rcu)
126 {
127         struct cred *cred = container_of(rcu, struct cred, rcu);
128
129         kdebug("put_cred_rcu(%p)", cred);
130
131 #ifdef CONFIG_DEBUG_CREDENTIALS
132         if (cred->magic != CRED_MAGIC_DEAD ||
133             atomic_read(&cred->usage) != 0 ||
134             read_cred_subscribers(cred) != 0)
135                 panic("CRED: put_cred_rcu() sees %p with"
136                       " mag %x, put %p, usage %d, subscr %d\n",
137                       cred, cred->magic, cred->put_addr,
138                       atomic_read(&cred->usage),
139                       read_cred_subscribers(cred));
140 #else
141         if (atomic_read(&cred->usage) != 0)
142                 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
143                       cred, atomic_read(&cred->usage));
144 #endif
145
146         security_cred_free(cred);
147         key_put(cred->thread_keyring);
148         key_put(cred->request_key_auth);
149         release_tgcred(cred);
150         if (cred->group_info)
151                 put_group_info(cred->group_info);
152         free_uid(cred->user);
153         kmem_cache_free(cred_jar, cred);
154 }
155
156 /**
157  * __put_cred - Destroy a set of credentials
158  * @cred: The record to release
159  *
160  * Destroy a set of credentials on which no references remain.
161  */
162 void __put_cred(struct cred *cred)
163 {
164         kdebug("__put_cred(%p{%d,%d})", cred,
165                atomic_read(&cred->usage),
166                read_cred_subscribers(cred));
167
168         BUG_ON(atomic_read(&cred->usage) != 0);
169 #ifdef CONFIG_DEBUG_CREDENTIALS
170         BUG_ON(read_cred_subscribers(cred) != 0);
171         cred->magic = CRED_MAGIC_DEAD;
172         cred->put_addr = __builtin_return_address(0);
173 #endif
174         BUG_ON(cred == current->cred);
175         BUG_ON(cred == current->real_cred);
176
177         call_rcu(&cred->rcu, put_cred_rcu);
178 }
179 EXPORT_SYMBOL(__put_cred);
180
181 /*
182  * Clean up a task's credentials when it exits
183  */
184 void exit_creds(struct task_struct *tsk)
185 {
186         struct cred *cred;
187
188         kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
189                atomic_read(&tsk->cred->usage),
190                read_cred_subscribers(tsk->cred));
191
192         cred = (struct cred *) tsk->real_cred;
193         tsk->real_cred = NULL;
194         validate_creds(cred);
195         alter_cred_subscribers(cred, -1);
196         put_cred(cred);
197
198         cred = (struct cred *) tsk->cred;
199         tsk->cred = NULL;
200         validate_creds(cred);
201         alter_cred_subscribers(cred, -1);
202         put_cred(cred);
203
204         cred = (struct cred *) tsk->replacement_session_keyring;
205         if (cred) {
206                 tsk->replacement_session_keyring = NULL;
207                 validate_creds(cred);
208                 put_cred(cred);
209         }
210 }
211
212 /*
213  * Allocate blank credentials, such that the credentials can be filled in at a
214  * later date without risk of ENOMEM.
215  */
216 struct cred *cred_alloc_blank(void)
217 {
218         struct cred *new;
219
220         new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
221         if (!new)
222                 return NULL;
223
224 #ifdef CONFIG_KEYS
225         new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
226         if (!new->tgcred) {
227                 kmem_cache_free(cred_jar, new);
228                 return NULL;
229         }
230         atomic_set(&new->tgcred->usage, 1);
231 #endif
232
233         atomic_set(&new->usage, 1);
234
235         if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
236                 goto error;
237
238 #ifdef CONFIG_DEBUG_CREDENTIALS
239         new->magic = CRED_MAGIC;
240 #endif
241         return new;
242
243 error:
244         abort_creds(new);
245         return NULL;
246 }
247
248 /**
249  * prepare_creds - Prepare a new set of credentials for modification
250  *
251  * Prepare a new set of task credentials for modification.  A task's creds
252  * shouldn't generally be modified directly, therefore this function is used to
253  * prepare a new copy, which the caller then modifies and then commits by
254  * calling commit_creds().
255  *
256  * Preparation involves making a copy of the objective creds for modification.
257  *
258  * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
259  *
260  * Call commit_creds() or abort_creds() to clean up.
