Root/kernel/cred.c

1/* Task credentials management - see Documentation/security/credentials.txt
2 *
3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11#include <linux/export.h>
12#include <linux/cred.h>
13#include <linux/slab.h>
14#include <linux/sched.h>
15#include <linux/key.h>
16#include <linux/keyctl.h>
17#include <linux/init_task.h>
18#include <linux/security.h>
19#include <linux/binfmts.h>
20#include <linux/cn_proc.h>
21
22#if 0
23#define kdebug(FMT, ...) \
24    printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
25#else
26#define kdebug(FMT, ...) \
27    no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
28#endif
29
30static struct kmem_cache *cred_jar;
31
32/*
33 * The common credentials for the initial task's thread group
34 */
35#ifdef CONFIG_KEYS
36static struct thread_group_cred init_tgcred = {
37    .usage = ATOMIC_INIT(2),
38    .tgid = 0,
39    .lock = __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock),
40};
41#endif
42
43/*
44 * The initial credentials for the initial task
45 */
46struct cred init_cred = {
47    .usage = ATOMIC_INIT(4),
48#ifdef CONFIG_DEBUG_CREDENTIALS
49    .subscribers = ATOMIC_INIT(2),
50    .magic = CRED_MAGIC,
51#endif
52    .uid = GLOBAL_ROOT_UID,
53    .gid = GLOBAL_ROOT_GID,
54    .suid = GLOBAL_ROOT_UID,
55    .sgid = GLOBAL_ROOT_GID,
56    .euid = GLOBAL_ROOT_UID,
57    .egid = GLOBAL_ROOT_GID,
58    .fsuid = GLOBAL_ROOT_UID,
59    .fsgid = GLOBAL_ROOT_GID,
60    .securebits = SECUREBITS_DEFAULT,
61    .cap_inheritable = CAP_EMPTY_SET,
62    .cap_permitted = CAP_FULL_SET,
63    .cap_effective = CAP_FULL_SET,
64    .cap_bset = CAP_FULL_SET,
65    .user = INIT_USER,
66    .user_ns = &init_user_ns,
67    .group_info = &init_groups,
68#ifdef CONFIG_KEYS
69    .tgcred = &init_tgcred,
70#endif
71};
72
73static inline void set_cred_subscribers(struct cred *cred, int n)
74{
75#ifdef CONFIG_DEBUG_CREDENTIALS
76    atomic_set(&cred->subscribers, n);
77#endif
78}
79
80static inline int read_cred_subscribers(const struct cred *cred)
81{
82#ifdef CONFIG_DEBUG_CREDENTIALS
83    return atomic_read(&cred->subscribers);
84#else
85    return 0;
86#endif
87}
88
89static inline void alter_cred_subscribers(const struct cred *_cred, int n)
90{
91#ifdef CONFIG_DEBUG_CREDENTIALS
92    struct cred *cred = (struct cred *) _cred;
93
94    atomic_add(n, &cred->subscribers);
95#endif
96}
97
98/*
99 * Dispose of the shared task group credentials
100 */
101#ifdef CONFIG_KEYS
102static void release_tgcred_rcu(struct rcu_head *rcu)
103{
104    struct thread_group_cred *tgcred =
105        container_of(rcu, struct thread_group_cred, rcu);
106
107    BUG_ON(atomic_read(&tgcred->usage) != 0);
108
109    key_put(tgcred->session_keyring);
110    key_put(tgcred->process_keyring);
111    kfree(tgcred);
112}
113#endif
114
115/*
116 * Release a set of thread group credentials.
