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