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b4d0d230 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
af777cd1 | 2 | /* Task credentials management - see Documentation/security/credentials.rst |
f1752eec DH |
3 | * |
4 | * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. | |
5 | * Written by David Howells (dhowells@redhat.com) | |
f1752eec | 6 | */ |
9984de1a | 7 | #include <linux/export.h> |
f1752eec | 8 | #include <linux/cred.h> |
5a0e3ad6 | 9 | #include <linux/slab.h> |
f1752eec | 10 | #include <linux/sched.h> |
f7ccbae4 | 11 | #include <linux/sched/coredump.h> |
f1752eec DH |
12 | #include <linux/key.h> |
13 | #include <linux/keyctl.h> | |
14 | #include <linux/init_task.h> | |
15 | #include <linux/security.h> | |
40401530 | 16 | #include <linux/binfmts.h> |
d84f4f99 | 17 | #include <linux/cn_proc.h> |
d89b22d4 | 18 | #include <linux/uidgid.h> |
d84f4f99 | 19 | |
e0e81739 | 20 | #if 0 |
52aa8536 JP |
21 | #define kdebug(FMT, ...) \ |
22 | printk("[%-5.5s%5u] " FMT "\n", \ | |
23 | current->comm, current->pid, ##__VA_ARGS__) | |
e0e81739 | 24 | #else |
52aa8536 JP |
25 | #define kdebug(FMT, ...) \ |
26 | do { \ | |
27 | if (0) \ | |
28 | no_printk("[%-5.5s%5u] " FMT "\n", \ | |
29 | current->comm, current->pid, ##__VA_ARGS__); \ | |
30 | } while (0) | |
e0e81739 DH |
31 | #endif |
32 | ||
d84f4f99 | 33 | static struct kmem_cache *cred_jar; |
f1752eec | 34 | |
2813893f | 35 | /* init to 2 - one for init_task, one to ensure it is never freed */ |
32c93976 | 36 | static struct group_info init_groups = { .usage = ATOMIC_INIT(2) }; |
2813893f | 37 | |
f1752eec DH |
38 | /* |
39 | * The initial credentials for the initial task | |
40 | */ | |
41 | struct cred init_cred = { | |
3b11a1de | 42 | .usage = ATOMIC_INIT(4), |
e0e81739 DH |
43 | #ifdef CONFIG_DEBUG_CREDENTIALS |
44 | .subscribers = ATOMIC_INIT(2), | |
45 | .magic = CRED_MAGIC, | |
46 | #endif | |
078de5f7 EB |
47 | .uid = GLOBAL_ROOT_UID, |
48 | .gid = GLOBAL_ROOT_GID, | |
49 | .suid = GLOBAL_ROOT_UID, | |
50 | .sgid = GLOBAL_ROOT_GID, | |
51 | .euid = GLOBAL_ROOT_UID, | |
52 | .egid = GLOBAL_ROOT_GID, | |
53 | .fsuid = GLOBAL_ROOT_UID, | |
54 | .fsgid = GLOBAL_ROOT_GID, | |
f1752eec | 55 | .securebits = SECUREBITS_DEFAULT, |
a3232d2f | 56 | .cap_inheritable = CAP_EMPTY_SET, |
f1752eec | 57 | .cap_permitted = CAP_FULL_SET, |
a3232d2f EP |
58 | .cap_effective = CAP_FULL_SET, |
59 | .cap_bset = CAP_FULL_SET, | |
f1752eec | 60 | .user = INIT_USER, |
47a150ed | 61 | .user_ns = &init_user_ns, |
f1752eec | 62 | .group_info = &init_groups, |
905ae01c | 63 | .ucounts = &init_ucounts, |
f1752eec DH |
64 | }; |
65 | ||
e0e81739 DH |
66 | static inline void set_cred_subscribers(struct cred *cred, int n) |
67 | { | |
68 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
69 | atomic_set(&cred->subscribers, n); | |
70 | #endif | |
71 | } | |
72 | ||
73 | static inline int read_cred_subscribers(const struct cred *cred) | |
74 | { | |
75 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
76 | return atomic_read(&cred->subscribers); | |
77 | #else | |
78 | return 0; | |
79 | #endif | |
80 | } | |
81 | ||
82 | static inline void alter_cred_subscribers(const struct cred *_cred, int n) | |
83 | { | |
84 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
85 | struct cred *cred = (struct cred *) _cred; | |
86 | ||
87 | atomic_add(n, &cred->subscribers); | |
88 | #endif | |
89 | } | |
90 | ||
f1752eec DH |
91 | /* |
92 | * The RCU callback to actually dispose of a set of credentials | |
93 | */ | |
94 | static void put_cred_rcu(struct rcu_head *rcu) | |
95 | { | |
96 | struct cred *cred = container_of(rcu, struct cred, rcu); | |
97 | ||
e0e81739 DH |
98 | kdebug("put_cred_rcu(%p)", cred); |
99 | ||
100 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
101 | if (cred->magic != CRED_MAGIC_DEAD || | |
102 | atomic_read(&cred->usage) != 0 || | |
103 | read_cred_subscribers(cred) != 0) | |
104 | panic("CRED: put_cred_rcu() sees %p with" | |
105 | " mag %x, put %p, usage %d, subscr %d\n", | |
106 | cred, cred->magic, cred->put_addr, | |
107 | atomic_read(&cred->usage), | |
108 | read_cred_subscribers(cred)); | |
109 | #else | |
d84f4f99 DH |
110 | if (atomic_read(&cred->usage) != 0) |
111 | panic("CRED: put_cred_rcu() sees %p with usage %d\n", | |
112 | cred, atomic_read(&cred->usage)); | |
e0e81739 | 113 | #endif |
f1752eec | 114 | |
d84f4f99 | 115 | security_cred_free(cred); |
3a50597d DH |
