Merge tag '6.1-rc4-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6
[linux-2.6-microblaze.git] / security / keys / process_keys.c
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Manage a process's keyrings
3  *
4  * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  */
7
8 #include <linux/init.h>
9 #include <linux/sched.h>
10 #include <linux/sched/user.h>
11 #include <linux/keyctl.h>
12 #include <linux/fs.h>
13 #include <linux/err.h>
14 #include <linux/mutex.h>
15 #include <linux/security.h>
16 #include <linux/user_namespace.h>
17 #include <linux/uaccess.h>
18 #include <linux/init_task.h>
19 #include <keys/request_key_auth-type.h>
20 #include "internal.h"
21
22 /* Session keyring create vs join semaphore */
23 static DEFINE_MUTEX(key_session_mutex);
24
25 /* The root user's tracking struct */
26 struct key_user root_key_user = {
27         .usage          = REFCOUNT_INIT(3),
28         .cons_lock      = __MUTEX_INITIALIZER(root_key_user.cons_lock),
29         .lock           = __SPIN_LOCK_UNLOCKED(root_key_user.lock),
30         .nkeys          = ATOMIC_INIT(2),
31         .nikeys         = ATOMIC_INIT(2),
32         .uid            = GLOBAL_ROOT_UID,
33 };
34
35 /*
36  * Get or create a user register keyring.
37  */
38 static struct key *get_user_register(struct user_namespace *user_ns)
39 {
40         struct key *reg_keyring = READ_ONCE(user_ns->user_keyring_register);
41
42         if (reg_keyring)
43                 return reg_keyring;
44
45         down_write(&user_ns->keyring_sem);
46
47         /* Make sure there's a register keyring.  It gets owned by the
48          * user_namespace's owner.
49          */
50         reg_keyring = user_ns->user_keyring_register;
51         if (!reg_keyring) {
52                 reg_keyring = keyring_alloc(".user_reg",
53                                             user_ns->owner, INVALID_GID,
54                                             &init_cred,
55                                             KEY_POS_WRITE | KEY_POS_SEARCH |
56                                             KEY_USR_VIEW | KEY_USR_READ,
57                                             0,
58                                             NULL, NULL);
59                 if (!IS_ERR(reg_keyring))
60                         smp_store_release(&user_ns->user_keyring_register,
61                                           reg_keyring);
62         }
63
64         up_write(&user_ns->keyring_sem);
65
66         /* We don't return a ref since the keyring is pinned by the user_ns */
67         return reg_keyring;
68 }
69
70 /*
71  * Look up the user and user session keyrings for the current process's UID,
72  * creating them if they don't exist.
73  */
74 int look_up_user_keyrings(struct key **_user_keyring,
75                           struct key **_user_session_keyring)
76 {
77         const struct cred *cred = current_cred();
78         struct user_namespace *user_ns = current_user_ns();
79         struct key *reg_keyring, *uid_keyring, *session_keyring;
80         key_perm_t user_keyring_perm;
81         key_ref_t uid_keyring_r, session_keyring_r;
82         uid_t uid = from_kuid(user_ns, cred->user->uid);
83         char buf[20];
84         int ret;
85
86         user_keyring_perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL;
87
88         kenter("%u", uid);
89
90         reg_keyring = get_user_register(user_ns);
91         if (IS_ERR(reg_keyring))
92                 return PTR_ERR(reg_keyring);
93
94         down_write(&user_ns->keyring_sem);
95         ret = 0;
96
97         /* Get the user keyring.  Note that there may be one in existence
98          * already as it may have been pinned by a session, but the user_struct
99          * pointing to it may have been destroyed by setuid.
