ACPI: thinkpad-acpi: preserve radio state across shutdown
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / cred.c
blob3a039189d70748b294082301d9636d467c019c3b
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"
21 static struct kmem_cache *cred_jar;
24 * The common credentials for the initial task's thread group
26 #ifdef CONFIG_KEYS
27 static struct thread_group_cred init_tgcred = {
28 .usage = ATOMIC_INIT(2),
29 .tgid = 0,
30 .lock = SPIN_LOCK_UNLOCKED,
32 #endif
35 * The initial credentials for the initial task
37 struct cred init_cred = {
38 .usage = ATOMIC_INIT(4),
39 .securebits = SECUREBITS_DEFAULT,
40 .cap_inheritable = CAP_INIT_INH_SET,
41 .cap_permitted = CAP_FULL_SET,
42 .cap_effective = CAP_INIT_EFF_SET,
43 .cap_bset = CAP_INIT_BSET,
44 .user = INIT_USER,
45 .group_info = &init_groups,
46 #ifdef CONFIG_KEYS
47 .tgcred = &init_tgcred,
48 #endif
52 * Dispose of the shared task group credentials
54 #ifdef CONFIG_KEYS
55 static void release_tgcred_rcu(struct rcu_head *rcu)
57 struct thread_group_cred *tgcred =
58 container_of(rcu, struct thread_group_cred, rcu);
60 BUG_ON(atomic_read(&tgcred->usage) != 0);
62 key_put(tgcred->session_keyring);
63 key_put(tgcred->process_keyring);
64 kfree(tgcred);
66 #endif
69 * Release a set of thread group credentials.
71 static void release_tgcred(struct cred *cred)
73 #ifdef CONFIG_KEYS
74 struct thread_group_cred *tgcred = cred->tgcred;
76 if (atomic_dec_and_test(&tgcred->usage))
77 call_rcu(&tgcred->rcu, release_tgcred_rcu);
78 #endif
82 * The RCU callback to actually dispose of a set of credentials
84 static void put_cred_rcu(struct rcu_head *rcu)
86 struct cred *cred = container_of(rcu, struct cred, rcu);
88 if (atomic_read(&cred->usage) != 0)
89 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
90 cred, atomic_read(&cred->usage));
92 security_cred_free(cred);
93 key_put(cred->thread_keyring);
94 key_put(cred->request_key_auth);
95 release_tgcred(cred);
96 put_group_info(cred->group_info);
97 free_uid(cred->user);
98 kmem_cache_free(cred_jar, cred);
102 * __put_cred - Destroy a set of credentials
103 * @cred: The record to release
105 * Destroy a set of credentials on which no references remain.
107 void __put_cred(struct cred *cred)
109 BUG_ON(atomic_read(&cred->usage) != 0);
111 call_rcu(&cred->rcu, put_cred_rcu);
113 EXPORT_SYMBOL(__put_cred);
116 * prepare_creds - Prepare a new set of credentials for modification
118 * Prepare a new set of task credentials for modification. A task's creds
119 * shouldn't generally be modified directly, therefore this function is used to
120 * prepare a new copy, which the caller then modifies and then commits by
121 * calling commit_creds().
123 * Preparation involves making a copy of the objective creds for modification.
125 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
127 * Call commit_creds() or abort_creds() to clean up.