116 | key_put(cred->session_keyring); |
117 | key_put(cred->process_keyring); | |
f1752eec DH |
118 | key_put(cred->thread_keyring); |
119 | key_put(cred->request_key_auth); | |
4a5d6ba1 DH |
120 | if (cred->group_info) |
121 | put_group_info(cred->group_info); | |
f1752eec | 122 | free_uid(cred->user); |
905ae01c AG |
123 | if (cred->ucounts) |
124 | put_ucounts(cred->ucounts); | |
0093ccb6 | 125 | put_user_ns(cred->user_ns); |
d84f4f99 | 126 | kmem_cache_free(cred_jar, cred); |
f1752eec DH |
127 | } |
128 | ||
129 | /** | |
130 | * __put_cred - Destroy a set of credentials | |
d84f4f99 | 131 | * @cred: The record to release |
f1752eec DH |
132 | * |
133 | * Destroy a set of credentials on which no references remain. | |
134 | */ | |
135 | void __put_cred(struct cred *cred) | |
136 | { | |
e0e81739 DH |
137 | kdebug("__put_cred(%p{%d,%d})", cred, |
138 | atomic_read(&cred->usage), | |
139 | read_cred_subscribers(cred)); | |
140 | ||
d84f4f99 | 141 | BUG_ON(atomic_read(&cred->usage) != 0); |
e0e81739 DH |
142 | #ifdef CONFIG_DEBUG_CREDENTIALS |
143 | BUG_ON(read_cred_subscribers(cred) != 0); | |
144 | cred->magic = CRED_MAGIC_DEAD; | |
145 | cred->put_addr = __builtin_return_address(0); | |
146 | #endif | |
147 | BUG_ON(cred == current->cred); | |
148 | BUG_ON(cred == current->real_cred); | |
d84f4f99 | 149 | |
d7852fbd LT |
150 | if (cred->non_rcu) |
151 | put_cred_rcu(&cred->rcu); | |
152 | else | |
153 | call_rcu(&cred->rcu, put_cred_rcu); | |
f1752eec DH |
154 | } |
155 | EXPORT_SYMBOL(__put_cred); | |
156 | ||
e0e81739 DH |
157 | /* |
158 | * Clean up a task's credentials when it exits | |
159 | */ | |
160 | void exit_creds(struct task_struct *tsk) | |
161 | { | |
162 | struct cred *cred; | |
163 | ||
164 | kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, | |
165 | atomic_read(&tsk->cred->usage), | |
166 | read_cred_subscribers(tsk->cred)); | |
167 | ||
168 | cred = (struct cred *) tsk->real_cred; | |
169 | tsk->real_cred = NULL; | |
170 | validate_creds(cred); | |
171 | alter_cred_subscribers(cred, -1); | |
172 | put_cred(cred); | |
173 | ||
174 | cred = (struct cred *) tsk->cred; | |
175 | tsk->cred = NULL; | |
176 | validate_creds(cred); | |
177 | alter_cred_subscribers(cred, -1); | |
178 | put_cred(cred); | |
7743c48e DH |
179 | |
180 | #ifdef CONFIG_KEYS_REQUEST_CACHE | |
8379bb84 DH |
181 | key_put(tsk->cached_requested_key); |
182 | tsk->cached_requested_key = NULL; | |
7743c48e | 183 | #endif |
ee18d64c DH |
184 | } |
185 | ||
de09a977 DH |
186 | /** |
187 | * get_task_cred - Get another task's objective credentials | |
188 | * @task: The task to query | |
189 | * | |
190 | * Get the objective credentials of a task, pinning them so that they can't go | |
191 | * away. Accessing a task's credentials directly is not permitted. | |
192 | * | |
193 | * The caller must also make sure task doesn't get deleted, either by holding a | |
194 | * ref on task or by holding tasklist_lock to prevent it from being unlinked. | |
195 | */ | |
196 | const struct cred *get_task_cred(struct task_struct *task) | |
197 | { | |
198 | const struct cred *cred; | |
199 | ||
200 | rcu_read_lock(); | |
201 | ||
202 | do { | |
203 | cred = __task_cred((task)); | |
204 | BUG_ON(!cred); | |
97d0fb23 | 205 | } while (!get_cred_rcu(cred)); |
de09a977 DH |
206 | |
207 | rcu_read_unlock(); | |
208 | return cred; | |
209 | } | |
a6d8e763 | 210 | EXPORT_SYMBOL(get_task_cred); |
de09a977 | 211 | |
ee18d64c DH |
212 | /* |
213 | * Allocate blank credentials, such that the credentials can be filled in at a | |
214 | * later date without risk of ENOMEM. | |
215 | */ | |
216 | struct cred *cred_alloc_blank(void) | |
217 | { | |
218 | struct cred *new; | |
219 | ||
220 | new = kmem_cache_zalloc(cred_jar, GFP_KERNEL); | |
221 | if (!new) | |
222 | return NULL; | |
223 | ||
ee18d64c | 224 | atomic_set(&new->usage, 1); |
2edeaa34 TH |
225 | #ifdef CONFIG_DEBUG_CREDENTIALS |
226 | new->magic = CRED_MAGIC; | |
227 | #endif | |
905ae01c | 228 | new->ucounts = get_ucounts(&init_ucounts); |
ee18d64c | 229 | |
84029fd0 | 230 | if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0) |
ee18d64c DH |
231 | goto error; |
232 | ||
ee18d64c DH |
233 | return new; |
234 | ||
235 | error: | |
236 | abort_creds(new); | |
237 | return NULL; | |
e0e81739 DH |
238 | } |
239 | ||
d84f4f99 DH |
240 | /** |
241 | * prepare_creds - Prepare a new set of credentials for modification | |
242 | * | |