100          */
101         snprintf(buf, sizeof(buf), "_uid.%u", uid);
102         uid_keyring_r = keyring_search(make_key_ref(reg_keyring, true),
103                                        &key_type_keyring, buf, false);
104         kdebug("_uid %p", uid_keyring_r);
105         if (uid_keyring_r == ERR_PTR(-EAGAIN)) {
106                 uid_keyring = keyring_alloc(buf, cred->user->uid, INVALID_GID,
107                                             cred, user_keyring_perm,
108                                             KEY_ALLOC_UID_KEYRING |
109                                             KEY_ALLOC_IN_QUOTA,
110                                             NULL, reg_keyring);
111                 if (IS_ERR(uid_keyring)) {
112                         ret = PTR_ERR(uid_keyring);
113                         goto error;
114                 }
115         } else if (IS_ERR(uid_keyring_r)) {
116                 ret = PTR_ERR(uid_keyring_r);
117                 goto error;
118         } else {
119                 uid_keyring = key_ref_to_ptr(uid_keyring_r);
120         }
121
122         /* Get a default session keyring (which might also exist already) */
123         snprintf(buf, sizeof(buf), "_uid_ses.%u", uid);
124         session_keyring_r = keyring_search(make_key_ref(reg_keyring, true),
125                                            &key_type_keyring, buf, false);
126         kdebug("_uid_ses %p", session_keyring_r);
127         if (session_keyring_r == ERR_PTR(-EAGAIN)) {
128                 session_keyring = keyring_alloc(buf, cred->user->uid, INVALID_GID,
129                                                 cred, user_keyring_perm,
130                                                 KEY_ALLOC_UID_KEYRING |
131                                                 KEY_ALLOC_IN_QUOTA,
132                                                 NULL, NULL);
133                 if (IS_ERR(session_keyring)) {
134                         ret = PTR_ERR(session_keyring);
135                         goto error_release;
136                 }
137
138                 /* We install a link from the user session keyring to
139                  * the user keyring.
140                  */
141                 ret = key_link(session_keyring, uid_keyring);
142                 if (ret < 0)
143                         goto error_release_session;
144
145                 /* And only then link the user-session keyring to the
146                  * register.
147                  */
148                 ret = key_link(reg_keyring, session_keyring);
149                 if (ret < 0)
150                         goto error_release_session;
151         } else if (IS_ERR(session_keyring_r)) {
152                 ret = PTR_ERR(session_keyring_r);
153                 goto error_release;
154         } else {
155                 session_keyring = key_ref_to_ptr(session_keyring_r);
156         }
157
158         up_write(&user_ns->keyring_sem);
159
160         if (_user_session_keyring)
161                 *_user_session_keyring = session_keyring;
162         else
163                 key_put(session_keyring);
164         if (_user_keyring)
165                 *_user_keyring = uid_keyring;
166         else
167                 key_put(uid_keyring);
168         kleave(" = 0");
169         return 0;
170
171 error_release_session:
172         key_put(session_keyring);
173 error_release:
174         key_put(uid_keyring);
175 error:
176         up_write(&user_ns->keyring_sem);
177         kleave(" = %d", ret);
178         return ret;
179 }
180
181 /*
182  * Get the user session keyring if it exists, but don't create it if it
183  * doesn't.
184  */
185 struct key *get_user_session_keyring_rcu(const struct cred *cred)
186 {
187         struct key *reg_keyring = READ_ONCE(cred->user_ns->user_keyring_register);
188         key_ref_t session_keyring_r;
189         char buf[20];
190
191         struct keyring_search_context ctx = {
192                 .index_key.type         = &key_type_keyring,
193                 .index_key.description  = buf,
194                 .cred                   = cred,
195                 .match_data.cmp         = key_default_cmp,
196                 .match_data.raw_data    = buf,
197                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
198                 .flags                  = KEYRING_SEARCH_DO_STATE_CHECK,
199         };
200
201         if (!reg_keyring)
202                 return NULL;
203
204         ctx.index_key.desc_len = snprintf(buf, sizeof(buf), "_uid_ses.%u",
205                                           from_kuid(cred->user_ns,
206                                                     cred->user->uid));
207
208         session_keyring_r = keyring_search_rcu(make_key_ref(reg_keyring, true),
209                                                &ctx);
210         if (IS_ERR(session_keyring_r))
211                 return NULL;
212         return key_ref_to_ptr(session_keyring_r);
213 }
214
215 /*
216  * Install a thread keyring to the given credentials struct if it didn't have
217  * one already.  This is allowed to overrun the quota.