129 struct cred *prepare_creds(void)
131 struct task_struct *task = current;
132 const struct cred *old;
133 struct cred *new;
135 BUG_ON(atomic_read(&task->real_cred->usage) < 1);
137 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
138 if (!new)
139 return NULL;
141 old = task->cred;
142 memcpy(new, old, sizeof(struct cred));
144 atomic_set(&new->usage, 1);
145 get_group_info(new->group_info);
146 get_uid(new->user);
148 #ifdef CONFIG_KEYS
149 key_get(new->thread_keyring);
150 key_get(new->request_key_auth);
151 atomic_inc(&new->tgcred->usage);
152 #endif
154 #ifdef CONFIG_SECURITY
155 new->security = NULL;
156 #endif
158 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
159 goto error;
160 return new;
162 error:
163 abort_creds(new);
164 return NULL;
166 EXPORT_SYMBOL(prepare_creds);
169 * Prepare credentials for current to perform an execve()
170 * - The caller must hold current->cred_exec_mutex
172 struct cred *prepare_exec_creds(void)
174 struct thread_group_cred *tgcred = NULL;
175 struct cred *new;
177 #ifdef CONFIG_KEYS
178 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
179 if (!tgcred)
180 return NULL;
181 #endif
183 new = prepare_creds();
184 if (!new) {
185 kfree(tgcred);
186 return new;
189 #ifdef CONFIG_KEYS
190 /* newly exec'd tasks don't get a thread keyring */
191 key_put(new->thread_keyring);
192 new->thread_keyring = NULL;
194 /* create a new per-thread-group creds for all this set of threads to
195 * share */
196 memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
198 atomic_set(&tgcred->usage, 1);
199 spin_lock_init(&tgcred->lock);
201 /* inherit the session keyring; new process keyring */
202 key_get(tgcred->session_keyring);
203 tgcred->process_keyring = NULL;
205 release_tgcred(new);
206 new->tgcred = tgcred;
207 #endif
209 return new;
213 * prepare new credentials for the usermode helper dispatcher
215 struct cred *prepare_usermodehelper_creds(void)
217 #ifdef CONFIG_KEYS
218 struct thread_group_cred *tgcred = NULL;
219 #endif
220 struct cred *new;
222 #ifdef CONFIG_KEYS
223 tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
224 if (!tgcred)
225 return NULL;
226 #endif
228 new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
229 if (!new)
230 return NULL;
232 memcpy(new, &init_cred, sizeof(struct cred));
234 atomic_set(&new->usage, 1);
235 get_group_info(new->group_info);
236 get_uid(new->user);
238 #ifdef CONFIG_KEYS
239 new->thread_keyring = NULL;
240 new->request_key_auth = NULL;
241 new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
243 atomic_set(&tgcred->usage, 1);
244 spin_lock_init(&tgcred->lock);
245 new->tgcred = tgcred;
246 #endif
248 #ifdef CONFIG_SECURITY
249 new->security = NULL;
250 #endif
251 if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
252 goto error;
254 BUG_ON(atomic_read(&new->usage) != 1);
255 return new;
257 error:
258 put_cred(new);
259 return NULL;
263 * Copy credentials for the new process created by fork()
265 * We share if we can, but under some circumstances we have to generate a new
266 * set.
268 * The new process gets the current process's subjective credentials as its
269 * objective and subjective credentials
271 int copy_creds(struct task_struct *p, unsigned long clone_flags)
273 #ifdef CONFIG_KEYS
274 struct thread_group_cred *tgcred;
275 #endif
276 struct cred *new;
277 int ret;
279 mutex_init(&p->cred_exec_mutex);
281 if (
282 #ifdef CONFIG_KEYS
283 !p->cred->thread_keyring &&
284 #endif
285 clone_flags & CLONE_THREAD
287 p->real_cred = get_cred(p->cred);
288 get_cred(p->cred);
289 atomic_inc(&p->cred->user->processes);
290 return 0;
293 new = prepare_creds();
294 if (!new)
295 return -ENOMEM;
297 if (clone_flags & CLONE_NEWUSER) {
298 ret = create_user_ns(new);
299 if (ret < 0)
300 goto error_put;
303 #ifdef CONFIG_KEYS
304 /* new threads get their own thread keyrings if their parent already
305 * had one */
306 if (new->thread_keyring) {
307 key_put(new->thread_keyring);
308 new->thread_keyring = NULL;
309 if (clone_flags & CLONE_THREAD)
310 install_thread_keyring_to_cred(new);
313 /* we share the process and session keyrings between all the threads in
314 * a process - this is slightly icky as we violate COW credentials a
315 * bit */
316 if (!(clone_flags & CLONE_THREAD)) {
317 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
318 if (!tgcred) {
319 ret = -ENOMEM;
320 goto error_put;
322 atomic_set(&tgcred->usage, 1);
323 spin_lock_init(&tgcred->lock);
324 tgcred->process_keyring = NULL;
325 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
327 release_tgcred(new);
328 new->tgcred = tgcred;
330 #endif
332 atomic_inc(&new->user->processes);
333 p->cred = p->real_cred = get_cred(new);
334 return 0;
336 error_put:
337 put_cred(new);
338 return ret;
342 * commit_creds - Install new credentials upon the current task
343 * @new: The credentials to be assigned
345 * Install a new set of credentials to the current task, using RCU to replace
346 * the old set. Both the objective and the subjective credentials pointers are
347 * updated. This function may not be called if the subjective credentials are
348 * in an overridden state.
