[PATCH] Destruction of failed keyring oopses
[linux-2.6.git] / security / keys / keyring.c
1 /* keyring.c: keyring handling
2  *
3  * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/slab.h>
16 #include <linux/seq_file.h>
17 #include <linux/err.h>
18 #include <asm/uaccess.h>
19 #include "internal.h"
20
21 /*
22  * when plumbing the depths of the key tree, this sets a hard limit set on how
23  * deep we're willing to go
24  */
25 #define KEYRING_SEARCH_MAX_DEPTH 6
26
27 /*
28  * we keep all named keyrings in a hash to speed looking them up
29  */
30 #define KEYRING_NAME_HASH_SIZE  (1 << 5)
31
32 static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
33 static DEFINE_RWLOCK(keyring_name_lock);
34
35 static inline unsigned keyring_hash(const char *desc)
36 {
37         unsigned bucket = 0;
38
39         for (; *desc; desc++)
40                 bucket += (unsigned char) *desc;
41
42         return bucket & (KEYRING_NAME_HASH_SIZE - 1);
43 }
44
45 /*
46  * the keyring type definition
47  */
48 static int keyring_instantiate(struct key *keyring,
49                                const void *data, size_t datalen);
50 static int keyring_duplicate(struct key *keyring, const struct key *source);
51 static int keyring_match(const struct key *keyring, const void *criterion);
52 static void keyring_destroy(struct key *keyring);
53 static void keyring_describe(const struct key *keyring, struct seq_file *m);
54 static long keyring_read(const struct key *keyring,
55                          char __user *buffer, size_t buflen);
56
57 struct key_type key_type_keyring = {
58         .name           = "keyring",
59         .def_datalen    = sizeof(struct keyring_list),
60         .instantiate    = keyring_instantiate,
61         .duplicate      = keyring_duplicate,
62         .match          = keyring_match,
63         .destroy        = keyring_destroy,
64         .describe       = keyring_describe,
65         .read           = keyring_read,
66 };
67
68 /*
69  * semaphore to serialise link/link calls to prevent two link calls in parallel
70  * introducing a cycle
71  */
72 DECLARE_RWSEM(keyring_serialise_link_sem);
73
74 /*****************************************************************************/
75 /*
76  * publish the name of a keyring so that it can be found by name (if it has
77  * one)
78  */
79 void keyring_publish_name(struct key *keyring)
80 {
81         int bucket;
82
83         if (keyring->description) {
84                 bucket = keyring_hash(keyring->description);
85
86                 write_lock(&keyring_name_lock);
87
88                 if (!keyring_name_hash[bucket].next)
89                         INIT_LIST_HEAD(&keyring_name_hash[bucket]);
90
91                 list_add_tail(&keyring->type_data.link,
92                               &keyring_name_hash[bucket]);
93
94                 write_unlock(&keyring_name_lock);
95         }
96
97 } /* end keyring_publish_name() */
98
99 /*****************************************************************************/
100 /*
101  * initialise a keyring
102  * - we object if we were given any data
103  */
104 static int keyring_instantiate(struct key *keyring,
105                                const void *data, size_t datalen)
106 {
107         int ret;
108
109         ret = -EINVAL;
110         if (datalen == 0) {
111                 /* make the keyring available by name if it has one */
112                 keyring_publish_name(keyring);
113                 ret = 0;
114         }
115
116         return ret;
117
118 } /* end keyring_instantiate() */
119
120 /*****************************************************************************/
121 /*
122  * duplicate the list of subscribed keys from a source keyring into this one
123  */
124 static int keyring_duplicate(struct key *keyring, const struct key *source)
125 {
126         struct keyring_list *sklist, *klist;
127         unsigned max;
128         size_t size;
129         int loop, ret;
130
131         const unsigned limit =
132                 (PAGE_SIZE - sizeof(*klist)) / sizeof(struct key *);
133
134         ret = 0;
135
136         /* find out how many keys are currently linked */
137         rcu_read_lock();
138         sklist = rcu_dereference(source->payload.subscriptions);
139         max = 0;
140         if (sklist)
141                 max = sklist->nkeys;
142         rcu_read_unlock();
143
144         /* allocate a new payload and stuff load with key links */
145         if (max > 0) {
146                 BUG_ON(max > limit);
147
148                 max = (max + 3) & ~3;
149                 if (max > limit)
150                         max = limit;
151
152                 ret = -ENOMEM;
153                 size = sizeof(*klist) + sizeof(struct key *) * max;
154                 klist = kmalloc(size, GFP_KERNEL);
155                 if (!klist)
156                         goto error;
157
158                 /* set links */
159                 rcu_read_lock();
160                 sklist = rcu_dereference(source->payload.subscriptions);
161
162                 klist->maxkeys = max;
163                 klist->nkeys = sklist->nkeys;
164                 memcpy(klist->keys,
165                        sklist->keys,
166                        sklist->nkeys * sizeof(struct key *));
167
168                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
169                         atomic_inc(&klist->keys[loop]->usage);
170
171                 rcu_read_unlock();
172
173                 rcu_assign_pointer(keyring->payload.subscriptions, klist);