218  *
219  * Return: 0 if a thread keyring is now present; -errno on failure.
220  */
221 int install_thread_keyring_to_cred(struct cred *new)
222 {
223         struct key *keyring;
224
225         if (new->thread_keyring)
226                 return 0;
227
228         keyring = keyring_alloc("_tid", new->uid, new->gid, new,
229                                 KEY_POS_ALL | KEY_USR_VIEW,
230                                 KEY_ALLOC_QUOTA_OVERRUN,
231                                 NULL, NULL);
232         if (IS_ERR(keyring))
233                 return PTR_ERR(keyring);
234
235         new->thread_keyring = keyring;
236         return 0;
237 }
238
239 /*
240  * Install a thread keyring to the current task if it didn't have one already.
241  *
242  * Return: 0 if a thread keyring is now present; -errno on failure.
243  */
244 static int install_thread_keyring(void)
245 {
246         struct cred *new;
247         int ret;
248
249         new = prepare_creds();
250         if (!new)
251                 return -ENOMEM;
252
253         ret = install_thread_keyring_to_cred(new);
254         if (ret < 0) {
255                 abort_creds(new);
256                 return ret;
257         }
258
259         return commit_creds(new);
260 }
261
262 /*
263  * Install a process keyring to the given credentials struct if it didn't have
264  * one already.  This is allowed to overrun the quota.
265  *
266  * Return: 0 if a process keyring is now present; -errno on failure.
267  */
268 int install_process_keyring_to_cred(struct cred *new)
269 {
270         struct key *keyring;
271
272         if (new->process_keyring)
273                 return 0;
274
275         keyring = keyring_alloc("_pid", new->uid, new->gid, new,
276                                 KEY_POS_ALL | KEY_USR_VIEW,
277                                 KEY_ALLOC_QUOTA_OVERRUN,
278                                 NULL, NULL);
279         if (IS_ERR(keyring))
280                 return PTR_ERR(keyring);
281
282         new->process_keyring = keyring;
283         return 0;
284 }
285
286 /*
287  * Install a process keyring to the current task if it didn't have one already.
288  *
289  * Return: 0 if a process keyring is now present; -errno on failure.
290  */
291 static int install_process_keyring(void)
292 {
293         struct cred *new;
294         int ret;
295
296         new = prepare_creds();
297         if (!new)
298                 return -ENOMEM;
299
300         ret = install_process_keyring_to_cred(new);
301         if (ret < 0) {
302                 abort_creds(new);
303                 return ret;
304         }
305
306         return commit_creds(new);
307 }
308
309 /*
310  * Install the given keyring as the session keyring of the given credentials
311  * struct, replacing the existing one if any.  If the given keyring is NULL,
312  * then install a new anonymous session keyring.
313  * @cred can not be in use by any task yet.
314  *
315  * Return: 0 on success; -errno on failure.
316  */
317 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
318 {
319         unsigned long flags;
320         struct key *old;
321
322         might_sleep();
323
324         /* create an empty session keyring */
325         if (!keyring) {
326                 flags = KEY_ALLOC_QUOTA_OVERRUN;
327                 if (cred->session_keyring)
328                         flags = KEY_ALLOC_IN_QUOTA;
329
330                 keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred,
331                                         KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
332                                         flags, NULL, NULL);
333                 if (IS_ERR(keyring))
334                         return PTR_ERR(keyring);
335         } else {
336                 __key_get(keyring);
337         }
338
339         /* install the keyring */
340         old = cred->session_keyring;
341         cred->session_keyring = keyring;
342
343         if (old)
344                 key_put(old);
345
346         return 0;
347 }
348
349 /*
350  * Install the given keyring as the session keyring of the current task,
351  * replacing the existing one if any.  If the given keyring is NULL, then
352  * install a new anonymous session keyring.
