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