blob: cb6b5eda978df8d6a30866f1adbaae7382c4b8a8 [file] [log] [blame]
David Howellsf1752ee2008-11-14 10:39:17 +11001/* Task credentials management
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/sched.h>
14#include <linux/key.h>
15#include <linux/keyctl.h>
16#include <linux/init_task.h>
17#include <linux/security.h>
David Howellsd84f4f92008-11-14 10:39:23 +110018#include <linux/cn_proc.h>
19#include "cred-internals.h"
20
21static struct kmem_cache *cred_jar;
David Howellsf1752ee2008-11-14 10:39:17 +110022
23/*
David Howellsbb952bb2008-11-14 10:39:20 +110024 * The common credentials for the initial task's thread group
25 */
26#ifdef CONFIG_KEYS
27static struct thread_group_cred init_tgcred = {
28 .usage = ATOMIC_INIT(2),
29 .tgid = 0,
30 .lock = SPIN_LOCK_UNLOCKED,
31};
32#endif
33
34/*
David Howellsf1752ee2008-11-14 10:39:17 +110035 * The initial credentials for the initial task
36 */
37struct 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,
44 .user = INIT_USER,
45 .group_info = &init_groups,
David Howellsbb952bb2008-11-14 10:39:20 +110046#ifdef CONFIG_KEYS
47 .tgcred = &init_tgcred,
48#endif
David Howellsf1752ee2008-11-14 10:39:17 +110049};
50
51/*
David Howellsbb952bb2008-11-14 10:39:20 +110052 * Dispose of the shared task group credentials
53 */
54#ifdef CONFIG_KEYS
55static void release_tgcred_rcu(struct rcu_head *rcu)
56{
57 struct thread_group_cred *tgcred =
58 container_of(rcu, struct thread_group_cred, rcu);
59
60 BUG_ON(atomic_read(&tgcred->usage) != 0);
61
62 key_put(tgcred->session_keyring);
63 key_put(tgcred->process_keyring);
64 kfree(tgcred);
65}
66#endif
67
68/*
69 * Release a set of thread group credentials.
70 */
David Howellsd84f4f92008-11-14 10:39:23 +110071void release_tgcred(struct cred *cred)
David Howellsbb952bb2008-11-14 10:39:20 +110072{
73#ifdef CONFIG_KEYS
74 struct thread_group_cred *tgcred = cred->tgcred;
75
76 if (atomic_dec_and_test(&tgcred->usage))
77 call_rcu(&tgcred->rcu, release_tgcred_rcu);
78#endif
79}
80
81/*
David Howellsf1752ee2008-11-14 10:39:17 +110082 * The RCU callback to actually dispose of a set of credentials
83 */
84static void put_cred_rcu(struct rcu_head *rcu)
85{
86 struct cred *cred = container_of(rcu, struct cred, rcu);
87
David Howellsd84f4f92008-11-14 10:39:23 +110088 if (atomic_read(&cred->usage) != 0)
89 panic("CRED: put_cred_rcu() sees %p with usage %d\n",
90 cred, atomic_read(&cred->usage));
David Howellsf1752ee2008-11-14 10:39:17 +110091
David Howellsd84f4f92008-11-14 10:39:23 +110092 security_cred_free(cred);
David Howellsf1752ee2008-11-14 10:39:17 +110093 key_put(cred->thread_keyring);
94 key_put(cred->request_key_auth);
David Howellsbb952bb2008-11-14 10:39:20 +110095 release_tgcred(cred);
David Howellsf1752ee2008-11-14 10:39:17 +110096 put_group_info(cred->group_info);
97 free_uid(cred->user);
David Howellsd84f4f92008-11-14 10:39:23 +110098 kmem_cache_free(cred_jar, cred);
David Howellsf1752ee2008-11-14 10:39:17 +110099}
100
101/**
102 * __put_cred - Destroy a set of credentials
David Howellsd84f4f92008-11-14 10:39:23 +1100103 * @cred: The record to release
David Howellsf1752ee2008-11-14 10:39:17 +1100104 *
105 * Destroy a set of credentials on which no references remain.