117 */
118static void release_tgcred(struct cred *cred)
119{
120#ifdef CONFIG_KEYS
121    struct thread_group_cred *tgcred = cred->tgcred;
122
123    if (atomic_dec_and_test(&tgcred->usage))
124        call_rcu(&tgcred->rcu, release_tgcred_rcu);
125#endif
126}
127
128/*
129 * The RCU callback to actually dispose of a set of credentials
130 */
131static void put_cred_rcu(struct rcu_head *rcu)
132{
133    struct cred *cred = container_of(rcu, struct cred, rcu);
134
135    kdebug("put_cred_rcu(%p)", cred);
136
137#ifdef CONFIG_DEBUG_CREDENTIALS
138    if (cred->magic != CRED_MAGIC_DEAD ||
139        atomic_read(&cred->usage) != 0 ||
140        read_cred_subscribers(cred) != 0)
141        panic("CRED: put_cred_rcu() sees %p with"
142              " mag %x, put %p, usage %d, subscr %d\n",
143              cred, cred->magic, cred->put_addr,
144              atomic_read(&cred->usage),
145              read_cred_subscribers(cred));
146#else
147    if (atomic_read(&cred->usage) != 0)
148        panic("CRED: put_cred_rcu() sees %p with usage %d\n",
149              cred, atomic_read(&cred->usage));
150#endif
151
152    security_cred_free(cred);
153    key_put(cred->thread_keyring);
154    key_put(cred->request_key_auth);
155    release_tgcred(cred);
156    if (cred->group_info)
157        put_group_info(cred->group_info);
158    free_uid(cred->user);
159    put_user_ns(cred->user_ns);
160    kmem_cache_free(cred_jar, cred);
161}
162
163/**
164 * __put_cred - Destroy a set of credentials
165 * @cred: The record to release
166 *
167 * Destroy a set of credentials on which no references remain.
168 */
169void __put_cred(struct cred *cred)
170{
171    kdebug("__put_cred(%p{%d,%d})", cred,
172           atomic_read(&cred->usage),
173           read_cred_subscribers(cred));
174
175    BUG_ON(atomic_read(&cred->usage) != 0);
176#ifdef CONFIG_DEBUG_CREDENTIALS
177    BUG_ON(read_cred_subscribers(cred) != 0);
178    cred->magic = CRED_MAGIC_DEAD;
179    cred->put_addr = __builtin_return_address(0);
180#endif
181    BUG_ON(cred == current->cred);
182    BUG_ON(cred == current->real_cred);
183
184    call_rcu(&cred->rcu, put_cred_rcu);
185}
186EXPORT_SYMBOL(__put_cred);
187
188/*
189 * Clean up a task's credentials when it exits
190 */
191void exit_creds(struct task_struct *tsk)
192{
193    struct cred *cred;
194
195    kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
196           atomic_read(&tsk->cred->usage),
197           read_cred_subscribers(tsk->cred));
198
199    cred = (struct cred *) tsk->real_cred;
200    tsk->real_cred = NULL;
201    validate_creds(cred);
202    alter_cred_subscribers(cred, -1);
203    put_cred(cred);
204
205    cred = (struct cred *) tsk->cred;
206    tsk->cred = NULL;
207    validate_creds(cred);
208    alter_cred_subscribers(cred, -1);
209    put_cred(cred);
210}
211
212/**
213 * get_task_cred - Get another task's objective credentials
214 * @task: The task to query
215 *
216 * Get the objective credentials of a task, pinning them so that they can't go
217 * away. Accessing a task's credentials directly is not permitted.
218 *
219 * The caller must also make sure task doesn't get deleted, either by holding a
220 * ref on task or by holding tasklist_lock to prevent it from being unlinked.
221 */
222const struct cred *get_task_cred(struct task_struct *task)
223{
224    const struct cred *cred;
225
226    rcu_read_lock();
227
228    do {
229        cred = __task_cred((task));
230        BUG_ON(!cred);
231    } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
232
233    rcu_read_unlock();
234    return cred;
235}
236
237/*
238 * Allocate blank credentials, such that the credentials can be filled in at a
239 * later date without risk of ENOMEM.
