1 /* Task credentials management - see Documentation/credentials.txt
3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
11 #include <linux/module.h>
12 #include <linux/cred.h>
13 #include <linux/sched.h>
14 #include <linux/key.h>
15 #include <linux/keyctl.h>
16 #include <linux/init_task.h>
17 #include <linux/security.h>
18 #include <linux/cn_proc.h>
19 #include "cred-internals.h"
22 #define kdebug(FMT, ...) \
23 printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
25 static inline __attribute__((format(printf
, 1, 2)))
26 void no_printk(const char *fmt
, ...)
29 #define kdebug(FMT, ...) \
30 no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
33 static struct kmem_cache
*cred_jar
;
36 * The common credentials for the initial task's thread group
39 static struct thread_group_cred init_tgcred
= {
40 .usage
= ATOMIC_INIT(2),
42 .lock
= SPIN_LOCK_UNLOCKED
,
47 * The initial credentials for the initial task
49 struct cred init_cred
= {
50 .usage
= ATOMIC_INIT(4),
51 #ifdef CONFIG_DEBUG_CREDENTIALS
52 .subscribers
= ATOMIC_INIT(2),
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
,
61 .group_info
= &init_groups
,
63 .tgcred
= &init_tgcred
,
67 static inline void set_cred_subscribers(struct cred
*cred
, int n
)
69 #ifdef CONFIG_DEBUG_CREDENTIALS
70 atomic_set(&cred
->subscribers
, n
);
74 static inline int read_cred_subscribers(const struct cred
*cred
)
76 #ifdef CONFIG_DEBUG_CREDENTIALS
77 return atomic_read(&cred
->subscribers
);
83 static inline void alter_cred_subscribers(const struct cred
*_cred
, int n
)
85 #ifdef CONFIG_DEBUG_CREDENTIALS
86 struct cred
*cred
= (struct cred
*) _cred
;
88 atomic_add(n
, &cred
->subscribers
);
93 * Dispose of the shared task group credentials
96 static void release_tgcred_rcu(struct rcu_head
*rcu
)
98 struct thread_group_cred
*tgcred
=
99 container_of(rcu
, struct thread_group_cred
, rcu
);
101 BUG_ON(atomic_read(&tgcred
->usage
) != 0);
103 key_put(tgcred
->session_keyring
);
104 key_put(tgcred
->process_keyring
);
110 * Release a set of thread group credentials.
112 static void release_tgcred(struct cred
*cred
)
115 struct thread_group_cred
*tgcred
= cred
->tgcred
;
117 if (atomic_dec_and_test(&tgcred
->usage
))
118 call_rcu(&tgcred
->rcu
, release_tgcred_rcu
);
123 * The RCU callback to actually dispose of a set of credentials
125 static void put_cred_rcu(struct rcu_head
*rcu
)
127 struct cred
*cred
= container_of(rcu
, struct cred
, rcu
);
129 kdebug("put_cred_rcu(%p)", cred
);
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
));
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
));
146 security_cred_free(cred
);
147 key_put(cred
->thread_keyring
);
148 key_put(cred
->request_key_auth
);
149 release_tgcred(cred
);
150 put_group_info(cred
->group_info
);
151 free_uid(cred
->user
);
152 kmem_cache_free(cred_jar
, cred
);
156 * __put_cred - Destroy a set of credentials
157 * @cred: The record to release
159 * Destroy a set of credentials on which no references remain.
161 void __put_cred(struct cred
*cred
)
163 kdebug("__put_cred(%p{%d,%d})", cred
,
164 atomic_read(&cred
->usage
),
165 read_cred_subscribers(cred
));
167 BUG_ON(atomic_read(&cred
->usage
) != 0);
168 #ifdef CONFIG_DEBUG_CREDENTIALS
169 BUG_ON(read_cred_subscribers(cred
) != 0);
170 cred
->magic
= CRED_MAGIC_DEAD
;
171 cred
->put_addr
= __builtin_return_address(0);
173 BUG_ON(cred
== current
->cred
);
174 BUG_ON(cred
== current
->real_cred
);
176 call_rcu(&cred
->rcu
, put_cred_rcu
);
178 EXPORT_SYMBOL(__put_cred
);
181 * Clean up a task's credentials when it exits
183 void exit_creds(struct task_struct
*tsk
)
187 kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk
->pid
, tsk
->real_cred
, tsk
->cred
,
188 atomic_read(&tsk
->cred
->usage
),
189 read_cred_subscribers(tsk
->cred
));
191 cred
= (struct cred
*) tsk
->real_cred
;
192 tsk
->real_cred
= NULL
;
193 validate_creds(cred
);
194 alter_cred_subscribers(cred
, -1);
197 cred
= (struct cred
*) tsk
->cred
;
199 validate_creds(cred
);
200 alter_cred_subscribers(cred
, -1);
205 * prepare_creds - Prepare a new set of credentials for modification
207 * Prepare a new set of task credentials for modification. A task's creds
208 * shouldn't generally be modified directly, therefore this function is used to
209 * prepare a new copy, which the caller then modifies and then commits by
210 * calling commit_creds().