261  */
262 struct cred *prepare_creds(void)
263 {
264         struct task_struct *task = current;
265         const struct cred *old;
266         struct cred *new;
267
268         validate_process_creds();
269
270         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
271         if (!new)
272                 return NULL;
273
274         kdebug("prepare_creds() alloc %p", new);
275
276         old = task->cred;
277         memcpy(new, old, sizeof(struct cred));
278
279         atomic_set(&new->usage, 1);
280         set_cred_subscribers(new, 0);
281         get_group_info(new->group_info);
282         get_uid(new->user);
283
284 #ifdef CONFIG_KEYS
285         key_get(new->thread_keyring);
286         key_get(new->request_key_auth);
287         atomic_inc(&new->tgcred->usage);
288 #endif
289
290 #ifdef CONFIG_SECURITY
291         new->security = NULL;
292 #endif
293
294         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
295                 goto error;
296         validate_creds(new);
297         return new;
298
299 error:
300         abort_creds(new);
301         return NULL;
302 }
303 EXPORT_SYMBOL(prepare_creds);
304
305 /*
306  * Prepare credentials for current to perform an execve()
307  * - The caller must hold current->cred_guard_mutex
308  */
309 struct cred *prepare_exec_creds(void)
310 {
311         struct thread_group_cred *tgcred = NULL;
312         struct cred *new;
313
314 #ifdef CONFIG_KEYS
315         tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
316         if (!tgcred)
317                 return NULL;
318 #endif
319
320         new = prepare_creds();
321         if (!new) {
322                 kfree(tgcred);
323                 return new;
324         }
325
326 #ifdef CONFIG_KEYS
327         /* newly exec'd tasks don't get a thread keyring */
328         key_put(new->thread_keyring);
329         new->thread_keyring = NULL;
330
331         /* create a new per-thread-group creds for all this set of threads to
332          * share */
333         memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
334
335         atomic_set(&tgcred->usage, 1);
336         spin_lock_init(&tgcred->lock);
337
338         /* inherit the session keyring; new process keyring */
339         key_get(tgcred->session_keyring);
340         tgcred->process_keyring = NULL;
341
342         release_tgcred(new);
343         new->tgcred = tgcred;
344 #endif
345
346         return new;
347 }
348
349 /*
350  * prepare new credentials for the usermode helper dispatcher
351  */
352 struct cred *prepare_usermodehelper_creds(void)
353 {
354 #ifdef CONFIG_KEYS
355         struct thread_group_cred *tgcred = NULL;
356 #endif
357         struct cred *new;
358
359 #ifdef CONFIG_KEYS
360         tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
361         if (!tgcred)
362                 return NULL;
363 #endif
364
365         new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
366         if (!new)
367                 goto free_tgcred;
368
369         kdebug("prepare_usermodehelper_creds() alloc %p", new);
370
371         memcpy(new, &init_cred, sizeof(struct cred));
372
373         atomic_set(&new->usage, 1);
374         set_cred_subscribers(new, 0);
375         get_group_info(new->group_info);
376         get_uid(new->user);
377
378 #ifdef CONFIG_KEYS
379         new->thread_keyring = NULL;
380         new->request_key_auth = NULL;
381         new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
382
383         atomic_set(&tgcred->usage, 1);
384         spin_lock_init(&tgcred->lock);
385         new->tgcred = tgcred;
386 #endif
387
388 #ifdef CONFIG_SECURITY
389         new->security = NULL;
390 #endif
391         if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
392                 goto error;
393         validate_creds(new);
394
395         BUG_ON(atomic_read(&new->usage) != 1);
396         return new;
397
398 error:
399         put_cred(new);
400         return NULL;
401
402 free_tgcred:
403 #ifdef CONFIG_KEYS
404         kfree(tgcred);
405 #endif
406         return NULL;
407 }
408
409 /*
410  * Copy credentials for the new process created by fork()
411  *
412  * We share if we can, but under some circumstances we have to generate a new
413  * set.