174                 ret = 0;
175         }
176
177  error:
178         return ret;
179
180 } /* end keyring_duplicate() */
181
182 /*****************************************************************************/
183 /*
184  * match keyrings on their name
185  */
186 static int keyring_match(const struct key *keyring, const void *description)
187 {
188         return keyring->description &&
189                 strcmp(keyring->description, description) == 0;
190
191 } /* end keyring_match() */
192
193 /*****************************************************************************/
194 /*
195  * dispose of the data dangling from the corpse of a keyring
196  */
197 static void keyring_destroy(struct key *keyring)
198 {
199         struct keyring_list *klist;
200         int loop;
201
202         if (keyring->description) {
203                 write_lock(&keyring_name_lock);
204
205                 if (keyring->type_data.link.next != NULL &&
206                     !list_empty(&keyring->type_data.link))
207                         list_del(&keyring->type_data.link);
208
209                 write_unlock(&keyring_name_lock);
210         }
211
212         klist = rcu_dereference(keyring->payload.subscriptions);
213         if (klist) {
214                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
215                         key_put(klist->keys[loop]);
216                 kfree(klist);
217         }
218
219 } /* end keyring_destroy() */
220
221 /*****************************************************************************/
222 /*
223  * describe the keyring
224  */
225 static void keyring_describe(const struct key *keyring, struct seq_file *m)
226 {
227         struct keyring_list *klist;
228
229         if (keyring->description) {
230                 seq_puts(m, keyring->description);
231         }
232         else {
233                 seq_puts(m, "[anon]");
234         }
235
236         rcu_read_lock();
237         klist = rcu_dereference(keyring->payload.subscriptions);
238         if (klist)
239                 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
240         else
241                 seq_puts(m, ": empty");
242         rcu_read_unlock();
243
244 } /* end keyring_describe() */
245
246 /*****************************************************************************/
247 /*
248  * read a list of key IDs from the keyring's contents
249  * - the keyring's semaphore is read-locked
250  */
251 static long keyring_read(const struct key *keyring,
252                          char __user *buffer, size_t buflen)
253 {
254         struct keyring_list *klist;
255         struct key *key;
256         size_t qty, tmp;
257         int loop, ret;
258
259         ret = 0;
260         klist = rcu_dereference(keyring->payload.subscriptions);
261
262         if (klist) {
263                 /* calculate how much data we could return */
264                 qty = klist->nkeys * sizeof(key_serial_t);
265
266                 if (buffer && buflen > 0) {
267                         if (buflen > qty)
268                                 buflen = qty;
269
270                         /* copy the IDs of the subscribed keys into the
271                          * buffer */
272                         ret = -EFAULT;
273
274                         for (loop = 0; loop < klist->nkeys; loop++) {
275                                 key = klist->keys[loop];
276
277                                 tmp = sizeof(key_serial_t);
278                                 if (tmp > buflen)
279                                         tmp = buflen;
280
281                                 if (copy_to_user(buffer,
282                                                  &key->serial,
283                                                  tmp) != 0)
284                                         goto error;
285
286                                 buflen -= tmp;
287                                 if (buflen == 0)
288                                         break;
289                                 buffer += tmp;
290                         }
291                 }
292
293                 ret = qty;
294         }
295
296  error:
297         return ret;
298
299 } /* end keyring_read() */
300
301 /*****************************************************************************/
302 /*
303  * allocate a keyring and link into the destination keyring
304  */
305 struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
306                           int not_in_quota, struct key *dest)
307 {
308         struct key *keyring;
309         int ret;
310
311         keyring = key_alloc(&key_type_keyring, description,
312                             uid, gid, KEY_USR_ALL, not_in_quota);
313
314         if (!IS_ERR(keyring)) {
315                 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
316                 if (ret < 0) {
317                         key_put(keyring);
318                         keyring = ERR_PTR(ret);
319                 }
320         }
321
322         return keyring;
323
324 } /* end keyring_alloc() */
325
326 /*****************************************************************************/
327 /*
328  * search the supplied keyring tree for a key that matches the criterion
329  * - perform a breadth-then-depth search up to the prescribed limit
330  * - we only find keys on which we have search permission
331  * - we use the supplied match function to see if the description (or other
332  *   feature of interest) matches
