1 /* Task credentials management
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
27 static struct thread_group_cred init_tgcred = {
28 .usage = ATOMIC_INIT(2),
30 .lock = SPIN_LOCK_UNLOCKED,
35 * The initial credentials for the initial task
37 struct cred init_cred = {
38 .usage = ATOMIC_INIT(3),
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,
45 .group_info = &init_groups,
47 .tgcred = &init_tgcred,
52 * Dispose of the shared task group credentials
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);
69 * Release a set of thread group credentials.
71 void release_tgcred(struct cred *cred)
74 struct thread_group_cred *tgcred = cred->tgcred;
76 if (atomic_dec_and_test(&tgcred->usage))
77 call_rcu(&tgcred->rcu, release_tgcred_rcu);
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);
96 put_group_info(cred->group_info);
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 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
125 * Call commit_creds() or abort_creds() to clean up.
127 struct cred *prepare_creds(void)
129 struct task_struct *task = current;
130 const struct cred *old;
133 BUG_ON(atomic_read(&task->cred->usage) < 1);
135 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
140 memcpy(new, old, sizeof(struct cred));
142 atomic_set(&new->usage, 1);
143 get_group_info(new->group_info);
147 key_get(new->thread_keyring);
148 key_get(new->request_key_auth);
149 atomic_inc(&new->tgcred->usage);
152 #ifdef CONFIG_SECURITY
153 new->security = NULL;
156 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
164 EXPORT_SYMBOL(prepare_creds);
167 * prepare new credentials for the usermode helper dispatcher
169 struct cred *prepare_usermodehelper_creds(void)
172 struct thread_group_cred *tgcred = NULL;
177 tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
182 new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
186 memcpy(new, &init_cred, sizeof(struct cred));
188 atomic_set(&new->usage, 1);
189 get_group_info(new->group_info);
193 new->thread_keyring = NULL;
194 new->request_key_auth = NULL;
195 new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
197 atomic_set(&tgcred->usage, 1);
198 spin_lock_init(&tgcred->lock);
199 new->tgcred = tgcred;
202 #ifdef CONFIG_SECURITY
203 new->security = NULL;
205 if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
208 BUG_ON(atomic_read(&new->usage) != 1);
217 * Copy credentials for the new process created by fork()
219 * We share if we can, but under some circumstances we have to generate a new
222 int copy_creds(struct task_struct *p, unsigned long clone_flags)
225 struct thread_group_cred *tgcred;
229 mutex_init(&p->cred_exec_mutex);
233 !p->cred->thread_keyring &&
235 clone_flags & CLONE_THREAD
238 atomic_inc(&p->cred->user->processes);
242 new = prepare_creds();
247 /* new threads get their own thread keyrings if their parent already
249 if (new->thread_keyring) {
250 key_put(new->thread_keyring);
251 new->thread_keyring = NULL;
252 if (clone_flags & CLONE_THREAD)
253 install_thread_keyring_to_cred(new);
256 /* we share the process and session keyrings between all the threads in
257 * a process - this is slightly icky as we violate COW credentials a
259 if (!(clone_flags & CLONE_THREAD)) {
260 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
265 atomic_set(&tgcred->usage, 1);
266 spin_lock_init(&tgcred->lock);
267 tgcred->process_keyring = NULL;
268 tgcred->session_keyring = key_get(new->tgcred->session_keyring);
271 new->tgcred = tgcred;
275 atomic_inc(&new->user->processes);
281 * commit_creds - Install new credentials upon the current task
282 * @new: The credentials to be assigned
284 * Install a new set of credentials to the current task, using RCU to replace
287 * This function eats the caller's reference to the new credentials.
289 * Always returns 0 thus allowing this function to be tail-called at the end
290 * of, say, sys_setgid().
292 int commit_creds(struct cred *new)
294 struct task_struct *task = current;
295 const struct cred *old;
297 BUG_ON(atomic_read(&new->usage) < 1);
298 BUG_ON(atomic_read(&task->cred->usage) < 1);
301 security_commit_creds(new, old);
303 /* dumpability changes */
304 if (old->euid != new->euid ||
305 old->egid != new->egid ||
306 old->fsuid != new->fsuid ||
307 old->fsgid != new->fsgid ||
308 !cap_issubset(new->cap_permitted, old->cap_permitted)) {
309 set_dumpable(task->mm, suid_dumpable);
310 task->pdeath_signal = 0;
314 /* alter the thread keyring */
315 if (new->fsuid != old->fsuid)
316 key_fsuid_changed(task);
317 if (new->fsgid != old->fsgid)
318 key_fsgid_changed(task);
321 * - What if a process setreuid()'s and this brings the
322 * new uid over his NPROC rlimit? We can check this now
323 * cheaply with the new uid cache, so if it matters
324 * we should be checking for it. -DaveM
326 if (new->user != old->user)
327 atomic_inc(&new->user->processes);
328 rcu_assign_pointer(task->cred, new);
329 if (new->user != old->user)
330 atomic_dec(&old->user->processes);
332 sched_switch_user(task);
334 /* send notifications */
335 if (new->uid != old->uid ||
336 new->euid != old->euid ||
337 new->suid != old->suid ||
338 new->fsuid != old->fsuid)
339 proc_id_connector(task, PROC_EVENT_UID);
341 if (new->gid != old->gid ||
342 new->egid != old->egid ||
343 new->sgid != old->sgid ||
344 new->fsgid != old->fsgid)
345 proc_id_connector(task, PROC_EVENT_GID);
350 EXPORT_SYMBOL(commit_creds);
353 * abort_creds - Discard a set of credentials and unlock the current task
354 * @new: The credentials that were going to be applied
356 * Discard a set of credentials that were under construction and unlock the
359 void abort_creds(struct cred *new)
361 BUG_ON(atomic_read(&new->usage) < 1);
364 EXPORT_SYMBOL(abort_creds);
367 * override_creds - Temporarily override the current process's credentials
368 * @new: The credentials to be assigned
370 * Install a set of temporary override credentials on the current process,
371 * returning the old set for later reversion.
373 const struct cred *override_creds(const struct cred *new)
375 const struct cred *old = current->cred;
377 rcu_assign_pointer(current->cred, get_cred(new));
380 EXPORT_SYMBOL(override_creds);
383 * revert_creds - Revert a temporary credentials override
384 * @old: The credentials to be restored
386 * Revert a temporary set of override credentials to an old set, discarding the
389 void revert_creds(const struct cred *old)
391 const struct cred *override = current->cred;
393 rcu_assign_pointer(current->cred, old);
396 EXPORT_SYMBOL(revert_creds);
399 * initialise the credentials stuff
401 void __init cred_init(void)
403 /* allocate a slab in which we can store credentials */
404 cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
405 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);