414  *
415  * The new process gets the current process's subjective credentials as its
416  * objective and subjective credentials
417  */
418 int copy_creds(struct task_struct *p, unsigned long clone_flags)
419 {
420 #ifdef CONFIG_KEYS
421         struct thread_group_cred *tgcred;
422 #endif
423         struct cred *new;
424         int ret;
425
426         mutex_init(&p->cred_guard_mutex);
427
428         if (
429 #ifdef CONFIG_KEYS
430                 !p->cred->thread_keyring &&
431 #endif
432                 clone_flags & CLONE_THREAD
433             ) {
434                 p->real_cred = get_cred(p->cred);
435                 get_cred(p->cred);
436                 alter_cred_subscribers(p->cred, 2);
437                 kdebug("share_creds(%p{%d,%d})",
438                        p->cred, atomic_read(&p->cred->usage),
439                        read_cred_subscribers(p->cred));
440                 atomic_inc(&p->cred->user->processes);
441                 return 0;
442         }
443
444         new = prepare_creds();
445         if (!new)
446                 return -ENOMEM;
447
448         if (clone_flags & CLONE_NEWUSER) {
449                 ret = create_user_ns(new);
450                 if (ret < 0)
451                         goto error_put;
452         }
453
454 #ifdef CONFIG_KEYS
455         /* new threads get their own thread keyrings if their parent already
456          * had one */
457         if (new->thread_keyring) {
458                 key_put(new->thread_keyring);
459                 new->thread_keyring = NULL;
460                 if (clone_flags & CLONE_THREAD)
461                         install_thread_keyring_to_cred(new);
462         }
463
464         /* we share the process and session keyrings between all the threads in
465          * a process - this is slightly icky as we violate COW credentials a
466          * bit */
467         if (!(clone_flags & CLONE_THREAD)) {
468                 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
469                 if (!tgcred) {
470                         ret = -ENOMEM;
471                         goto error_put;
472                 }
473                 atomic_set(&tgcred->usage, 1);
474                 spin_lock_init(&tgcred->lock);
475                 tgcred->process_keyring = NULL;
476                 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
477
478                 release_tgcred(new);
479                 new->tgcred = tgcred;
480         }
481 #endif
482
483         atomic_inc(&new->user->processes);
484         p->cred = p->real_cred = get_cred(new);
485         alter_cred_subscribers(new, 2);
486         validate_creds(new);
487         return 0;
488
489 error_put:
490         put_cred(new);
491         return ret;
492 }
493
494 /**
495  * commit_creds - Install new credentials upon the current task
496  * @new: The credentials to be assigned
497  *
498  * Install a new set of credentials to the current task, using RCU to replace
499  * the old set.  Both the objective and the subjective credentials pointers are
500  * updated.  This function may not be called if the subjective credentials are
501  * in an overridden state.
502  *
503  * This function eats the caller's reference to the new credentials.
504  *
505  * Always returns 0 thus allowing this function to be tail-called at the end
506  * of, say, sys_setgid().
507  */
508 int commit_creds(struct cred *new)
509 {
510         struct task_struct *task = current;
511         const struct cred *old = task->real_cred;
512
513         kdebug("commit_creds(%p{%d,%d})", new,
514                atomic_read(&new->usage),
515                read_cred_subscribers(new));
516
517         BUG_ON(task->cred != old);
518 #ifdef CONFIG_DEBUG_CREDENTIALS
519         BUG_ON(read_cred_subscribers(old) < 2);
520         validate_creds(old);
521         validate_creds(new);
522 #endif
523         BUG_ON(atomic_read(&new->usage) < 1);
524
525         get_cred(new); /* we will require a ref for the subj creds too */
526
527         /* dumpability changes */
528         if (old->euid != new->euid ||
529             old->egid != new->egid ||
530             old->fsuid != new->fsuid ||
531             old->fsgid != new->fsgid ||
532             !cap_issubset(new->cap_permitted, old->cap_permitted)) {
533                 if (task->mm)
534                         set_dumpable(task->mm, suid_dumpable);
535                 task->pdeath_signal = 0;
536                 smp_wmb();
537         }
538
539         /* alter the thread keyring */
540         if (new->fsuid != old->fsuid)
541                 key_fsuid_changed(task);
542         if (new->fsgid != old->fsgid)
543                 key_fsgid_changed(task);
544
545         /* do it
546          * - What if a process setreuid()'s and this brings the
547          *   new uid over his NPROC rlimit?  We can check this now
548          *   cheaply with the new uid cache, so if it matters
549          *   we should be checking for it.  -DaveM
550          */
551         alter_cred_subscribers(new, 2);
552         if (new->user != old->user)
553                 atomic_inc(&new->user->processes);
554         rcu_assign_pointer(task->real_cred, new);
555         rcu_assign_pointer(task->cred, new);
556         if (new->user != old->user)
557                 atomic_dec(&old->user->processes);
558         alter_cred_subscribers(old, -2);
559
560         /* send notifications */
561         if (new->uid   != old->uid  ||
562             new->euid  != old->euid ||
563             new->suid  != old->suid ||
564             new->fsuid != old->fsuid)
565                 proc_id_connector(task, PROC_EVENT_UID);
566
567         if (new->gid   != old->gid  ||
568             new->egid  != old->egid ||
569             new->sgid  != old->sgid ||
570             new->fsgid != old->fsgid)
571                 proc_id_connector(task, PROC_EVENT_GID);
572
573         /* release the old obj and subj refs both */
574         put_cred(old);
575         put_cred(old);
576         return 0;
577 }
578 EXPORT_SYMBOL(commit_creds);
579
580 /**
581  * abort_creds - Discard a set of credentials and unlock the current task
582  * @new: The credentials that were going to be applied
583  *
584  * Discard a set of credentials that were under construction and unlock the
585  * current task.