350 * This function eats the caller's reference to the new credentials.
352 * Always returns 0 thus allowing this function to be tail-called at the end
353 * of, say, sys_setgid().
355 int commit_creds(struct cred *new)
357 struct task_struct *task = current;
358 const struct cred *old;
360 BUG_ON(task->cred != task->real_cred);
361 BUG_ON(atomic_read(&task->real_cred->usage) < 2);
362 BUG_ON(atomic_read(&new->usage) < 1);
364 old = task->real_cred;
365 security_commit_creds(new, old);
367 get_cred(new); /* we will require a ref for the subj creds too */
369 /* dumpability changes */
370 if (old->euid != new->euid ||
371 old->egid != new->egid ||
372 old->fsuid != new->fsuid ||
373 old->fsgid != new->fsgid ||
374 !cap_issubset(new->cap_permitted, old->cap_permitted)) {
375 if (task->mm)
376 set_dumpable(task->mm, suid_dumpable);
377 task->pdeath_signal = 0;
378 smp_wmb();
381 /* alter the thread keyring */
382 if (new->fsuid != old->fsuid)
383 key_fsuid_changed(task);
384 if (new->fsgid != old->fsgid)
385 key_fsgid_changed(task);
387 /* do it
388 * - What if a process setreuid()'s and this brings the
389 * new uid over his NPROC rlimit? We can check this now
390 * cheaply with the new uid cache, so if it matters
391 * we should be checking for it. -DaveM
393 if (new->user != old->user)
394 atomic_inc(&new->user->processes);
395 rcu_assign_pointer(task->real_cred, new);
396 rcu_assign_pointer(task->cred, new);
397 if (new->user != old->user)
398 atomic_dec(&old->user->processes);
400 sched_switch_user(task);
402 /* send notifications */
403 if (new->uid != old->uid ||
404 new->euid != old->euid ||
405 new->suid != old->suid ||
406 new->fsuid != old->fsuid)
407 proc_id_connector(task, PROC_EVENT_UID);
409 if (new->gid != old->gid ||
410 new->egid != old->egid ||
411 new->sgid != old->sgid ||
412 new->fsgid != old->fsgid)
413 proc_id_connector(task, PROC_EVENT_GID);
415 /* release the old obj and subj refs both */
416 put_cred(old);
417 put_cred(old);
418 return 0;
420 EXPORT_SYMBOL(commit_creds);
423 * abort_creds - Discard a set of credentials and unlock the current task
424 * @new: The credentials that were going to be applied
426 * Discard a set of credentials that were under construction and unlock the
427 * current task.
429 void abort_creds(struct cred *new)
431 BUG_ON(atomic_read(&new->usage) < 1);
432 put_cred(new);
434 EXPORT_SYMBOL(abort_creds);
437 * override_creds - Override the current process's subjective credentials
438 * @new: The credentials to be assigned
440 * Install a set of temporary override subjective credentials on the current
441 * process, returning the old set for later reversion.