240 */
241struct cred *cred_alloc_blank(void)
242{
243    struct cred *new;
244
245    new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
246    if (!new)
247        return NULL;
248
249#ifdef CONFIG_KEYS
250    new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
251    if (!new->tgcred) {
252        kmem_cache_free(cred_jar, new);
253        return NULL;
254    }
255    atomic_set(&new->tgcred->usage, 1);
256#endif
257
258    atomic_set(&new->usage, 1);
259#ifdef CONFIG_DEBUG_CREDENTIALS
260    new->magic = CRED_MAGIC;
261#endif
262
263    if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
264        goto error;
265
266    return new;
267
268error:
269    abort_creds(new);
270    return NULL;
271}
272
273/**
274 * prepare_creds - Prepare a new set of credentials for modification
275 *
276 * Prepare a new set of task credentials for modification. A task's creds
277 * shouldn't generally be modified directly, therefore this function is used to
278 * prepare a new copy, which the caller then modifies and then commits by
279 * calling commit_creds().
280 *
281 * Preparation involves making a copy of the objective creds for modification.
282 *
283 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
284 *
285 * Call commit_creds() or abort_creds() to clean up.
286 */
287struct cred *prepare_creds(void)
288{
289    struct task_struct *task = current;
290    const struct cred *old;
291    struct cred *new;
292
293    validate_process_creds();
294
295    new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
296    if (!new)
297        return NULL;
298
299    kdebug("prepare_creds() alloc %p", new);
300
301    old = task->cred;
302    memcpy(new, old, sizeof(struct cred));
303
304    atomic_set(&new->usage, 1);
305    set_cred_subscribers(new, 0);
306    get_group_info(new->group_info);
307    get_uid(new->user);
308    get_user_ns(new->user_ns);
309
310#ifdef CONFIG_KEYS
311    key_get(new->thread_keyring);
312    key_get(new->request_key_auth);
313    atomic_inc(&new->tgcred->usage);
314#endif
315
316#ifdef CONFIG_SECURITY
317    new->security = NULL;
318#endif
319
320    if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
321        goto error;
322    validate_creds(new);
323    return new;
324
325error:
326    abort_creds(new);
327    return NULL;
328}
329EXPORT_SYMBOL(prepare_creds);
330
331/*
332 * Prepare credentials for current to perform an execve()
333 * - The caller must hold ->cred_guard_mutex
334 */
335struct cred *prepare_exec_creds(void)
336{
337    struct thread_group_cred *tgcred = NULL;
338    struct cred *new;
339
340#ifdef CONFIG_KEYS
341    tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
342    if (!tgcred)
343        return NULL;
344#endif
345
346    new = prepare_creds();
347    if (!new) {
348        kfree(tgcred);
349        return new;
350    }
351
352#ifdef CONFIG_KEYS
353    /* newly exec'd tasks don't get a thread keyring */
354    key_put(new->thread_keyring);
355    new->thread_keyring = NULL;
356
357    /* create a new per-thread-group creds for all this set of threads to
358     * share */
359    memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
360
361    atomic_set(&tgcred->usage, 1);
362    spin_lock_init(&tgcred->lock);
363
364    /* inherit the session keyring; new process keyring */
365    key_get(tgcred->session_keyring);
366    tgcred->process_keyring = NULL;
367
368    release_tgcred(new);
369    new->tgcred = tgcred;
370#endif
371
372    return new;
373}
374
375/*
376 * Copy credentials for the new process created by fork()
377 *
378 * We share if we can, but under some circumstances we have to generate a new
379 * set.