212 * Preparation involves making a copy of the objective creds for modification.
214 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
216 * Call commit_creds() or abort_creds() to clean up.
218 struct cred
*prepare_creds(void)
220 struct task_struct
*task
= current
;
221 const struct cred
*old
;
224 validate_process_creds();
226 new = kmem_cache_alloc(cred_jar
, GFP_KERNEL
);
230 kdebug("prepare_creds() alloc %p", new);
233 memcpy(new, old
, sizeof(struct cred
));
235 atomic_set(&new->usage
, 1);
236 set_cred_subscribers(new, 0);
237 get_group_info(new->group_info
);
241 key_get(new->thread_keyring
);
242 key_get(new->request_key_auth
);
243 atomic_inc(&new->tgcred
->usage
);
246 #ifdef CONFIG_SECURITY
247 new->security
= NULL
;
250 if (security_prepare_creds(new, old
, GFP_KERNEL
) < 0)
259 EXPORT_SYMBOL(prepare_creds
);
262 * Prepare credentials for current to perform an execve()
263 * - The caller must hold current->cred_guard_mutex
265 struct cred
*prepare_exec_creds(void)
267 struct thread_group_cred
*tgcred
= NULL
;
271 tgcred
= kmalloc(sizeof(*tgcred
), GFP_KERNEL
);
276 new = prepare_creds();
283 /* newly exec'd tasks don't get a thread keyring */
284 key_put(new->thread_keyring
);
285 new->thread_keyring
= NULL
;
287 /* create a new per-thread-group creds for all this set of threads to
289 memcpy(tgcred
, new->tgcred
, sizeof(struct thread_group_cred
));
291 atomic_set(&tgcred
->usage
, 1);
292 spin_lock_init(&tgcred
->lock
);
294 /* inherit the session keyring; new process keyring */
295 key_get(tgcred
->session_keyring
);
296 tgcred
->process_keyring
= NULL
;
299 new->tgcred
= tgcred
;
306 * prepare new credentials for the usermode helper dispatcher
308 struct cred
*prepare_usermodehelper_creds(void)
311 struct thread_group_cred
*tgcred
= NULL
;
316 tgcred
= kzalloc(sizeof(*new->tgcred
), GFP_ATOMIC
);
321 new = kmem_cache_alloc(cred_jar
, GFP_ATOMIC
);
325 kdebug("prepare_usermodehelper_creds() alloc %p", new);
327 memcpy(new, &init_cred
, sizeof(struct cred
));
329 atomic_set(&new->usage
, 1);
330 set_cred_subscribers(new, 0);
331 get_group_info(new->group_info
);
335 new->thread_keyring
= NULL
;
336 new->request_key_auth
= NULL
;
337 new->jit_keyring
= KEY_REQKEY_DEFL_DEFAULT
;
339 atomic_set(&tgcred
->usage
, 1);
340 spin_lock_init(&tgcred
->lock
);
341 new->tgcred
= tgcred
;
344 #ifdef CONFIG_SECURITY
345 new->security
= NULL
;
347 if (security_prepare_creds(new, &init_cred
, GFP_ATOMIC
) < 0)
351 BUG_ON(atomic_read(&new->usage
) != 1);
360 * Copy credentials for the new process created by fork()
362 * We share if we can, but under some circumstances we have to generate a new
365 * The new process gets the current process's subjective credentials as its
366 * objective and subjective credentials
368 int copy_creds(struct task_struct
*p
, unsigned long clone_flags
)
371 struct thread_group_cred
*tgcred
;
376 mutex_init(&p
->cred_guard_mutex
);
380 !p
->cred
->thread_keyring
&&
382 clone_flags
& CLONE_THREAD
384 p
->real_cred
= get_cred(p
->cred
);
386 alter_cred_subscribers(p
->cred
, 2);
387 kdebug("share_creds(%p{%d,%d})",
388 p
->cred
, atomic_read(&p
->cred
->usage
),
389 read_cred_subscribers(p
->cred
));
390 atomic_inc(&p
->cred
->user
->processes
);
394 new = prepare_creds();
398 if (clone_flags
& CLONE_NEWUSER
) {
399 ret
= create_user_ns(new);
405 /* new threads get their own thread keyrings if their parent already
407 if (new->thread_keyring
) {
408 key_put(new->thread_keyring
);
409 new->thread_keyring
= NULL
;
410 if (clone_flags
& CLONE_THREAD
)
411 install_thread_keyring_to_cred(new);
414 /* we share the process and session keyrings between all the threads in
415 * a process - this is slightly icky as we violate COW credentials a
417 if (!(clone_flags