586  */
587 void abort_creds(struct cred *new)
588 {
589         kdebug("abort_creds(%p{%d,%d})", new,
590                atomic_read(&new->usage),
591                read_cred_subscribers(new));
592
593 #ifdef CONFIG_DEBUG_CREDENTIALS
594         BUG_ON(read_cred_subscribers(new) != 0);
595 #endif
596         BUG_ON(atomic_read(&new->usage) < 1);
597         put_cred(new);
598 }
599 EXPORT_SYMBOL(abort_creds);
600
601 /**
602  * override_creds - Override the current process's subjective credentials
603  * @new: The credentials to be assigned
604  *
605  * Install a set of temporary override subjective credentials on the current
606  * process, returning the old set for later reversion.
607  */
608 const struct cred *override_creds(const struct cred *new)
609 {
610         const struct cred *old = current->cred;
611
612         kdebug("override_creds(%p{%d,%d})", new,
613                atomic_read(&new->usage),
614                read_cred_subscribers(new));
615
616         validate_creds(old);
617         validate_creds(new);
618         get_cred(new);
619         alter_cred_subscribers(new, 1);
620         rcu_assign_pointer(current->cred, new);
621         alter_cred_subscribers(old, -1);
622
623         kdebug("override_creds() = %p{%d,%d}", old,
624                atomic_read(&old->usage),
625                read_cred_subscribers(old));
626         return old;
627 }
628 EXPORT_SYMBOL(override_creds);
629
630 /**
631  * revert_creds - Revert a temporary subjective credentials override
632  * @old: The credentials to be restored
633  *
634  * Revert a temporary set of override subjective credentials to an old set,
635  * discarding the override set.
636  */
637 void revert_creds(const struct cred *old)
638 {
639         const struct cred *override = current->cred;
640
641         kdebug("revert_creds(%p{%d,%d})", old,
642                atomic_read(&old->usage),
643                read_cred_subscribers(old));
644
645         validate_creds(old);
646         validate_creds(override);
647         alter_cred_subscribers(old, 1);
648         rcu_assign_pointer(current->cred, old);
649         alter_cred_subscribers(override, -1);
650         put_cred(override);
651 }
652 EXPORT_SYMBOL(revert_creds);
653
654 /*
655  * initialise the credentials stuff
656  */
657 void __init cred_init(void)
658 {
659         /* allocate a slab in which we can store credentials */
660         cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
661                                      0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
662 }
663
664 /**
665  * prepare_kernel_cred - Prepare a set of credentials for a kernel service
666  * @daemon: A userspace daemon to be used as a reference
667  *
668  * Prepare a set of credentials for a kernel service.  This can then be used to
669  * override a task's own credentials so that work can be done on behalf of that
670  * task that requires a different subjective context.
671  *
672  * @daemon is used to provide a base for the security record, but can be NULL.
673  * If @daemon is supplied, then the security data will be derived from that;
674  * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
675  *
676  * The caller may change these controls afterwards if desired.
677  *
678  * Returns the new credentials or NULL if out of memory.
679  *
680  * Does not take, and does not return holding current->cred_replace_mutex.