243 | * Prepare a new set of task credentials for modification. A task's creds | |
244 | * shouldn't generally be modified directly, therefore this function is used to | |
245 | * prepare a new copy, which the caller then modifies and then commits by | |
246 | * calling commit_creds(). | |
247 | * | |
3b11a1de DH |
248 | * Preparation involves making a copy of the objective creds for modification. |
249 | * | |
d84f4f99 DH |
250 | * Returns a pointer to the new creds-to-be if successful, NULL otherwise. |
251 | * | |
252 | * Call commit_creds() or abort_creds() to clean up. | |
253 | */ | |
254 | struct cred *prepare_creds(void) | |
255 | { | |
256 | struct task_struct *task = current; | |
257 | const struct cred *old; | |
258 | struct cred *new; | |
259 | ||
e0e81739 | 260 | validate_process_creds(); |
d84f4f99 DH |
261 | |
262 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
263 | if (!new) | |
264 | return NULL; | |
265 | ||
e0e81739 DH |
266 | kdebug("prepare_creds() alloc %p", new); |
267 | ||
d84f4f99 DH |
268 | old = task->cred; |
269 | memcpy(new, old, sizeof(struct cred)); | |
270 | ||
d7852fbd | 271 | new->non_rcu = 0; |
d84f4f99 | 272 | atomic_set(&new->usage, 1); |
e0e81739 | 273 | set_cred_subscribers(new, 0); |
d84f4f99 DH |
274 | get_group_info(new->group_info); |
275 | get_uid(new->user); | |
0093ccb6 | 276 | get_user_ns(new->user_ns); |
d84f4f99 DH |
277 | |
278 | #ifdef CONFIG_KEYS | |
3a50597d DH |
279 | key_get(new->session_keyring); |
280 | key_get(new->process_keyring); | |
d84f4f99 DH |
281 | key_get(new->thread_keyring); |
282 | key_get(new->request_key_auth); | |
d84f4f99 DH |
283 | #endif |
284 | ||
285 | #ifdef CONFIG_SECURITY | |
286 | new->security = NULL; | |
287 | #endif | |
288 | ||
84029fd0 | 289 | if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) |
d84f4f99 | 290 | goto error; |
905ae01c AG |
291 | |
292 | new->ucounts = get_ucounts(new->ucounts); | |
293 | if (!new->ucounts) | |
294 | goto error; | |
295 | ||
e0e81739 | 296 | validate_creds(new); |
d84f4f99 DH |
297 | return new; |
298 | ||
299 | error: | |
300 | abort_creds(new); | |
301 | return NULL; | |
302 | } | |
303 | EXPORT_SYMBOL(prepare_creds); | |
304 | ||
a6f76f23 DH |
305 | /* |
306 | * Prepare credentials for current to perform an execve() | |
9b1bf12d | 307 | * - The caller must hold ->cred_guard_mutex |
a6f76f23 DH |
308 | */ |
309 | struct cred *prepare_exec_creds(void) | |
310 | { | |
a6f76f23 DH |
311 | struct cred *new; |
312 | ||
a6f76f23 | 313 | new = prepare_creds(); |
3a50597d | 314 | if (!new) |
a6f76f23 | 315 | return new; |
a6f76f23 DH |
316 | |
317 | #ifdef CONFIG_KEYS | |
318 | /* newly exec'd tasks don't get a thread keyring */ | |
319 | key_put(new->thread_keyring); | |
320 | new->thread_keyring = NULL; | |
321 | ||
a6f76f23 | 322 | /* inherit the session keyring; new process keyring */ |
3a50597d DH |
323 | key_put(new->process_keyring); |
324 | new->process_keyring = NULL; | |
a6f76f23 DH |
325 | #endif |
326 | ||
87b047d2 EB |
327 | new->suid = new->fsuid = new->euid; |
328 | new->sgid = new->fsgid = new->egid; | |
329 | ||
a6f76f23 DH |
330 | return new; |
331 | } | |
332 | ||
f1752eec DH |
333 | /* |
334 | * Copy credentials for the new process created by fork() | |
d84f4f99 DH |
335 | * |
336 | * We share if we can, but under some circumstances we have to generate a new | |
337 | * set. | |
3b11a1de DH |
338 | * |
339 | * The new process gets the current process's subjective credentials as its | |
340 | * objective and subjective credentials | |
f1752eec DH |
341 | */ |
342 | int copy_creds(struct task_struct *p, unsigned long clone_flags) | |
343 | { | |
d84f4f99 | 344 | struct cred *new; |
18b6e041 | 345 | int ret; |
d84f4f99 | 346 | |
7743c48e DH |
347 | #ifdef CONFIG_KEYS_REQUEST_CACHE |
348 | p->cached_requested_key = NULL; | |
349 | #endif | |
350 | ||
d84f4f99 DH |
351 | if ( |
352 | #ifdef CONFIG_KEYS | |
353 | !p->cred->thread_keyring && | |
354 | #endif | |
355 | clone_flags & CLONE_THREAD | |
356 | ) { | |
3b11a1de | 357 | p->real_cred = get_cred(p->cred); |
d84f4f99 | 358 | get_cred(p->cred); |
e0e81739 DH |
359 | alter_cred_subscribers(p->cred, 2); |
360 | kdebug("share_creds(%p{%d,%d})", | |
361 | p->cred, atomic_read(&p->cred->usage), | |
362 | read_cred_subscribers(p->cred)); | |
21d1c5e3 | 363 | inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); |
d84f4f99 DH |
364 | return 0; |
365 | } | |
366 | ||
367 | new = prepare_creds(); | |