380 *
381 * The new process gets the current process's subjective credentials as its
382 * objective and subjective credentials
383 */
384int copy_creds(struct task_struct *p, unsigned long clone_flags)
385{
386#ifdef CONFIG_KEYS
387    struct thread_group_cred *tgcred;
388#endif
389    struct cred *new;
390    int ret;
391
392    if (
393#ifdef CONFIG_KEYS
394        !p->cred->thread_keyring &&
395#endif
396        clone_flags & CLONE_THREAD
397        ) {
398        p->real_cred = get_cred(p->cred);
399        get_cred(p->cred);
400        alter_cred_subscribers(p->cred, 2);
401        kdebug("share_creds(%p{%d,%d})",
402               p->cred, atomic_read(&p->cred->usage),
403               read_cred_subscribers(p->cred));
404        atomic_inc(&p->cred->user->processes);
405        return 0;
406    }
407
408    new = prepare_creds();
409    if (!new)
410        return -ENOMEM;
411
412    if (clone_flags & CLONE_NEWUSER) {
413        ret = create_user_ns(new);
414        if (ret < 0)
415            goto error_put;
416    }
417
418#ifdef CONFIG_KEYS
419    /* new threads get their own thread keyrings if their parent already
420     * had one */
421    if (new->thread_keyring) {
422        key_put(new->thread_keyring);
423        new->thread_keyring = NULL;
424        if (clone_flags & CLONE_THREAD)
425            install_thread_keyring_to_cred(new);
426    }
427
428    /* we share the process and session keyrings between all the threads in
429     * a process - this is slightly icky as we violate COW credentials a
430     * bit */
431    if (!(clone_flags & CLONE_THREAD)) {
432        tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
433        if (!tgcred) {
434            ret = -ENOMEM;
435            goto error_put;
436        }
437        atomic_set(&tgcred->usage, 1);
438        spin_lock_init(&tgcred->lock);
439        tgcred->process_keyring = NULL;
440        tgcred->session_keyring = key_get(new->tgcred->session_keyring);
441
442        release_tgcred(new);
443        new->tgcred = tgcred;
444    }
445#endif
446
447    atomic_inc(&new->user->processes);
448    p->cred = p->real_cred = get_cred(new);
449    alter_cred_subscribers(new, 2);
450    validate_creds(new);
451    return 0;
452
453error_put:
454    put_cred(new);
455    return ret;
456}
457
458/**
459 * commit_creds - Install new credentials upon the current task
460 * @new: The credentials to be assigned
461 *
462 * Install a new set of credentials to the current task, using RCU to replace
463 * the old set. Both the objective and the subjective credentials pointers are
464 * updated. This function may not be called if the subjective credentials are
465 * in an overridden state.
466 *
467 * This function eats the caller's reference to the new credentials.
468 *
469 * Always returns 0 thus allowing this function to be tail-called at the end
470 * of, say, sys_setgid().
471 */
472int commit_creds(struct cred *new)
473{
474    struct task_struct *task = current;
475    const struct cred *old = task->real_cred;
476
477    kdebug("commit_creds(%p{%d,%d})", new,
478           atomic_read(&new->usage),
479           read_cred_subscribers(new));
480
481    BUG_ON(task->cred != old);
482#ifdef CONFIG_DEBUG_CREDENTIALS
483    BUG_ON(read_cred_subscribers(old) < 2);
484    validate_creds(old);
485    validate_creds(new);
486#endif
487    BUG_ON(atomic_read(&new->usage) < 1);
488
489    get_cred(new); /* we will require a ref for the subj creds too */
490
491    /* dumpability changes */
492    if (!uid_eq(old->euid, new->euid) ||
493        !gid_eq(old->egid, new->egid) ||
494        !uid_eq(old->fsuid, new->fsuid) ||
495        !gid_eq(old->fsgid, new->fsgid) ||
496        !cap_issubset(new->cap_permitted, old->cap_permitted)) {
497        if (task->mm)
498            set_dumpable(task->mm, suid_dumpable);
499        task->pdeath_signal = 0;
500        smp_wmb();
501    }
502
503    /* alter the thread keyring */
504    if (!uid_eq(new->fsuid, old->fsuid))
505        key_fsuid_changed(task);
506    if (!gid_eq(new->fsgid, old->fsgid))
507        key_fsgid_changed(task);
508
509    /* do it
510     * RLIMIT_NPROC limits on user->processes have already been checked
511     * in set_user().