681  */
682 struct cred *prepare_kernel_cred(struct task_struct *daemon)
683 {
684         const struct cred *old;
685         struct cred *new;
686
687         new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
688         if (!new)
689                 return NULL;
690
691         kdebug("prepare_kernel_cred() alloc %p", new);
692
693         if (daemon)
694                 old = get_task_cred(daemon);
695         else
696                 old = get_cred(&init_cred);
697
698         validate_creds(old);
699
700         *new = *old;
701         get_uid(new->user);
702         get_group_info(new->group_info);
703
704 #ifdef CONFIG_KEYS
705         atomic_inc(&init_tgcred.usage);
706         new->tgcred = &init_tgcred;
707         new->request_key_auth = NULL;
708         new->thread_keyring = NULL;
709         new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
710 #endif
711
712 #ifdef CONFIG_SECURITY
713         new->security = NULL;
714 #endif
715         if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
716                 goto error;
717
718         atomic_set(&new->usage, 1);
719         set_cred_subscribers(new, 0);
720         put_cred(old);
721         validate_creds(new);
722         return new;
723
724 error:
725         put_cred(new);
726         put_cred(old);
727         return NULL;
728 }
729 EXPORT_SYMBOL(prepare_kernel_cred);
730
731 /**
732  * set_security_override - Set the security ID in a set of credentials
733  * @new: The credentials to alter
734  * @secid: The LSM security ID to set
735  *
736  * Set the LSM security ID in a set of credentials so that the subjective
737  * security is overridden when an alternative set of credentials is used.
738  */
739 int set_security_override(struct cred *new, u32 secid)
740 {
741         return security_kernel_act_as(new, secid);
742 }
743 EXPORT_SYMBOL(set_security_override);
744
745 /**
746  * set_security_override_from_ctx - Set the security ID in a set of credentials
747  * @new: The credentials to alter
748  * @secctx: The LSM security context to generate the security ID from.
749  *
750  * Set the LSM security ID in a set of credentials so that the subjective
751  * security is overridden when an alternative set of credentials is used.  The
752  * security ID is specified in string form as a security context to be
753  * interpreted by the LSM.
754  */
755 int set_security_override_from_ctx(struct cred *new, const char *secctx)
756 {
757         u32 secid;
758         int ret;
759
760         ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
761         if (ret < 0)
762                 return ret;
763
764         return set_security_override(new, secid);
765 }
766 EXPORT_SYMBOL(set_security_override_from_ctx);
767
768 /**
769  * set_create_files_as - Set the LSM file create context in a set of credentials
770  * @new: The credentials to alter
771  * @inode: The inode to take the context from
772  *
773  * Change the LSM file creation context in a set of credentials to be the same
774  * as the object context of the specified inode, so that the new inodes have
775  * the same MAC context as that inode.
776  */
777 int set_create_files_as(struct cred *new, struct inode *inode)
778 {
779         new->fsuid = inode->i_uid;
780         new->fsgid = inode->i_gid;
781         return security_kernel_create_files_as(new, inode);
782 }
783 EXPORT_SYMBOL(set_create_files_as);
784
785 #ifdef CONFIG_DEBUG_CREDENTIALS
786
787 bool creds_are_invalid(const struct cred *cred)
788 {
789         if (cred->magic != CRED_MAGIC)
790                 return true;
791 #ifdef CONFIG_SECURITY_SELINUX
792         if (selinux_is_enabled()) {
793                 if ((unsigned long) cred->security < PAGE_SIZE)
794                         return true;
795                 if ((*(u32 *)cred->security & 0xffffff00) ==
796                     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
797                         return true;
798         }
799 #endif
800         return false;
801 }
802 EXPORT_SYMBOL(creds_are_invalid);
803
804 /*
805  * dump invalid credentials
806  */
807 static void dump_invalid_creds(const struct cred *cred, const char *label,
808                                const struct task_struct *tsk)
809 {
810         printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
811                label, cred,
812                cred == &init_cred ? "[init]" : "",
813                cred == tsk->real_cred ? "[real]" : "",
814                cred == tsk->cred ? "[eff]" : "");
815         printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
816                cred->magic, cred->put_addr);
817         printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
818                atomic_read(&cred->usage),
819                read_cred_subscribers(cred));
820         printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
821                cred->uid, cred->euid, cred->suid, cred->fsuid);
822         printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
823                cred->gid, cred->egid, cred->sgid, 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  */
838 void __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 }
845 EXPORT_SYMBOL(__invalid_creds);
846
847 /*
848  * check the credentials on a process
849  */
850 void __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
866 invalid_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 }
877 EXPORT_SYMBOL(__validate_process_creds);
878
879 /*
880  * check creds for do_exit()
881  */
882 void 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 */