353  *
354  * Return: 0 on success; -errno on failure.
355  */
356 static int install_session_keyring(struct key *keyring)
357 {
358         struct cred *new;
359         int ret;
360
361         new = prepare_creds();
362         if (!new)
363                 return -ENOMEM;
364
365         ret = install_session_keyring_to_cred(new, keyring);
366         if (ret < 0) {
367                 abort_creds(new);
368                 return ret;
369         }
370
371         return commit_creds(new);
372 }
373
374 /*
375  * Handle the fsuid changing.
376  */
377 void key_fsuid_changed(struct cred *new_cred)
378 {
379         /* update the ownership of the thread keyring */
380         if (new_cred->thread_keyring) {
381                 down_write(&new_cred->thread_keyring->sem);
382                 new_cred->thread_keyring->uid = new_cred->fsuid;
383                 up_write(&new_cred->thread_keyring->sem);
384         }
385 }
386
387 /*
388  * Handle the fsgid changing.
389  */
390 void key_fsgid_changed(struct cred *new_cred)
391 {
392         /* update the ownership of the thread keyring */
393         if (new_cred->thread_keyring) {
394                 down_write(&new_cred->thread_keyring->sem);
395                 new_cred->thread_keyring->gid = new_cred->fsgid;
396                 up_write(&new_cred->thread_keyring->sem);
397         }
398 }
399
400 /*
401  * Search the process keyrings attached to the supplied cred for the first
402  * matching key under RCU conditions (the caller must be holding the RCU read
403  * lock).
404  *
405  * The search criteria are the type and the match function.  The description is
406  * given to the match function as a parameter, but doesn't otherwise influence
407  * the search.  Typically the match function will compare the description
408  * parameter to the key's description.
409  *
410  * This can only search keyrings that grant Search permission to the supplied
411  * credentials.  Keyrings linked to searched keyrings will also be searched if
412  * they grant Search permission too.  Keys can only be found if they grant
413  * Search permission to the credentials.
414  *
415  * Returns a pointer to the key with the key usage count incremented if
416  * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
417  * matched negative keys.
418  *
419  * In the case of a successful return, the possession attribute is set on the
420  * returned key reference.
421  */
422 key_ref_t search_cred_keyrings_rcu(struct keyring_search_context *ctx)
423 {
424         struct key *user_session;
425         key_ref_t key_ref, ret, err;
426         const struct cred *cred = ctx->cred;
427
428         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
429          * searchable, but we failed to find a key or we found a negative key;
430          * otherwise we want to return a sample error (probably -EACCES) if
431          * none of the keyrings were searchable
432          *
433          * in terms of priority: success > -ENOKEY > -EAGAIN > other error
434          */
435         key_ref = NULL;
436         ret = NULL;
437         err = ERR_PTR(-EAGAIN);
438
439         /* search the thread keyring first */
440         if (cred->thread_keyring) {
441                 key_ref = keyring_search_rcu(
442                         make_key_ref(cred->thread_keyring, 1), ctx);
443                 if (!IS_ERR(key_ref))
444                         goto found;
445
446                 switch (PTR_ERR(key_ref)) {
447                 case -EAGAIN: /* no key */
448                 case -ENOKEY: /* negative key */
449                         ret = key_ref;
450                         break;
451                 default:
452                         err = key_ref;
453                         break;
454                 }
455         }
456
457         /* search the process keyring second */
458         if (cred->process_keyring) {
459                 key_ref = keyring_search_rcu(
460                         make_key_ref(cred->process_keyring, 1), ctx);
461                 if (!IS_ERR(key_ref))
462                         goto found;
463
464                 switch (PTR_ERR(key_ref)) {
465                 case -EAGAIN: /* no key */
466                         if (ret)
467                                 break;
468                         fallthrough;
469                 case -ENOKEY: /* negative key */
470                         ret = key_ref;
471                         break;
472                 default:
473                         err = key_ref;
474                         break;
475                 }
476         }
477
478         /* search the session keyring */
479         if (cred->session_keyring) {
480                 key_ref = keyring_search_rcu(
481                         make_key_ref(cred->session_keyring, 1), ctx);
482