368 | if (!new) | |
f1752eec DH |
369 | return -ENOMEM; |
370 | ||
18b6e041 SH |
371 | if (clone_flags & CLONE_NEWUSER) { |
372 | ret = create_user_ns(new); | |
373 | if (ret < 0) | |
374 | goto error_put; | |
5e6b8a50 YY |
375 | ret = set_cred_ucounts(new); |
376 | if (ret < 0) | |
905ae01c | 377 | goto error_put; |
18b6e041 SH |
378 | } |
379 | ||
bb952bb9 | 380 | #ifdef CONFIG_KEYS |
d84f4f99 DH |
381 | /* new threads get their own thread keyrings if their parent already |
382 | * had one */ | |
383 | if (new->thread_keyring) { | |
384 | key_put(new->thread_keyring); | |
385 | new->thread_keyring = NULL; | |
386 | if (clone_flags & CLONE_THREAD) | |
387 | install_thread_keyring_to_cred(new); | |
388 | } | |
389 | ||
3a50597d DH |
390 | /* The process keyring is only shared between the threads in a process; |
391 | * anything outside of those threads doesn't inherit. | |
392 | */ | |
d84f4f99 | 393 | if (!(clone_flags & CLONE_THREAD)) { |
3a50597d DH |
394 | key_put(new->process_keyring); |
395 | new->process_keyring = NULL; | |
bb952bb9 DH |
396 | } |
397 | #endif | |
398 | ||
3b11a1de | 399 | p->cred = p->real_cred = get_cred(new); |
21d1c5e3 | 400 | inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1); |
e0e81739 DH |
401 | alter_cred_subscribers(new, 2); |
402 | validate_creds(new); | |
d84f4f99 | 403 | return 0; |
18b6e041 SH |
404 | |
405 | error_put: | |
406 | put_cred(new); | |
407 | return ret; | |
d84f4f99 | 408 | } |
f1752eec | 409 | |
aa6d054e EB |
410 | static bool cred_cap_issubset(const struct cred *set, const struct cred *subset) |
411 | { | |
412 | const struct user_namespace *set_ns = set->user_ns; | |
413 | const struct user_namespace *subset_ns = subset->user_ns; | |
414 | ||
415 | /* If the two credentials are in the same user namespace see if | |
416 | * the capabilities of subset are a subset of set. | |
417 | */ | |
418 | if (set_ns == subset_ns) | |
419 | return cap_issubset(subset->cap_permitted, set->cap_permitted); | |
420 | ||
421 | /* The credentials are in a different user namespaces | |
422 | * therefore one is a subset of the other only if a set is an | |
423 | * ancestor of subset and set->euid is owner of subset or one | |
424 | * of subsets ancestors. | |
425 | */ | |
426 | for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) { | |
427 | if ((set_ns == subset_ns->parent) && | |
428 | uid_eq(subset_ns->owner, set->euid)) | |
429 | return true; | |
430 | } | |
431 | ||
432 | return false; | |
433 | } | |
434 | ||
d84f4f99 DH |
435 | /** |
436 | * commit_creds - Install new credentials upon the current task | |
437 | * @new: The credentials to be assigned | |
438 | * | |
439 | * Install a new set of credentials to the current task, using RCU to replace | |
3b11a1de DH |
440 | * the old set. Both the objective and the subjective credentials pointers are |
441 | * updated. This function may not be called if the subjective credentials are | |
442 | * in an overridden state. | |
d84f4f99 DH |
443 | * |
444 | * This function eats the caller's reference to the new credentials. | |
445 | * | |
446 | * Always returns 0 thus allowing this function to be tail-called at the end | |
447 | * of, say, sys_setgid(). | |
448 | */ | |
449 | int commit_creds(struct cred *new) | |
450 | { | |
451 | struct task_struct *task = current; | |
e0e81739 | 452 | const struct cred *old = task->real_cred; |
d84f4f99 | 453 | |
e0e81739 DH |
454 | kdebug("commit_creds(%p{%d,%d})", new, |
455 | atomic_read(&new->usage), | |
456 | read_cred_subscribers(new)); | |
457 | ||
458 | BUG_ON(task->cred != old); | |
459 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
460 | BUG_ON(read_cred_subscribers(old) < 2); | |
461 | validate_creds(old); | |
462 | validate_creds(new); | |
463 | #endif | |
d84f4f99 | 464 | BUG_ON(atomic_read(&new->usage) < 1); |
d84f4f99 | 465 | |
3b11a1de DH |
466 | get_cred(new); /* we will require a ref for the subj creds too */ |
467 | ||
d84f4f99 | 468 | /* dumpability changes */ |
078de5f7 EB |
469 | if (!uid_eq(old->euid, new->euid) || |
470 | !gid_eq(old->egid, new->egid) || | |
471 | !uid_eq(old->fsuid, new->fsuid) || | |
472 | !gid_eq(old->fsgid, new->fsgid) || | |
aa6d054e | 473 | !cred_cap_issubset(old, new)) { |
b9456371 DH |
474 | if (task->mm) |
475 | set_dumpable(task->mm, suid_dumpable); | |
d84f4f99 | 476 | task->pdeath_signal = 0; |
f6581f5b JH |
477 | /* |
478 | * If a task drops privileges and becomes nondumpable, | |