& CLONE_THREAD
)) {
418 tgcred
= kmalloc(sizeof(*tgcred
), GFP_KERNEL
);
423 atomic_set(&tgcred
->usage
, 1);
424 spin_lock_init(&tgcred
->lock
);
425 tgcred
->process_keyring
= NULL
;
426 tgcred
->session_keyring
= key_get(new->tgcred
->session_keyring
);
429 new->tgcred
= tgcred
;
433 atomic_inc(&new->user
->processes
);
434 p
->cred
= p
->real_cred
= get_cred(new);
435 alter_cred_subscribers(new, 2);
445 * commit_creds - Install new credentials upon the current task
446 * @new: The credentials to be assigned
448 * Install a new set of credentials to the current task, using RCU to replace
449 * the old set. Both the objective and the subjective credentials pointers are
450 * updated. This function may not be called if the subjective credentials are
451 * in an overridden state.
453 * This function eats the caller's reference to the new credentials.
455 * Always returns 0 thus allowing this function to be tail-called at the end
456 * of, say, sys_setgid().
458 int commit_creds(struct cred
*new)
460 struct task_struct
*task
= current
;
461 const struct cred
*old
= task
->real_cred
;
463 kdebug("commit_creds(%p{%d,%d})", new,
464 atomic_read(&new->usage
),
465 read_cred_subscribers(new));
467 BUG_ON(task
->cred
!= old
);
468 #ifdef CONFIG_DEBUG_CREDENTIALS
469 BUG_ON(read_cred_subscribers(old
) < 2);
473 BUG_ON(atomic_read(&new->usage
) < 1);
475 security_commit_creds(new, old
);
477 get_cred(new); /* we will require a ref for the subj creds too */
479 /* dumpability changes */
480 if (old
->euid
!= new->euid
||
481 old
->egid
!= new->egid
||
482 old
->fsuid
!= new->fsuid
||
483 old
->fsgid
!= new->fsgid
||
484 !cap_issubset(new->cap_permitted
, old
->cap_permitted
)) {
486 set_dumpable(task
->mm
, suid_dumpable
);
487 task
->pdeath_signal
= 0;
491 /* alter the thread keyring */
492 if (new->fsuid
!= old
->fsuid
)
493 key_fsuid_changed(task
);
494 if (new->fsgid
!= old
->fsgid
)
495 key_fsgid_changed(task
);
498 * - What if a process setreuid()'s and this brings the
499 * new uid over his NPROC rlimit? We can check this now
500 * cheaply with the new uid cache, so if it matters
501 * we should be checking for it. -DaveM
503 alter_cred_subscribers(new, 2);
504 if (new->user
!= old
->user
)
505 atomic_inc(&new->user
->processes
);
506 rcu_assign_pointer(task
->real_cred
, new);
507 rcu_assign_pointer(task
->cred
, new);
508 if (new->user
!= old
->user
)
509 atomic_dec(&old
->user
->processes
);
510 alter_cred_subscribers(old
, -2);
512 sched_switch_user(task
);
514 /* send notifications */
515 if (new->uid
!= old
->uid
||
516 new->euid
!= old
->euid
||
517 new->suid
!= old
->suid
||
518 new->fsuid
!= old
->fsuid
)
519 proc_id_connector(task
, PROC_EVENT_UID
);
521 if (new->gid
!= old
->gid
||
522 new->egid
!= old
->egid
||
523 new->sgid
!= old
->sgid
||
524 new->fsgid
!= old
->fsgid
)
525 proc_id_connector(task
, PROC_EVENT_GID
);
527 /* release the old obj and subj refs both */
532 EXPORT_SYMBOL(commit_creds
);
535 * abort_creds - Discard a set of credentials and unlock the current task
536 * @new: The credentials that were going to be applied
538 * Discard a set of credentials that were under construction and unlock the
541 void abort_creds(struct cred
*new)
543 kdebug("abort_creds(%p{%d,%d})", new,
544 atomic_read(&new->usage
),
545 read_cred_subscribers(new));
547 #ifdef CONFIG_DEBUG_CREDENTIALS
548 BUG_ON(read_cred_subscribers(new) != 0);
550 BUG_ON(atomic_read(&new->usage
) < 1);
553 EXPORT_SYMBOL(abort_creds
);
556 * override_creds - Override the current process's subjective credentials
557 * @new: The credentials to be assigned
559 * Install a set of temporary override subjective credentials on the current
560 * process, returning the old set for later reversion.