512     */
513    alter_cred_subscribers(new, 2);
514    if (new->user != old->user)
515        atomic_inc(&new->user->processes);
516    rcu_assign_pointer(task->real_cred, new);
517    rcu_assign_pointer(task->cred, new);
518    if (new->user != old->user)
519        atomic_dec(&old->user->processes);
520    alter_cred_subscribers(old, -2);
521
522    /* send notifications */
523    if (!uid_eq(new->uid, old->uid) ||
524        !uid_eq(new->euid, old->euid) ||
525        !uid_eq(new->suid, old->suid) ||
526        !uid_eq(new->fsuid, old->fsuid))
527        proc_id_connector(task, PROC_EVENT_UID);
528
529    if (!gid_eq(new->gid, old->gid) ||
530        !gid_eq(new->egid, old->egid) ||
531        !gid_eq(new->sgid, old->sgid) ||
532        !gid_eq(new->fsgid, old->fsgid))
533        proc_id_connector(task, PROC_EVENT_GID);
534
535    /* release the old obj and subj refs both */
536    put_cred(old);
537    put_cred(old);
538    return 0;
539}
540EXPORT_SYMBOL(commit_creds);
541
542/**
543 * abort_creds - Discard a set of credentials and unlock the current task
544 * @new: The credentials that were going to be applied
545 *
546 * Discard a set of credentials that were under construction and unlock the
547 * current task.
548 */
549void abort_creds(struct cred *new)
550{
551    kdebug("abort_creds(%p{%d,%d})", new,
552           atomic_read(&new->usage),
553           read_cred_subscribers(new));
554
555#ifdef CONFIG_DEBUG_CREDENTIALS
556    BUG_ON(read_cred_subscribers(new) != 0);
557#endif
558    BUG_ON(atomic_read(&new->usage) < 1);
559    put_cred(new);
560}
561EXPORT_SYMBOL(abort_creds);
562
563/**
564 * override_creds - Override the current process's subjective credentials
565 * @new: The credentials to be assigned
566 *
567 * Install a set of temporary override subjective credentials on the current
568 * process, returning the old set for later reversion.
569 */
570const struct cred *override_creds(const struct cred *new)
571{
572    const struct cred *old = current->cred;
573
574    kdebug("override_creds(%p{%d,%d})", new,
575           atomic_read(&new->usage),
576           read_cred_subscribers(new));
577
578    validate_creds(old);
579    validate_creds(new);
580    get_cred(new);
581    alter_cred_subscribers(new, 1);
582    rcu_assign_pointer(current->cred, new);
583    alter_cred_subscribers(old, -1);
584
585    kdebug("override_creds() = %p{%d,%d}", old,
586           atomic_read(&old->usage),
587           read_cred_subscribers(old));
588    return old;
589}
590EXPORT_SYMBOL(override_creds);
591
592/**
593 * revert_creds - Revert a temporary subjective credentials override
594 * @old: The credentials to be restored
595 *
596 * Revert a temporary set of override subjective credentials to an old set,
597 * discarding the override set.
598 */
599void revert_creds(const struct cred *old)
600{
601    const struct cred *override = current->cred;
602
603    kdebug("revert_creds(%p{%d,%d})", old,
604           atomic_read(&old->usage),
605           read_cred_subscribers(old));
606
607    validate_creds(old);
608    validate_creds(override);
609    alter_cred_subscribers(old, 1);
610    rcu_assign_pointer(current->cred, old);
611    alter_cred_subscribers(override, -1);
612    put_cred(override);
613}
614EXPORT_SYMBOL(revert_creds);
615
616/*
617 * initialise the credentials stuff
618 */
619void __init cred_init(void)
620{
621    /* allocate a slab in which we can store credentials */
622    cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
623                     0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
624}
625
626/**
627 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
628 * @daemon: A userspace daemon to be used as a reference
629 *
630 * Prepare a set of credentials for a kernel service. This can then be used to
631 * override a task's own credentials so that work can be done on behalf of that
632 * task that requires a different subjective context.