479 | * the dumpability change must become visible before | |
480 | * the credential change; otherwise, a __ptrace_may_access() | |
481 | * racing with this change may be able to attach to a task it | |
482 | * shouldn't be able to attach to (as if the task had dropped | |
483 | * privileges without becoming nondumpable). | |
484 | * Pairs with a read barrier in __ptrace_may_access(). | |
485 | */ | |
d84f4f99 | 486 | smp_wmb(); |
f1752eec DH |
487 | } |
488 | ||
d84f4f99 | 489 | /* alter the thread keyring */ |
078de5f7 | 490 | if (!uid_eq(new->fsuid, old->fsuid)) |
2e21865f | 491 | key_fsuid_changed(new); |
078de5f7 | 492 | if (!gid_eq(new->fsgid, old->fsgid)) |
2e21865f | 493 | key_fsgid_changed(new); |
d84f4f99 DH |
494 | |
495 | /* do it | |
72fa5997 VK |
496 | * RLIMIT_NPROC limits on user->processes have already been checked |
497 | * in set_user(). | |
d84f4f99 | 498 | */ |
e0e81739 | 499 | alter_cred_subscribers(new, 2); |
21d1c5e3 AG |
500 | if (new->user != old->user || new->user_ns != old->user_ns) |
501 | inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1); | |
3b11a1de | 502 | rcu_assign_pointer(task->real_cred, new); |
d84f4f99 DH |
503 | rcu_assign_pointer(task->cred, new); |
504 | if (new->user != old->user) | |
21d1c5e3 | 505 | dec_rlimit_ucounts(old->ucounts, UCOUNT_RLIMIT_NPROC, 1); |
e0e81739 | 506 | alter_cred_subscribers(old, -2); |
d84f4f99 | 507 | |
d84f4f99 | 508 | /* send notifications */ |
078de5f7 EB |
509 | if (!uid_eq(new->uid, old->uid) || |
510 | !uid_eq(new->euid, old->euid) || | |
511 | !uid_eq(new->suid, old->suid) || | |
512 | !uid_eq(new->fsuid, old->fsuid)) | |
d84f4f99 | 513 | proc_id_connector(task, PROC_EVENT_UID); |
f1752eec | 514 | |
078de5f7 EB |
515 | if (!gid_eq(new->gid, old->gid) || |
516 | !gid_eq(new->egid, old->egid) || | |
517 | !gid_eq(new->sgid, old->sgid) || | |
518 | !gid_eq(new->fsgid, old->fsgid)) | |
d84f4f99 | 519 | proc_id_connector(task, PROC_EVENT_GID); |
f1752eec | 520 | |
3b11a1de DH |
521 | /* release the old obj and subj refs both */ |
522 | put_cred(old); | |
d84f4f99 | 523 | put_cred(old); |
f1752eec DH |
524 | return 0; |
525 | } | |
d84f4f99 DH |
526 | EXPORT_SYMBOL(commit_creds); |
527 | ||
528 | /** | |
529 | * abort_creds - Discard a set of credentials and unlock the current task | |
530 | * @new: The credentials that were going to be applied | |
531 | * | |
532 | * Discard a set of credentials that were under construction and unlock the | |
533 | * current task. | |
534 | */ | |
535 | void abort_creds(struct cred *new) | |
536 | { | |
e0e81739 DH |
537 | kdebug("abort_creds(%p{%d,%d})", new, |
538 | atomic_read(&new->usage), | |
539 | read_cred_subscribers(new)); | |
540 | ||
541 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
542 | BUG_ON(read_cred_subscribers(new) != 0); | |
543 | #endif | |
d84f4f99 DH |
544 | BUG_ON(atomic_read(&new->usage) < 1); |
545 | put_cred(new); | |
546 | } | |
547 | EXPORT_SYMBOL(abort_creds); | |
548 | ||
549 | /** | |
3b11a1de | 550 | * override_creds - Override the current process's subjective credentials |
d84f4f99 DH |
551 | * @new: The credentials to be assigned |
552 | * | |
3b11a1de DH |
553 | * Install a set of temporary override subjective credentials on the current |
554 | * process, returning the old set for later reversion. | |
d84f4f99 DH |
555 | */ |
556 | const struct cred *override_creds(const struct cred *new) | |
557 | { | |
558 | const struct cred *old = current->cred; | |
559 | ||
e0e81739 DH |
560 | kdebug("override_creds(%p{%d,%d})", new, |
561 | atomic_read(&new->usage), | |
562 | read_cred_subscribers(new)); | |
563 | ||
564 | validate_creds(old); | |
565 | validate_creds(new); | |
d7852fbd LT |
566 | |
567 | /* | |
568 | * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'. | |
569 | * | |
570 | * That means that we do not clear the 'non_rcu' flag, since | |
571 | * we are only installing the cred into the thread-synchronous | |
572 | * '->cred' pointer, not the '->real_cred' pointer that is | |
573 | * visible to other threads under RCU. | |
574 | * | |
575 | * Also note that we did validate_creds() manually, not depending | |
576 | * on the validation in 'get_cred()'. | |
577 | */ | |
578 | get_new_cred((struct cred *)new); | |
e0e81739 DH |
579 | alter_cred_subscribers(new, 1); |
580 | rcu_assign_pointer(current->cred, new); | |
581 | alter_cred_subscribers(old, -1); | |
582 | ||