106 */
107void __put_cred(struct cred *cred)
108{
David Howellsd84f4f92008-11-14 10:39:23 +1100109 BUG_ON(atomic_read(&cred->usage) != 0);
110
David Howellsf1752ee2008-11-14 10:39:17 +1100111 call_rcu(&cred->rcu, put_cred_rcu);
112}
113EXPORT_SYMBOL(__put_cred);
114
David Howellsd84f4f92008-11-14 10:39:23 +1100115/**
116 * prepare_creds - Prepare a new set of credentials for modification
117 *
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().
122 *
123 * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
124 *
125 * Call commit_creds() or abort_creds() to clean up.
David Howellsf1752ee2008-11-14 10:39:17 +1100126 */
David Howellsd84f4f92008-11-14 10:39:23 +1100127struct cred *prepare_creds(void)
David Howellsf1752ee2008-11-14 10:39:17 +1100128{
David Howellsd84f4f92008-11-14 10:39:23 +1100129 struct task_struct *task = current;
130 const struct cred *old;
131 struct cred *new;
David Howellsf1752ee2008-11-14 10:39:17 +1100132
David Howellsd84f4f92008-11-14 10:39:23 +1100133 BUG_ON(atomic_read(&task->cred->usage) < 1);
134
135 new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
136 if (!new)
137 return NULL;
138
139 old = task->cred;
140 memcpy(new, old, sizeof(struct cred));
141
142 atomic_set(&new->usage, 1);
143 get_group_info(new->group_info);
144 get_uid(new->user);
David Howellsf1752ee2008-11-14 10:39:17 +1100145
David Howellsbb952bb2008-11-14 10:39:20 +1100146#ifdef CONFIG_KEYS
David Howellsd84f4f92008-11-14 10:39:23 +1100147 key_get(new->thread_keyring);
148 key_get(new->request_key_auth);
149 atomic_inc(&new->tgcred->usage);
David Howellsbb952bb2008-11-14 10:39:20 +1100150#endif
151
David Howellsf1752ee2008-11-14 10:39:17 +1100152#ifdef CONFIG_SECURITY
David Howellsd84f4f92008-11-14 10:39:23 +1100153 new->security = NULL;
David Howellsf1752ee2008-11-14 10:39:17 +1100154#endif
155
David Howellsd84f4f92008-11-14 10:39:23 +1100156 if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
157 goto error;
158 return new;
159
160error:
161 abort_creds(new);
162 return NULL;
163}
164EXPORT_SYMBOL(prepare_creds);
165
166/*
167 * prepare new credentials for the usermode helper dispatcher
168 */
169struct cred *prepare_usermodehelper_creds(void)
170{
171#ifdef CONFIG_KEYS
172 struct thread_group_cred *tgcred = NULL;
173#endif
174 struct cred *new;
175
176#ifdef CONFIG_KEYS
177 tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);
178 if (!tgcred)
179 return NULL;
180#endif
181
182 new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);
183 if (!new)
184 return NULL;
185
186 memcpy(new, &init_cred, sizeof(struct cred));
187
188 atomic_set(&new->usage, 1);
189 get_group_info(new->group_info);
190 get_uid(new->user);
191
192#ifdef CONFIG_KEYS
193 new->thread_keyring = NULL;
194 new->request_key_auth = NULL;
195 new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT;
196
197 atomic_set(&tgcred->usage, 1);
198 spin_lock_init(&tgcred->lock);
199 new->tgcred = tgcred;
200#endif
201
202#ifdef CONFIG_SECURITY
203 new->security = NULL;
204#endif
205 if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
206 goto error;
207
208 BUG_ON(atomic_read(&new->usage) != 1);
209 return new;
210
211error:
212 put_cred(new);
213 return NULL;
214}
215
216/*
217 * Copy credentials for the new process created by fork()
218 *
219 * We share if we can, but under some circumstances we have to generate a new
220 * set.