483                 if (!IS_ERR(key_ref))
484                         goto found;
485
486                 switch (PTR_ERR(key_ref)) {
487                 case -EAGAIN: /* no key */
488                         if (ret)
489                                 break;
490                         fallthrough;
491                 case -ENOKEY: /* negative key */
492                         ret = key_ref;
493                         break;
494                 default:
495                         err = key_ref;
496                         break;
497                 }
498         }
499         /* or search the user-session keyring */
500         else if ((user_session = get_user_session_keyring_rcu(cred))) {
501                 key_ref = keyring_search_rcu(make_key_ref(user_session, 1),
502                                              ctx);
503                 key_put(user_session);
504
505                 if (!IS_ERR(key_ref))
506                         goto found;
507
508                 switch (PTR_ERR(key_ref)) {
509                 case -EAGAIN: /* no key */
510                         if (ret)
511                                 break;
512                         fallthrough;
513                 case -ENOKEY: /* negative key */
514                         ret = key_ref;
515                         break;
516                 default:
517                         err = key_ref;
518                         break;
519                 }
520         }
521
522         /* no key - decide on the error we're going to go for */
523         key_ref = ret ? ret : err;
524
525 found:
526         return key_ref;
527 }
528
529 /*
530  * Search the process keyrings attached to the supplied cred for the first
531  * matching key in the manner of search_my_process_keyrings(), but also search
532  * the keys attached to the assumed authorisation key using its credentials if
533  * one is available.
534  *
535  * The caller must be holding the RCU read lock.
536  *
537  * Return same as search_cred_keyrings_rcu().
538  */
539 key_ref_t search_process_keyrings_rcu(struct keyring_search_context *ctx)
540 {
541         struct request_key_auth *rka;
542         key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
543
544         key_ref = search_cred_keyrings_rcu(ctx);
545         if (!IS_ERR(key_ref))
546                 goto found;
547         err = key_ref;
548
549         /* if this process has an instantiation authorisation key, then we also
550          * search the keyrings of the process mentioned there
551          * - we don't permit access to request_key auth keys via this method
552          */
553         if (ctx->cred->request_key_auth &&
554             ctx->cred == current_cred() &&
555             ctx->index_key.type != &key_type_request_key_auth
556             ) {
557                 const struct cred *cred = ctx->cred;
558
559                 if (key_validate(cred->request_key_auth) == 0) {
560                         rka = ctx->cred->request_key_auth->payload.data[0];
561
562                         //// was search_process_keyrings() [ie. recursive]
563                         ctx->cred = rka->cred;
564                         key_ref = search_cred_keyrings_rcu(ctx);
565                         ctx->cred = cred;
566
567                         if (!IS_ERR(key_ref))
568                                 goto found;
569                         ret = key_ref;
570                 }
571         }
572
573         /* no key - decide on the error we're going to go for */
574         if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
575                 key_ref = ERR_PTR(-ENOKEY);
576         else if (err == ERR_PTR(-EACCES))
577                 key_ref = ret;
578         else
579                 key_ref = err;
580
581 found:
582         return key_ref;
583 }
584 /*
585  * See if the key we're looking at is the target key.
586  */
587 bool lookup_user_key_possessed(const struct key *key,
588                                const struct key_match_data *match_data)
589 {
590         return key == match_data->raw_data;
591 }
592
593 /*
594  * Look up a key ID given us by userspace with a given permissions mask to get
595  * the key it refers to.
596  *
597  * Flags can be passed to request that special keyrings be created if referred
598  * to directly, to permit partially constructed keys to be found and to skip
599  * validity and permission checks on the found key.
600  *
601  * Returns a pointer to the key with an incremented usage count if successful;
602  * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
603  * to a key or the best found key was a negative key; -EKEYREVOKED or
604  * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
605  * found key doesn't grant the requested permit or the LSM denied access to it;
606  * or -ENOMEM if a special keyring couldn't be created.