633 *
634 * @daemon is used to provide a base for the security record, but can be NULL.
635 * If @daemon is supplied, then the security data will be derived from that;
636 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
637 *
638 * The caller may change these controls afterwards if desired.
639 *
640 * Returns the new credentials or NULL if out of memory.
641 *
642 * Does not take, and does not return holding current->cred_replace_mutex.
643 */
644struct cred *prepare_kernel_cred(struct task_struct *daemon)
645{
646#ifdef CONFIG_KEYS
647    struct thread_group_cred *tgcred;
648#endif
649    const struct cred *old;
650    struct cred *new;
651
652    new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
653    if (!new)
654        return NULL;
655
656#ifdef CONFIG_KEYS
657    tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
658    if (!tgcred) {
659        kmem_cache_free(cred_jar, new);
660        return NULL;
661    }
662#endif
663
664    kdebug("prepare_kernel_cred() alloc %p", new);
665
666    if (daemon)
667        old = get_task_cred(daemon);
668    else
669        old = get_cred(&init_cred);
670
671    validate_creds(old);
672
673    *new = *old;
674    atomic_set(&new->usage, 1);
675    set_cred_subscribers(new, 0);
676    get_uid(new->user);
677    get_user_ns(new->user_ns);
678    get_group_info(new->group_info);
679
680#ifdef CONFIG_KEYS
681    atomic_set(&tgcred->usage, 1);
682    spin_lock_init(&tgcred->lock);
683    tgcred->process_keyring = NULL;
684    tgcred->session_keyring = NULL;
685    new->tgcred = tgcred;
686    new->request_key_auth = NULL;
687    new->thread_keyring = NULL;
688    new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
689#endif
690
691#ifdef CONFIG_SECURITY
692    new->security = NULL;
693#endif
694    if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
695        goto error;
696
697    put_cred(old);
698    validate_creds(new);
699    return new;
700
701error:
702    put_cred(new);
703    put_cred(old);
704    return NULL;
705}
706EXPORT_SYMBOL(prepare_kernel_cred);
707
708/**
709 * set_security_override - Set the security ID in a set of credentials
710 * @new: The credentials to alter
711 * @secid: The LSM security ID to set
712 *
713 * Set the LSM security ID in a set of credentials so that the subjective
714 * security is overridden when an alternative set of credentials is used.
715 */
716int set_security_override(struct cred *new, u32 secid)
717{
718    return security_kernel_act_as(new, secid);
719}
720EXPORT_SYMBOL(set_security_override);
721
722/**
723 * set_security_override_from_ctx - Set the security ID in a set of credentials
724 * @new: The credentials to alter
725 * @secctx: The LSM security context to generate the security ID from.
726 *
727 * Set the LSM security ID in a set of credentials so that the subjective
728 * security is overridden when an alternative set of credentials is used. The
729 * security ID is specified in string form as a security context to be
730 * interpreted by the LSM.
731 */
732int set_security_override_from_ctx(struct cred *new, const char *secctx)
733{
734    u32 secid;
735    int ret;
736
737    ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
738    if (ret < 0)
739        return ret;
740
741    return set_security_override(new, secid);
742}
743EXPORT_SYMBOL(set_security_override_from_ctx);
744
745/**
746 * set_create_files_as - Set the LSM file create context in a set of credentials
747 * @new: The credentials to alter
748 * @inode: The inode to take the context from
749 *
750 * Change the LSM file creation context in a set of credentials to be the same
751 * as the object context of the specified inode, so that the new inodes have
752 * the same MAC context as that inode.