221 */
222int copy_creds(struct task_struct *p, unsigned long clone_flags)
223{
224#ifdef CONFIG_KEYS
225 struct thread_group_cred *tgcred;
226#endif
227 struct cred *new;
228
229 mutex_init(&p->cred_exec_mutex);
230
231 if (
232#ifdef CONFIG_KEYS
233 !p->cred->thread_keyring &&
234#endif
235 clone_flags & CLONE_THREAD
236 ) {
237 get_cred(p->cred);
238 atomic_inc(&p->cred->user->processes);
239 return 0;
David Howellsf1752ee2008-11-14 10:39:17 +1100240 }
241
David Howellsd84f4f92008-11-14 10:39:23 +1100242 new = prepare_creds();
243 if (!new)
244 return -ENOMEM;
David Howellsf1752ee2008-11-14 10:39:17 +1100245
David Howellsd84f4f92008-11-14 10:39:23 +1100246#ifdef CONFIG_KEYS
247 /* new threads get their own thread keyrings if their parent already
248 * had one */
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);
254 }
David Howellsf1752ee2008-11-14 10:39:17 +1100255
David Howellsd84f4f92008-11-14 10:39:23 +1100256 /* 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
258 * bit */
259 if (!(clone_flags & CLONE_THREAD)) {
260 tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
261 if (!tgcred) {
262 put_cred(new);
263 return -ENOMEM;
264 }
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);
269
270 release_tgcred(new);
271 new->tgcred = tgcred;
272 }
273#endif
274
275 atomic_inc(&new->user->processes);
276 p->cred = new;
David Howellsf1752ee2008-11-14 10:39:17 +1100277 return 0;
278}
David Howellsd84f4f92008-11-14 10:39:23 +1100279
280/**
281 * commit_creds - Install new credentials upon the current task
282 * @new: The credentials to be assigned
283 *
284 * Install a new set of credentials to the current task, using RCU to replace
285 * the old set.
286 *
287 * This function eats the caller's reference to the new credentials.
288 *
289 * Always returns 0 thus allowing this function to be tail-called at the end
290 * of, say, sys_setgid().
291 */
292int commit_creds(struct cred *new)
293{
294 struct task_struct *task = current;
295 const struct cred *old;
296
297 BUG_ON(atomic_read(&new->usage) < 1);
298 BUG_ON(atomic_read(&task->cred->usage) < 1);
299
300 old = task->cred;
301 security_commit_creds(new, old);
302
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;
311 smp_wmb();
312 }
313
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);
319
320 /* do it
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
325 */
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);
331
332 sched_switch_user(task);
333
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);
340
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);
346
347 put_cred(old);
348 return 0;
349}
350EXPORT_SYMBOL(commit_creds);
351
352/**
353 * abort_creds - Discard a set of credentials and unlock the current task
354 * @new: The credentials that were going to be applied
355 *
356 * Discard a set of credentials that were under construction and unlock the
357 * current task.
358 */
359void abort_creds(struct cred *new)
360{
361 BUG_ON(atomic_read(&new->usage) < 1);
362 put_cred(new);
363}
364EXPORT_SYMBOL(abort_creds);
365
366/**
367 * override_creds - Temporarily override the current process's credentials
368 * @new: The credentials to be assigned
369 *
370 * Install a set of temporary override credentials on the current process,
371 * returning the old set for later reversion.
372 */
373const struct cred *override_creds(const struct cred *new)
374{
375 const struct cred *old = current->cred;
376
377 rcu_assign_pointer(current->cred, get_cred(new));
378 return old;
379}
380EXPORT_SYMBOL(override_creds);
381
382/**
383 * revert_creds - Revert a temporary credentials override
384 * @old: The credentials to be restored
385 *
386 * Revert a temporary set of override credentials to an old set, discarding the
387 * override set.
388 */
389void revert_creds(const struct cred *old)
390{
391 const struct cred *override = current->cred;
392
393 rcu_assign_pointer(current->cred, old);
394 put_cred(override);
395}
396EXPORT_SYMBOL(revert_creds);
397
398/*
399 * initialise the credentials stuff
400 */
401void __init cred_init(void)
402{
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);
406}