607  *
608  * In the case of a successful return, the possession attribute is set on the
609  * returned key reference.
610  */
611 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
612                           enum key_need_perm need_perm)
613 {
614         struct keyring_search_context ctx = {
615                 .match_data.cmp         = lookup_user_key_possessed,
616                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
617                 .flags                  = (KEYRING_SEARCH_NO_STATE_CHECK |
618                                            KEYRING_SEARCH_RECURSE),
619         };
620         struct request_key_auth *rka;
621         struct key *key, *user_session;
622         key_ref_t key_ref, skey_ref;
623         int ret;
624
625 try_again:
626         ctx.cred = get_current_cred();
627         key_ref = ERR_PTR(-ENOKEY);
628
629         switch (id) {
630         case KEY_SPEC_THREAD_KEYRING:
631                 if (!ctx.cred->thread_keyring) {
632                         if (!(lflags & KEY_LOOKUP_CREATE))
633                                 goto error;
634
635                         ret = install_thread_keyring();
636                         if (ret < 0) {
637                                 key_ref = ERR_PTR(ret);
638                                 goto error;
639                         }
640                         goto reget_creds;
641                 }
642
643                 key = ctx.cred->thread_keyring;
644                 __key_get(key);
645                 key_ref = make_key_ref(key, 1);
646                 break;
647
648         case KEY_SPEC_PROCESS_KEYRING:
649                 if (!ctx.cred->process_keyring) {
650                         if (!(lflags & KEY_LOOKUP_CREATE))
651                                 goto error;
652
653                         ret = install_process_keyring();
654                         if (ret < 0) {
655                                 key_ref = ERR_PTR(ret);
656                                 goto error;
657                         }
658                         goto reget_creds;
659                 }
660
661                 key = ctx.cred->process_keyring;
662                 __key_get(key);
663                 key_ref = make_key_ref(key, 1);
664                 break;
665
666         case KEY_SPEC_SESSION_KEYRING:
667                 if (!ctx.cred->session_keyring) {
668                         /* always install a session keyring upon access if one
669                          * doesn't exist yet */
670                         ret = look_up_user_keyrings(NULL, &user_session);
671                         if (ret < 0)
672                                 goto error;
673                         if (lflags & KEY_LOOKUP_CREATE)
674                                 ret = join_session_keyring(NULL);
675                         else
676                                 ret = install_session_keyring(user_session);
677
678                         key_put(user_session);
679                         if (ret < 0)
680                                 goto error;
681                         goto reget_creds;
682                 } else if (test_bit(KEY_FLAG_UID_KEYRING,
683                                     &ctx.cred->session_keyring->flags) &&
684                            lflags & KEY_LOOKUP_CREATE) {
685                         ret = join_session_keyring(NULL);
686                         if (ret < 0)
687                                 goto error;
688                         goto reget_creds;
689                 }
690
691                 key = ctx.cred->session_keyring;
692                 __key_get(key);
693                 key_ref = make_key_ref(key, 1);
694                 break;
695
696         case KEY_SPEC_USER_KEYRING:
697                 ret = look_up_user_keyrings(&key, NULL);
698                 if (ret < 0)
699                         goto error;
700                 key_ref = make_key_ref(key, 1);
701                 break;
702
703         case KEY_SPEC_USER_SESSION_KEYRING:
704                 ret = look_up_user_keyrings(NULL, &key);
705                 if (ret < 0)
706                         goto error;
707                 key_ref = make_key_ref(key, 1);
708                 break;
709
710         case KEY_SPEC_GROUP_KEYRING:
711                 /* group keyrings are not yet supported */
712                 key_ref = ERR_PTR(-EINVAL);
713                 goto error;
714
715         case KEY_SPEC_REQKEY_AUTH_KEY:
716                 key = ctx.cred->request_key_auth;
717                 if (!key)