583 | kdebug("override_creds() = %p{%d,%d}", old, | |
584 | atomic_read(&old->usage), | |
585 | read_cred_subscribers(old)); | |
d84f4f99 DH |
586 | return old; |
587 | } | |
588 | EXPORT_SYMBOL(override_creds); | |
589 | ||
590 | /** | |
3b11a1de | 591 | * revert_creds - Revert a temporary subjective credentials override |
d84f4f99 DH |
592 | * @old: The credentials to be restored |
593 | * | |
3b11a1de DH |
594 | * Revert a temporary set of override subjective credentials to an old set, |
595 | * discarding the override set. | |
d84f4f99 DH |
596 | */ |
597 | void revert_creds(const struct cred *old) | |
598 | { | |
599 | const struct cred *override = current->cred; | |
600 | ||
e0e81739 DH |
601 | kdebug("revert_creds(%p{%d,%d})", old, |
602 | atomic_read(&old->usage), | |
603 | read_cred_subscribers(old)); | |
604 | ||
605 | validate_creds(old); | |
606 | validate_creds(override); | |
607 | alter_cred_subscribers(old, 1); | |
d84f4f99 | 608 | rcu_assign_pointer(current->cred, old); |
e0e81739 | 609 | alter_cred_subscribers(override, -1); |
d84f4f99 DH |
610 | put_cred(override); |
611 | } | |
612 | EXPORT_SYMBOL(revert_creds); | |
613 | ||
d89b22d4 N |
614 | /** |
615 | * cred_fscmp - Compare two credentials with respect to filesystem access. | |
616 | * @a: The first credential | |
617 | * @b: The second credential | |
618 | * | |
619 | * cred_cmp() will return zero if both credentials have the same | |
620 | * fsuid, fsgid, and supplementary groups. That is, if they will both | |
621 | * provide the same access to files based on mode/uid/gid. | |
622 | * If the credentials are different, then either -1 or 1 will | |
623 | * be returned depending on whether @a comes before or after @b | |
624 | * respectively in an arbitrary, but stable, ordering of credentials. | |
625 | * | |
626 | * Return: -1, 0, or 1 depending on comparison | |
627 | */ | |
628 | int cred_fscmp(const struct cred *a, const struct cred *b) | |
629 | { | |
630 | struct group_info *ga, *gb; | |
631 | int g; | |
632 | ||
633 | if (a == b) | |
634 | return 0; | |
635 | if (uid_lt(a->fsuid, b->fsuid)) | |
636 | return -1; | |
637 | if (uid_gt(a->fsuid, b->fsuid)) | |
638 | return 1; | |
639 | ||
640 | if (gid_lt(a->fsgid, b->fsgid)) | |
641 | return -1; | |
642 | if (gid_gt(a->fsgid, b->fsgid)) | |
643 | return 1; | |
644 | ||
645 | ga = a->group_info; | |
646 | gb = b->group_info; | |
647 | if (ga == gb) | |
648 | return 0; | |
649 | if (ga == NULL) | |
650 | return -1; | |
651 | if (gb == NULL) | |
652 | return 1; | |
653 | if (ga->ngroups < gb->ngroups) | |
654 | return -1; | |
655 | if (ga->ngroups > gb->ngroups) | |
656 | return 1; | |
657 | ||
658 | for (g = 0; g < ga->ngroups; g++) { | |
659 | if (gid_lt(ga->gid[g], gb->gid[g])) | |
660 | return -1; | |
661 | if (gid_gt(ga->gid[g], gb->gid[g])) | |
662 | return 1; | |
663 | } | |
664 | return 0; | |
665 | } | |
666 | EXPORT_SYMBOL(cred_fscmp); | |
667 | ||
905ae01c AG |
668 | int set_cred_ucounts(struct cred *new) |
669 | { | |
670 | struct task_struct *task = current; | |
671 | const struct cred *old = task->real_cred; | |
672 | struct ucounts *old_ucounts = new->ucounts; | |
673 | ||
674 | if (new->user == old->user && new->user_ns == old->user_ns) | |
675 | return 0; | |
676 | ||
677 | /* | |
678 | * This optimization is needed because alloc_ucounts() uses locks | |
679 | * for table lookups. | |
680 | */ | |
681 | if (old_ucounts && old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid)) | |
682 | return 0; | |
683 | ||
684 | if (!(new->ucounts = alloc_ucounts(new->user_ns, new->euid))) | |
685 | return -EAGAIN; | |
686 | ||
687 | if (old_ucounts) | |
688 | put_ucounts(old_ucounts); | |
689 | ||
690 | return 0; | |
691 | } | |
692 | ||
d84f4f99 DH |
693 | /* |
694 | * initialise the credentials stuff | |
695 | */ | |
696 | void __init cred_init(void) | |
697 | { | |
698 | /* allocate a slab in which we can store credentials */ | |
5d097056 VD |
699 | cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0, |
700 | SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); | |
d84f4f99 | 701 | } |
3a3b7ce9 DH |
702 | |
703 | /** | |
704 | * prepare_kernel_cred - Prepare a set of credentials for a kernel service | |
705 | * @daemon: A userspace daemon to be used as a reference | |
706 | * | |
707 | * Prepare a set of credentials for a kernel service. This can then be used to | |
708 | * override a task's own credentials so that work can be done on behalf of that | |