562 const struct cred
*override_creds(const struct cred
*new)
564 const struct cred
*old
= current
->cred
;
566 kdebug("override_creds(%p{%d,%d})", new,
567 atomic_read(&new->usage
),
568 read_cred_subscribers(new));
573 alter_cred_subscribers(new, 1);
574 rcu_assign_pointer(current
->cred
, new);
575 alter_cred_subscribers(old
, -1);
577 kdebug("override_creds() = %p{%d,%d}", old
,
578 atomic_read(&old
->usage
),
579 read_cred_subscribers(old
));
582 EXPORT_SYMBOL(override_creds
);
585 * revert_creds - Revert a temporary subjective credentials override
586 * @old: The credentials to be restored
588 * Revert a temporary set of override subjective credentials to an old set,
589 * discarding the override set.
591 void revert_creds(const struct cred
*old
)
593 const struct cred
*override
= current
->cred
;
595 kdebug("revert_creds(%p{%d,%d})", old
,
596 atomic_read(&old
->usage
),
597 read_cred_subscribers(old
));
600 validate_creds(override
);
601 alter_cred_subscribers(old
, 1);
602 rcu_assign_pointer(current
->cred
, old
);
603 alter_cred_subscribers(override
, -1);
606 EXPORT_SYMBOL(revert_creds
);
609 * initialise the credentials stuff
611 void __init
cred_init(void)
613 /* allocate a slab in which we can store credentials */
614 cred_jar
= kmem_cache_create("cred_jar", sizeof(struct cred
),
615 0, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
619 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
620 * @daemon: A userspace daemon to be used as a reference
622 * Prepare a set of credentials for a kernel service. This can then be used to
623 * override a task's own credentials so that work can be done on behalf of that
624 * task that requires a different subjective context.
626 * @daemon is used to provide a base for the security record, but can be NULL.
627 * If @daemon is supplied, then the security data will be derived from that;
628 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
630 * The caller may change these controls afterwards if desired.
632 * Returns the new credentials or NULL if out of memory.
634 * Does not take, and does not return holding current->cred_replace_mutex.
636 struct cred
*prepare_kernel_cred(struct task_struct
*daemon
)
638 const struct cred
*old
;
641 new = kmem_cache_alloc(cred_jar
, GFP_KERNEL
);
645 kdebug("prepare_kernel_cred() alloc %p", new);
648 old
= get_task_cred(daemon
);
650 old
= get_cred(&init_cred
);
656 get_group_info(new->group_info
);
659 atomic_inc(&init_tgcred
.usage
);
660 new->tgcred
= &init_tgcred
;
661 new->request_key_auth
= NULL
;
662 new->thread_keyring
= NULL
;
663 new->jit_keyring
= KEY_REQKEY_DEFL_THREAD_KEYRING
;
666 #ifdef CONFIG_SECURITY
667 new->security
= NULL
;
669 if (security_prepare_creds(new, old
, GFP_KERNEL
) < 0)
672 atomic_set(&new->usage
, 1);
673 set_cred_subscribers(new, 0);
683 EXPORT_SYMBOL(prepare_kernel_cred
);
686 * set_security_override - Set the security ID in a set of credentials
687 * @new: The credentials to alter
688 * @secid: The LSM security ID to set
690 * Set the LSM security ID in a set of credentials so that the subjective
691 * security is overridden when an alternative set of credentials is used.
693 int set_security_override(struct cred
*new, u32 secid
)
695 return security_kernel_act_as(new, secid
);
697 EXPORT_SYMBOL(set_security_override
);
700 * set_security_override_from_ctx - Set the security ID in a set of credentials
701 * @new: The credentials to alter
702 * @secctx: The LSM security context to generate the security ID from.
704 * Set the LSM security ID in a set of credentials so that the subjective
705 * security is overridden when an alternative set of credentials is used. The
706 * security ID is specified in string form as a security context to be
707 * interpreted by the LSM.
