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f1752eec DH |
1 | /* 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> | |
d84f4f99 DH |
18 | #include <linux/cn_proc.h> |
19 | #include "cred-internals.h" | |
20 | ||
21 | static struct kmem_cache *cred_jar; | |
f1752eec | 22 | |
bb952bb9 DH |
23 | /* |
24 | * The common credentials for the initial task's thread group | |
25 | */ | |
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, | |
31 | }; | |
32 | #endif | |
33 | ||
f1752eec DH |
34 | /* |
35 | * The initial credentials for the initial task | |
36 | */ | |
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, | |
44 | .user = INIT_USER, | |
45 | .group_info = &init_groups, | |
bb952bb9 DH |
46 | #ifdef CONFIG_KEYS |
47 | .tgcred = &init_tgcred, | |
48 | #endif | |
f1752eec DH |
49 | }; |
50 | ||
bb952bb9 DH |
51 | /* |
52 | * Dispose of the shared task group credentials | |
53 | */ | |
54 | #ifdef CONFIG_KEYS | |
55 | static 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 | */ | |
d84f4f99 | 71 | void release_tgcred(struct cred *cred) |
bb952bb9 DH |
72 | { |
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 | ||
f1752eec DH |
81 | /* |
82 | * The RCU callback to actually dispose of a set of credentials | |
83 | */ | |
84 | static void put_cred_rcu(struct rcu_head *rcu) | |
85 | { | |
86 | struct cred *cred = container_of(rcu, struct cred, rcu); | |
87 | ||
d84f4f99 DH |
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)); | |
f1752eec | 91 | |
d84f4f99 | 92 | security_cred_free(cred); |
f1752eec DH |
93 | key_put(cred->thread_keyring); |
94 | key_put(cred->request_key_auth); | |
bb952bb9 | 95 | release_tgcred(cred); |
f1752eec DH |
96 | put_group_info(cred->group_info); |
97 | free_uid(cred->user); | |
d84f4f99 | 98 | kmem_cache_free(cred_jar, cred); |
f1752eec DH |
99 | } |
100 | ||
101 | /** | |
102 | * __put_cred - Destroy a set of credentials | |
d84f4f99 | 103 | * @cred: The record to release |
f1752eec DH |
104 | * |
105 | * Destroy a set of credentials on which no references remain. | |
106 | */ | |
107 | void __put_cred(struct cred *cred) | |
108 | { | |
d84f4f99 DH |
109 | BUG_ON(atomic_read(&cred->usage) != 0); |
110 | ||
f1752eec DH |
111 | call_rcu(&cred->rcu, put_cred_rcu); |
112 | } | |
113 | EXPORT_SYMBOL(__put_cred); | |
114 | ||
d84f4f99 DH |
115 | /** |
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. | |
126 | */ | |
127 | struct cred *prepare_creds(void) | |
128 | { | |
129 | struct task_struct *task = current; | |
130 | const struct cred *old; | |
131 | struct cred *new; | |
132 | ||
133 | 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); | |
145 | ||
146 | #ifdef CONFIG_KEYS | |
147 | key_get(new->thread_keyring); | |
148 | key_get(new->request_key_auth); | |
149 | atomic_inc(&new->tgcred->usage); | |
150 | #endif | |
151 | ||
152 | #ifdef CONFIG_SECURITY | |
153 | new->security = NULL; | |
154 | #endif | |
155 | ||
156 | if (security_prepare_creds(new, old, GFP_KERNEL) < 0) | |
157 | goto error; | |
158 | return new; | |
159 | ||
160 | error: | |
161 | abort_creds(new); | |
162 | return NULL; | |
163 | } | |
164 | EXPORT_SYMBOL(prepare_creds); | |
165 | ||
166 | /* | |
167 | * prepare new credentials for the usermode helper dispatcher | |
168 | */ | |
169 | struct 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 | ||
211 | error: | |
212 | put_cred(new); | |
213 | return NULL; | |
214 | } | |
215 | ||
f1752eec DH |
216 | /* |
217 | * Copy credentials for the new process created by fork() | |
d84f4f99 DH |
218 | * |
219 | * We share if we can, but under some circumstances we have to generate a new | |
220 | * set. | |
f1752eec DH |
221 | */ |
222 | int copy_creds(struct task_struct *p, unsigned long clone_flags) | |
223 | { | |
d84f4f99 DH |
224 | #ifdef CONFIG_KEYS |
225 | struct thread_group_cred *tgcred; | |
226 | #endif | |
227 | struct cred *new; | |
228 | ||
229 | mutex_init(&p->cred_exec_mutex); | |
f1752eec | 230 | |
d84f4f99 DH |
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; | |
240 | } | |
241 | ||
242 | new = prepare_creds(); | |
243 | if (!new) | |
f1752eec DH |
244 | return -ENOMEM; |
245 | ||
bb952bb9 | 246 | #ifdef CONFIG_KEYS |
d84f4f99 DH |
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 | } | |
255 | ||
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 | |
258 | * bit */ | |
259 | if (!(clone_flags & CLONE_THREAD)) { | |
260 | tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL); | |
261 | if (!tgcred) { | |
262 | put_cred(new); | |
bb952bb9 DH |
263 | return -ENOMEM; |
264 | } | |
d84f4f99 DH |
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; | |
bb952bb9 DH |
272 | } |
273 | #endif | |
274 | ||
d84f4f99 DH |
275 | atomic_inc(&new->user->processes); |
276 | p->cred = new; | |
277 | return 0; | |
278 | } | |
f1752eec | 279 | |
d84f4f99 DH |
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 | */ | |
292 | int 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(); | |
f1752eec DH |
312 | } |
313 | ||
d84f4f99 DH |
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); | |
f1752eec | 340 | |
d84f4f99 DH |
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); | |
f1752eec | 346 | |
d84f4f99 | 347 | put_cred(old); |
f1752eec DH |
348 | return 0; |
349 | } | |
d84f4f99 DH |
350 | EXPORT_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 | */ | |
359 | void abort_creds(struct cred *new) | |
360 | { | |
361 | BUG_ON(atomic_read(&new->usage) < 1); | |
362 | put_cred(new); | |
363 | } | |
364 | EXPORT_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 | */ | |
373 | const 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 | } | |
380 | EXPORT_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 | */ | |
389 | void 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 | } | |
396 | EXPORT_SYMBOL(revert_creds); | |
397 | ||
398 | /* | |
399 | * initialise the credentials stuff | |
400 | */ | |
401 | void __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 | } |