709 | * task that requires a different subjective context. | |
710 | * | |
711 | * @daemon is used to provide a base for the security record, but can be NULL. | |
712 | * If @daemon is supplied, then the security data will be derived from that; | |
713 | * otherwise they'll be set to 0 and no groups, full capabilities and no keys. | |
714 | * | |
715 | * The caller may change these controls afterwards if desired. | |
716 | * | |
717 | * Returns the new credentials or NULL if out of memory. | |
3a3b7ce9 DH |
718 | */ |
719 | struct cred *prepare_kernel_cred(struct task_struct *daemon) | |
720 | { | |
721 | const struct cred *old; | |
722 | struct cred *new; | |
723 | ||
724 | new = kmem_cache_alloc(cred_jar, GFP_KERNEL); | |
725 | if (!new) | |
726 | return NULL; | |
727 | ||
e0e81739 DH |
728 | kdebug("prepare_kernel_cred() alloc %p", new); |
729 | ||
3a3b7ce9 DH |
730 | if (daemon) |
731 | old = get_task_cred(daemon); | |
732 | else | |
733 | old = get_cred(&init_cred); | |
734 | ||
e0e81739 DH |
735 | validate_creds(old); |
736 | ||
43529c97 | 737 | *new = *old; |
d7852fbd | 738 | new->non_rcu = 0; |
fb2b2a1d TH |
739 | atomic_set(&new->usage, 1); |
740 | set_cred_subscribers(new, 0); | |
3a3b7ce9 | 741 | get_uid(new->user); |
0093ccb6 | 742 | get_user_ns(new->user_ns); |
3a3b7ce9 DH |
743 | get_group_info(new->group_info); |
744 | ||
745 | #ifdef CONFIG_KEYS | |
3a50597d DH |
746 | new->session_keyring = NULL; |
747 | new->process_keyring = NULL; | |
3a3b7ce9 | 748 | new->thread_keyring = NULL; |
3a50597d | 749 | new->request_key_auth = NULL; |
3a3b7ce9 DH |
750 | new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |
751 | #endif | |
752 | ||
753 | #ifdef CONFIG_SECURITY | |
754 | new->security = NULL; | |
755 | #endif | |
84029fd0 | 756 | if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0) |
3a3b7ce9 DH |
757 | goto error; |
758 | ||
905ae01c AG |
759 | new->ucounts = get_ucounts(new->ucounts); |
760 | if (!new->ucounts) | |
761 | goto error; | |
762 | ||
3a3b7ce9 | 763 | put_cred(old); |
e0e81739 | 764 | validate_creds(new); |
3a3b7ce9 DH |
765 | return new; |
766 | ||
767 | error: | |
768 | put_cred(new); | |
0de33681 | 769 | put_cred(old); |
3a3b7ce9 DH |
770 | return NULL; |
771 | } | |
772 | EXPORT_SYMBOL(prepare_kernel_cred); | |
773 | ||
774 | /** | |
775 | * set_security_override - Set the security ID in a set of credentials | |
776 | * @new: The credentials to alter | |
777 | * @secid: The LSM security ID to set | |
778 | * | |
779 | * Set the LSM security ID in a set of credentials so that the subjective | |
780 | * security is overridden when an alternative set of credentials is used. | |
781 | */ | |
782 | int set_security_override(struct cred *new, u32 secid) | |
783 | { | |
784 | return security_kernel_act_as(new, secid); | |
785 | } | |
786 | EXPORT_SYMBOL(set_security_override); | |
787 | ||
788 | /** | |
789 | * set_security_override_from_ctx - Set the security ID in a set of credentials | |
790 | * @new: The credentials to alter | |
791 | * @secctx: The LSM security context to generate the security ID from. | |
792 | * | |
793 | * Set the LSM security ID in a set of credentials so that the subjective | |
794 | * security is overridden when an alternative set of credentials is used. The | |
795 | * security ID is specified in string form as a security context to be | |
796 | * interpreted by the LSM. | |
797 | */ | |
798 | int set_security_override_from_ctx(struct cred *new, const char *secctx) | |
799 | { | |
800 | u32 secid; | |
801 | int ret; | |
802 | ||
803 | ret = security_secctx_to_secid(secctx, strlen(secctx), &secid); | |
804 | if (ret < 0) | |
805 | return ret; | |
806 | ||
807 | return set_security_override(new, secid); | |
808 | } | |
809 | EXPORT_SYMBOL(set_security_override_from_ctx); | |
810 | ||
811 | /** | |
812 | * set_create_files_as - Set the LSM file create context in a set of credentials | |
813 | * @new: The credentials to alter | |
814 | * @inode: The inode to take the context from | |
815 | * | |
816 | * Change the LSM file creation context in a set of credentials to be the same | |
817 | * as the object context of the specified inode, so that the new inodes have | |
818 | * the same MAC context as that inode. | |
819 | */ | |
820 | int set_create_files_as(struct cred *new, struct inode *inode) | |
821 | { | |
5f65e5ca SF |
822 | if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid)) |