753 */
754int set_create_files_as(struct cred *new, struct inode *inode)
755{
756    new->fsuid = inode->i_uid;
757    new->fsgid = inode->i_gid;
758    return security_kernel_create_files_as(new, inode);
759}
760EXPORT_SYMBOL(set_create_files_as);
761
762#ifdef CONFIG_DEBUG_CREDENTIALS
763
764bool creds_are_invalid(const struct cred *cred)
765{
766    if (cred->magic != CRED_MAGIC)
767        return true;
768#ifdef CONFIG_SECURITY_SELINUX
769    /*
770     * cred->security == NULL if security_cred_alloc_blank() or
771     * security_prepare_creds() returned an error.
772     */
773    if (selinux_is_enabled() && cred->security) {
774        if ((unsigned long) cred->security < PAGE_SIZE)
775            return true;
776        if ((*(u32 *)cred->security & 0xffffff00) ==
777            (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
778            return true;
779    }
780#endif
781    return false;
782}
783EXPORT_SYMBOL(creds_are_invalid);
784
785/*
786 * dump invalid credentials
787 */
788static void dump_invalid_creds(const struct cred *cred, const char *label,
789                   const struct task_struct *tsk)
790{
791    printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
792           label, cred,
793           cred == &init_cred ? "[init]" : "",
794           cred == tsk->real_cred ? "[real]" : "",
795           cred == tsk->cred ? "[eff]" : "");
796    printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
797           cred->magic, cred->put_addr);
798    printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
799           atomic_read(&cred->usage),
800           read_cred_subscribers(cred));
801    printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
802           cred->uid, cred->euid, cred->suid, cred->fsuid);
803    printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
804           cred->gid, cred->egid, cred->sgid, cred->fsgid);
805#ifdef CONFIG_SECURITY
806    printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
807    if ((unsigned long) cred->security >= PAGE_SIZE &&
808        (((unsigned long) cred->security & 0xffffff00) !=
809         (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
810        printk(KERN_ERR "CRED: ->security {%x, %x}\n",
811               ((u32*)cred->security)[0],
812               ((u32*)cred->security)[1]);
813#endif
814}
815
816/*
817 * report use of invalid credentials
818 */
819void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
820{
821    printk(KERN_ERR "CRED: Invalid credentials\n");
822    printk(KERN_ERR "CRED: At %s:%u\n", file, line);
823    dump_invalid_creds(cred, "Specified", current);
824    BUG();
825}
826EXPORT_SYMBOL(__invalid_creds);
827
828/*
829 * check the credentials on a process
830 */
831void __validate_process_creds(struct task_struct *tsk,
832                  const char *file, unsigned line)
833{
834    if (tsk->cred == tsk->real_cred) {
835        if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
836                 creds_are_invalid(tsk->cred)))
837            goto invalid_creds;
838    } else {
839        if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
840                 read_cred_subscribers(tsk->cred) < 1 ||
841                 creds_are_invalid(tsk->real_cred) ||
842                 creds_are_invalid(tsk->cred)))
843            goto invalid_creds;
844    }
845    return;
846
847invalid_creds:
848    printk(KERN_ERR "CRED: Invalid process credentials\n");
849    printk(KERN_ERR "CRED: At %s:%u\n", file, line);
850
851    dump_invalid_creds(tsk->real_cred, "Real", tsk);
852    if (tsk->cred != tsk->real_cred)
853        dump_invalid_creds(tsk->cred, "Effective", tsk);
854    else
855        printk(KERN_ERR "CRED: Effective creds == Real creds\n");
856    BUG();
857}
858EXPORT_SYMBOL(__validate_process_creds);
859
860/*
861 * check creds for do_exit()
862 */
863void validate_creds_for_do_exit(struct task_struct *tsk)
864{
865    kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
866           tsk->real_cred, tsk->cred,
867           atomic_read(&tsk->cred->usage),
868           read_cred_subscribers(tsk->cred));
869
870    __validate_process_creds(tsk, __FILE__, __LINE__);
871}
872
873#endif /* CONFIG_DEBUG_CREDENTIALS */
874

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