718                         goto error;
719
720                 __key_get(key);
721                 key_ref = make_key_ref(key, 1);
722                 break;
723
724         case KEY_SPEC_REQUESTOR_KEYRING:
725                 if (!ctx.cred->request_key_auth)
726                         goto error;
727
728                 down_read(&ctx.cred->request_key_auth->sem);
729                 if (test_bit(KEY_FLAG_REVOKED,
730                              &ctx.cred->request_key_auth->flags)) {
731                         key_ref = ERR_PTR(-EKEYREVOKED);
732                         key = NULL;
733                 } else {
734                         rka = ctx.cred->request_key_auth->payload.data[0];
735                         key = rka->dest_keyring;
736                         __key_get(key);
737                 }
738                 up_read(&ctx.cred->request_key_auth->sem);
739                 if (!key)
740                         goto error;
741                 key_ref = make_key_ref(key, 1);
742                 break;
743
744         default:
745                 key_ref = ERR_PTR(-EINVAL);
746                 if (id < 1)
747                         goto error;
748
749                 key = key_lookup(id);
750                 if (IS_ERR(key)) {
751                         key_ref = ERR_CAST(key);
752                         goto error;
753                 }
754
755                 key_ref = make_key_ref(key, 0);
756
757                 /* check to see if we possess the key */
758                 ctx.index_key                   = key->index_key;
759                 ctx.match_data.raw_data         = key;
760                 kdebug("check possessed");
761                 rcu_read_lock();
762                 skey_ref = search_process_keyrings_rcu(&ctx);
763                 rcu_read_unlock();
764                 kdebug("possessed=%p", skey_ref);
765
766                 if (!IS_ERR(skey_ref)) {
767                         key_put(key);
768                         key_ref = skey_ref;
769                 }
770
771                 break;
772         }
773
774         /* unlink does not use the nominated key in any way, so can skip all
775          * the permission checks as it is only concerned with the keyring */
776         if (need_perm != KEY_NEED_UNLINK) {
777                 if (!(lflags & KEY_LOOKUP_PARTIAL)) {
778                         ret = wait_for_key_construction(key, true);
779                         switch (ret) {
780                         case -ERESTARTSYS:
781                                 goto invalid_key;
782                         default:
783                                 if (need_perm != KEY_AUTHTOKEN_OVERRIDE &&
784                                     need_perm != KEY_DEFER_PERM_CHECK)
785                                         goto invalid_key;
786                                 break;
787                         case 0:
788                                 break;
789                         }
790                 } else if (need_perm != KEY_DEFER_PERM_CHECK) {
791                         ret = key_validate(key);
792                         if (ret < 0)
793                                 goto invalid_key;
794                 }
795
796                 ret = -EIO;
797                 if (!(lflags & KEY_LOOKUP_PARTIAL) &&
798                     key_read_state(key) == KEY_IS_UNINSTANTIATED)
799                         goto invalid_key;
800         }
801
802         /* check the permissions */
803         ret = key_task_permission(key_ref, ctx.cred, need_perm);
804         if (ret < 0)
805                 goto invalid_key;
806
807         key->last_used_at = ktime_get_real_seconds();
808
809 error:
810         put_cred(ctx.cred);
811         return key_ref;
812
813 invalid_key:
814         key_ref_put(key_ref);
815         key_ref = ERR_PTR(ret);
816         goto error;
817
818         /* if we attempted to install a keyring, then it may have caused new
819          * creds to be installed */
820 reget_creds:
821         put_cred(ctx.cred);
822         goto try_again;
823 }
824 EXPORT_SYMBOL(lookup_user_key);
825
826 /*
827  * Join the named keyring as the session keyring if possible else attempt to
828  * create a new one of that name and join that.
829  *
830  * If the name is NULL, an empty anonymous keyring will be installed as the
831  * session keyring.
832  *
833  * Named session keyrings are joined with a semaphore held to prevent the
834  * keyrings from going away whilst the attempt is made to going them and also
835  * to prevent a race in creating compatible session keyrings.