443 const struct cred *override_creds(const struct cred *new)
445 const struct cred *old = current->cred;
447 rcu_assign_pointer(current->cred, get_cred(new));
448 return old;
450 EXPORT_SYMBOL(override_creds);
453 * revert_creds - Revert a temporary subjective credentials override
454 * @old: The credentials to be restored
456 * Revert a temporary set of override subjective credentials to an old set,
457 * discarding the override set.
459 void revert_creds(const struct cred *old)
461 const struct cred *override = current->cred;
463 rcu_assign_pointer(current->cred, old);
464 put_cred(override);
466 EXPORT_SYMBOL(revert_creds);
469 * initialise the credentials stuff
471 void __init cred_init(void)
473 /* allocate a slab in which we can store credentials */
474 cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
475 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
479 * prepare_kernel_cred - Prepare a set of credentials for a kernel service
480 * @daemon: A userspace daemon to be used as a reference
482 * Prepare a set of credentials for a kernel service. This can then be used to
483 * override a task's own credentials so that work can be done on behalf of that
484 * task that requires a different subjective context.
486 * @daemon is used to provide a base for the security record, but can be NULL.
487 * If @daemon is supplied, then the security data will be derived from that;
488 * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
490 * The caller may change these controls afterwards if desired.
492 * Returns the new credentials or NULL if out of memory.
494 * Does not take, and does not return holding current->cred_replace_mutex.
496 struct cred *prepare_kernel_cred(struct task_struct *daemon)
498 const struct cred *old;
499 struct cred *new;
501 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
502 if (!new)
503 return NULL;
505 if (daemon)
506 old = get_task_cred(daemon);
507 else
508 old = get_cred(&init_cred);
510 *new = *old;
511 get_uid(new->user);
512 get_group_info(new->group_info);
514 #ifdef CONFIG_KEYS
515 atomic_inc(&init_tgcred.usage);
516 new->tgcred = &init_tgcred;
517 new->request_key_auth = NULL;
518 new->thread_keyring = NULL;
519 new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
520 #endif
522 #ifdef CONFIG_SECURITY
523 new->security = NULL;
524 #endif
525 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
526 goto error;
528 atomic_set(&new->usage, 1);
529 put_cred(old);
530 return new;
532 error:
533 put_cred(new);
534 put_cred(old);
535 return NULL;
537 EXPORT_SYMBOL(prepare_kernel_cred);
540 * set_security_override - Set the security ID in a set of credentials
541 * @new: The credentials to alter
542 * @secid: The LSM security ID to set
544 * Set the LSM security ID in a set of credentials so that the subjective
545 * security is overridden when an alternative set of credentials is used.
547 int set_security_override(struct cred *new, u32 secid)
549 return security_kernel_act_as(new, secid);
551 EXPORT_SYMBOL(set_security_override);
554 * set_security_override_from_ctx - Set the security ID in a set of credentials
555 * @new: The credentials to alter
556 * @secctx: The LSM security context to generate the security ID from.
558 * Set the LSM security ID in a set of credentials so that the subjective
559 * security is overridden when an alternative set of credentials is used. The
560 * security ID is specified in string form as a security context to be
561 * interpreted by the LSM.
563 int set_security_override_from_ctx(struct cred *new, const char *secctx)
565 u32 secid;
566 int ret;
568 ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
569 if (ret < 0)
570 return ret;
572 return set_security_override(new, secid);
574 EXPORT_SYMBOL(set_security_override_from_ctx);
577 * set_create_files_as - Set the LSM file create context in a set of credentials
578 * @new: The credentials to alter
579 * @inode: The inode to take the context from
581 * Change the LSM file creation context in a set of credentials to be the same
582 * as the object context of the specified inode, so that the new inodes have
583 * the same MAC context as that inode.
585 int set_create_files_as(struct cred *new, struct inode *inode)
587 new->fsuid = inode->i_uid;
588 new->fsgid = inode->i_gid;
589 return security_kernel_create_files_as(new, inode);
591 EXPORT_SYMBOL(set_create_files_as);