709 int set_security_override_from_ctx(struct cred
*new, const char *secctx
)
714 ret
= security_secctx_to_secid(secctx
, strlen(secctx
), &secid
);
718 return set_security_override(new, secid
);
720 EXPORT_SYMBOL(set_security_override_from_ctx
);
723 * set_create_files_as - Set the LSM file create context in a set of credentials
724 * @new: The credentials to alter
725 * @inode: The inode to take the context from
727 * Change the LSM file creation context in a set of credentials to be the same
728 * as the object context of the specified inode, so that the new inodes have
729 * the same MAC context as that inode.
731 int set_create_files_as(struct cred
*new, struct inode
*inode
)
733 new->fsuid
= inode
->i_uid
;
734 new->fsgid
= inode
->i_gid
;
735 return security_kernel_create_files_as(new, inode
);
737 EXPORT_SYMBOL(set_create_files_as
);
739 #ifdef CONFIG_DEBUG_CREDENTIALS
742 * dump invalid credentials
744 static void dump_invalid_creds(const struct cred
*cred
, const char *label
,
745 const struct task_struct
*tsk
)
747 printk(KERN_ERR
"CRED: %s credentials: %p %s%s%s\n",
749 cred
== &init_cred
? "[init]" : "",
750 cred
== tsk
->real_cred
? "[real]" : "",
751 cred
== tsk
->cred
? "[eff]" : "");
752 printk(KERN_ERR
"CRED: ->magic=%x, put_addr=%p\n",
753 cred
->magic
, cred
->put_addr
);
754 printk(KERN_ERR
"CRED: ->usage=%d, subscr=%d\n",
755 atomic_read(&cred
->usage
),
756 read_cred_subscribers(cred
));
757 printk(KERN_ERR
"CRED: ->*uid = { %d,%d,%d,%d }\n",
758 cred
->uid
, cred
->euid
, cred
->suid
, cred
->fsuid
);
759 printk(KERN_ERR
"CRED: ->*gid = { %d,%d,%d,%d }\n",
760 cred
->gid
, cred
->egid
, cred
->sgid
, cred
->fsgid
);
761 #ifdef CONFIG_SECURITY
762 printk(KERN_ERR
"CRED: ->security is %p\n", cred
->security
);
763 if ((unsigned long) cred
->security
>= PAGE_SIZE
&&
764 (((unsigned long) cred
->security
& 0xffffff00) !=
765 (POISON_FREE
<< 24 | POISON_FREE
<< 16 | POISON_FREE
<< 8)))
766 printk(KERN_ERR
"CRED: ->security {%x, %x}\n",
767 ((u32
*)cred
->security
)[0],
768 ((u32
*)cred
->security
)[1]);
773 * report use of invalid credentials
775 void __invalid_creds(const struct cred
*cred
, const char *file
, unsigned line
)
777 printk(KERN_ERR
"CRED: Invalid credentials\n");
778 printk(KERN_ERR
"CRED: At %s:%u\n", file
, line
);
779 dump_invalid_creds(cred
, "Specified", current
);
782 EXPORT_SYMBOL(__invalid_creds
);
785 * check the credentials on a process
787 void __validate_process_creds(struct task_struct
*tsk
,
788 const char *file
, unsigned line
)
790 if (tsk
->cred
== tsk
->real_cred
) {
791 if (unlikely(read_cred_subscribers(tsk
->cred
) < 2 ||
792 creds_are_invalid(tsk
->cred
)))
795 if (unlikely(read_cred_subscribers(tsk
->real_cred
) < 1 ||
796 read_cred_subscribers(tsk
->cred
) < 1 ||
797 creds_are_invalid(tsk
->real_cred
) ||
798 creds_are_invalid(tsk
->cred
)))
804 printk(KERN_ERR
"CRED: Invalid process credentials\n");
805 printk(KERN_ERR
"CRED: At %s:%u\n", file
, line
);
807 dump_invalid_creds(tsk
->real_cred
, "Real", tsk
);
808 if (tsk
->cred
!= tsk
->real_cred
)
809 dump_invalid_creds(tsk
->cred
, "Effective", tsk
);
811 printk(KERN_ERR
"CRED: Effective creds == Real creds\n");
814 EXPORT_SYMBOL(__validate_process_creds
);
817 * check creds for do_exit()
819 void validate_creds_for_do_exit(struct task_struct
*tsk
)
821 kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
822 tsk
->real_cred
, tsk
->cred
,
823 atomic_read(&tsk
->cred
->usage
),
824 read_cred_subscribers(tsk
->cred
));
826 __validate_process_creds(tsk
, __FILE__
, __LINE__
);
829 #endif /* CONFIG_DEBUG_CREDENTIALS */