836  */
837 long join_session_keyring(const char *name)
838 {
839         const struct cred *old;
840         struct cred *new;
841         struct key *keyring;
842         long ret, serial;
843
844         new = prepare_creds();
845         if (!new)
846                 return -ENOMEM;
847         old = current_cred();
848
849         /* if no name is provided, install an anonymous keyring */
850         if (!name) {
851                 ret = install_session_keyring_to_cred(new, NULL);
852                 if (ret < 0)
853                         goto error;
854
855                 serial = new->session_keyring->serial;
856                 ret = commit_creds(new);
857                 if (ret == 0)
858                         ret = serial;
859                 goto okay;
860         }
861
862         /* allow the user to join or create a named keyring */
863         mutex_lock(&key_session_mutex);
864
865         /* look for an existing keyring of this name */
866         keyring = find_keyring_by_name(name, false);
867         if (PTR_ERR(keyring) == -ENOKEY) {
868                 /* not found - try and create a new one */
869                 keyring = keyring_alloc(
870                         name, old->uid, old->gid, old,
871                         KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_LINK,
872                         KEY_ALLOC_IN_QUOTA, NULL, NULL);
873                 if (IS_ERR(keyring)) {
874                         ret = PTR_ERR(keyring);
875                         goto error2;
876                 }
877         } else if (IS_ERR(keyring)) {
878                 ret = PTR_ERR(keyring);
879                 goto error2;
880         } else if (keyring == new->session_keyring) {
881                 ret = 0;
882                 goto error3;
883         }
884
885         /* we've got a keyring - now to install it */
886         ret = install_session_keyring_to_cred(new, keyring);
887         if (ret < 0)
888                 goto error3;
889
890         commit_creds(new);
891         mutex_unlock(&key_session_mutex);
892
893         ret = keyring->serial;
894         key_put(keyring);
895 okay:
896         return ret;
897
898 error3:
899         key_put(keyring);
900 error2:
901         mutex_unlock(&key_session_mutex);
902 error:
903         abort_creds(new);
904         return ret;
905 }
906
907 /*
908  * Replace a process's session keyring on behalf of one of its children when
909  * the target  process is about to resume userspace execution.
910  */
911 void key_change_session_keyring(struct callback_head *twork)
912 {
913         const struct cred *old = current_cred();
914         struct cred *new = container_of(twork, struct cred, rcu);
915
916         if (unlikely(current->flags & PF_EXITING)) {
917                 put_cred(new);
918                 return;
919         }
920
921         /* If get_ucounts fails more bits are needed in the refcount */
922         if (unlikely(!get_ucounts(old->ucounts))) {
923                 WARN_ONCE(1, "In %s get_ucounts failed\n", __func__);
924                 put_cred(new);
925                 return;
926         }
927
928         new->  uid      = old->  uid;
929         new-> euid      = old-> euid;
930         new-> suid      = old-> suid;
931         new->fsuid      = old->fsuid;
932         new->  gid      = old->  gid;
933         new-> egid      = old-> egid;
934         new-> sgid      = old-> sgid;
935         new->fsgid      = old->fsgid;
936         new->user       = get_uid(old->user);
937         new->ucounts    = old->ucounts;
938         new->user_ns    = get_user_ns(old->user_ns);
939         new->group_info = get_group_info(old->group_info);
940
941         new->securebits = old->securebits;
942         new->cap_inheritable    = old->cap_inheritable;
943         new->cap_permitted      = old->cap_permitted;
944         new->cap_effective      = old->cap_effective;
945         new->cap_ambient        = old->cap_ambient;
946         new->cap_bset           = old->cap_bset;
947
948         new->jit_keyring        = old->jit_keyring;
949         new->thread_keyring     = key_get(old->thread_keyring);
950         new->process_keyring    = key_get(old->process_keyring);
951
952         security_transfer_creds(new, old);
953
954         commit_creds(new);
955 }
956
957 /*
958  * Make sure that root's user and user-session keyrings exist.
959  */
960 static int __init init_root_keyring(void)
961 {
962         return look_up_user_keyrings(NULL, NULL);
963 }
964
965 late_initcall(init_root_keyring);