823 | return -EINVAL; | |
3a3b7ce9 DH |
824 | new->fsuid = inode->i_uid; |
825 | new->fsgid = inode->i_gid; | |
826 | return security_kernel_create_files_as(new, inode); | |
827 | } | |
828 | EXPORT_SYMBOL(set_create_files_as); | |
e0e81739 DH |
829 | |
830 | #ifdef CONFIG_DEBUG_CREDENTIALS | |
831 | ||
74908a00 AM |
832 | bool creds_are_invalid(const struct cred *cred) |
833 | { | |
834 | if (cred->magic != CRED_MAGIC) | |
835 | return true; | |
74908a00 AM |
836 | return false; |
837 | } | |
764db03f | 838 | EXPORT_SYMBOL(creds_are_invalid); |
74908a00 | 839 | |
e0e81739 DH |
840 | /* |
841 | * dump invalid credentials | |
842 | */ | |
843 | static void dump_invalid_creds(const struct cred *cred, const char *label, | |
844 | const struct task_struct *tsk) | |
845 | { | |
846 | printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n", | |
847 | label, cred, | |
848 | cred == &init_cred ? "[init]" : "", | |
849 | cred == tsk->real_cred ? "[real]" : "", | |
850 | cred == tsk->cred ? "[eff]" : ""); | |
851 | printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n", | |
852 | cred->magic, cred->put_addr); | |
853 | printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n", | |
854 | atomic_read(&cred->usage), | |
855 | read_cred_subscribers(cred)); | |
856 | printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n", | |
c9235f48 EB |
857 | from_kuid_munged(&init_user_ns, cred->uid), |
858 | from_kuid_munged(&init_user_ns, cred->euid), | |
859 | from_kuid_munged(&init_user_ns, cred->suid), | |
860 | from_kuid_munged(&init_user_ns, cred->fsuid)); | |
e0e81739 | 861 | printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n", |
c9235f48 EB |
862 | from_kgid_munged(&init_user_ns, cred->gid), |
863 | from_kgid_munged(&init_user_ns, cred->egid), | |
864 | from_kgid_munged(&init_user_ns, cred->sgid), | |
865 | from_kgid_munged(&init_user_ns, cred->fsgid)); | |
e0e81739 DH |
866 | #ifdef CONFIG_SECURITY |
867 | printk(KERN_ERR "CRED: ->security is %p\n", cred->security); | |
868 | if ((unsigned long) cred->security >= PAGE_SIZE && | |
869 | (((unsigned long) cred->security & 0xffffff00) != | |
870 | (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))) | |
871 | printk(KERN_ERR "CRED: ->security {%x, %x}\n", | |
872 | ((u32*)cred->security)[0], | |
873 | ((u32*)cred->security)[1]); | |
874 | #endif | |
875 | } | |
876 | ||
877 | /* | |
878 | * report use of invalid credentials | |
879 | */ | |
880 | void __invalid_creds(const struct cred *cred, const char *file, unsigned line) | |
881 | { | |
882 | printk(KERN_ERR "CRED: Invalid credentials\n"); | |
883 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); | |
884 | dump_invalid_creds(cred, "Specified", current); | |
885 | BUG(); | |
886 | } | |
887 | EXPORT_SYMBOL(__invalid_creds); | |
888 | ||
889 | /* | |
890 | * check the credentials on a process | |
891 | */ | |
892 | void __validate_process_creds(struct task_struct *tsk, | |
893 | const char *file, unsigned line) | |
894 | { | |
895 | if (tsk->cred == tsk->real_cred) { | |
896 | if (unlikely(read_cred_subscribers(tsk->cred) < 2 || | |
897 | creds_are_invalid(tsk->cred))) | |
898 | goto invalid_creds; | |
899 | } else { | |
900 | if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 || | |
901 | read_cred_subscribers(tsk->cred) < 1 || | |
902 | creds_are_invalid(tsk->real_cred) || | |
903 | creds_are_invalid(tsk->cred))) | |
904 | goto invalid_creds; | |
905 | } | |
906 | return; | |
907 | ||
908 | invalid_creds: | |
909 | printk(KERN_ERR "CRED: Invalid process credentials\n"); | |
910 | printk(KERN_ERR "CRED: At %s:%u\n", file, line); | |
911 | ||
912 | dump_invalid_creds(tsk->real_cred, "Real", tsk); | |
913 | if (tsk->cred != tsk->real_cred) | |
914 | dump_invalid_creds(tsk->cred, "Effective", tsk); | |
915 | else | |
916 | printk(KERN_ERR "CRED: Effective creds == Real creds\n"); | |
917 | BUG(); | |
918 | } | |
919 | EXPORT_SYMBOL(__validate_process_creds); | |
920 | ||
921 | /* | |
922 | * check creds for do_exit() | |
923 | */ | |
924 | void validate_creds_for_do_exit(struct task_struct *tsk) | |
925 | { | |
926 | kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})", | |
927 | tsk->real_cred, tsk->cred, | |
928 | atomic_read(&tsk->cred->usage), | |
929 | read_cred_subscribers(tsk->cred)); | |
930 | ||
931 | __validate_process_creds(tsk, __FILE__, __LINE__); | |
932 | } | |
933 | ||
934 | #endif /* CONFIG_DEBUG_CREDENTIALS */ |