333  * - we rely on RCU to prevent the keyring lists from disappearing on us
334  * - we return -EAGAIN if we didn't find any matching key
335  * - we return -ENOKEY if we only found negative matching keys
336  */
337 struct key *keyring_search_aux(struct key *keyring,
338                                struct task_struct *context,
339                                struct key_type *type,
340                                const void *description,
341                                key_match_func_t match)
342 {
343         struct {
344                 struct keyring_list *keylist;
345                 int kix;
346         } stack[KEYRING_SEARCH_MAX_DEPTH];
347
348         struct keyring_list *keylist;
349         struct timespec now;
350         struct key *key;
351         long err;
352         int sp, kix;
353
354         key_check(keyring);
355
356         rcu_read_lock();
357
358         /* top keyring must have search permission to begin the search */
359         key = ERR_PTR(-EACCES);
360         if (!key_task_permission(keyring, context, KEY_SEARCH))
361                 goto error;
362
363         key = ERR_PTR(-ENOTDIR);
364         if (keyring->type != &key_type_keyring)
365                 goto error;
366
367         now = current_kernel_time();
368         err = -EAGAIN;
369         sp = 0;
370
371         /* start processing a new keyring */
372  descend:
373         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
374                 goto not_this_keyring;
375
376         keylist = rcu_dereference(keyring->payload.subscriptions);
377         if (!keylist)
378                 goto not_this_keyring;
379
380         /* iterate through the keys in this keyring first */
381         for (kix = 0; kix < keylist->nkeys; kix++) {
382                 key = keylist->keys[kix];
383
384                 /* ignore keys not of this type */
385                 if (key->type != type)
386                         continue;
387
388                 /* skip revoked keys and expired keys */
389                 if (test_bit(KEY_FLAG_REVOKED, &key->flags))
390                         continue;
391
392                 if (key->expiry && now.tv_sec >= key->expiry)
393                         continue;
394
395                 /* keys that don't match */
396                 if (!match(key, description))
397                         continue;
398
399                 /* key must have search permissions */
400                 if (!key_task_permission(key, context, KEY_SEARCH))
401                         continue;
402
403                 /* we set a different error code if we find a negative key */
404                 if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
405                         err = -ENOKEY;
406                         continue;
407                 }
408
409                 goto found;
410         }
411
412         /* search through the keyrings nested in this one */
413         kix = 0;
414  ascend:
415         for (; kix < keylist->nkeys; kix++) {
416                 key = keylist->keys[kix];
417                 if (key->type != &key_type_keyring)
418                         continue;
419
420                 /* recursively search nested keyrings
421                  * - only search keyrings for which we have search permission
422                  */
423                 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
424                         continue;
425
426                 if (!key_task_permission(key, context, KEY_SEARCH))
427                         continue;
428
429                 /* stack the current position */
430                 stack[sp].keylist = keylist;
431                 stack[sp].kix = kix;
432                 sp++;
433
434                 /* begin again with the new keyring */
435                 keyring = key;
436                 goto descend;
437         }
438
439         /* the keyring we're looking at was disqualified or didn't contain a
440          * matching key */
441  not_this_keyring:
442         if (sp > 0) {
443                 /* resume the processing of a keyring higher up in the tree */
444                 sp--;
445                 keylist = stack[sp].keylist;
446                 kix = stack[sp].kix + 1;
447                 goto ascend;
448         }
449
450         key = ERR_PTR(err);
451         goto error;
452
453         /* we found a viable match */
454  found:
455         atomic_inc(&key->usage);
456         key_check(key);
457  error:
458         rcu_read_unlock();
459         return key;
460
461 } /* end keyring_search_aux() */
462
463 /*****************************************************************************/
464 /*
465  * search the supplied keyring tree for a key that matches the criterion
466  * - perform a breadth-then-depth search up to the prescribed limit
467  * - we only find keys on which we have search permission
468  * - we readlock the keyrings as we search down the tree
469  * - we return -EAGAIN if we didn't find any matching key
470  * - we return -ENOKEY if we only found negative matching keys
471  */
472 struct key *keyring_search(struct key *keyring,
473                            struct key_type *type,
474                            const char *description)
475 {
476         if (!type->match)
477                 return ERR_PTR(-ENOKEY);
478
479         return keyring_search_aux(keyring, current,
480                                   type, description, type->match);
481
482 } /* end keyring_search() */
483
484 EXPORT_SYMBOL(keyring_search);
485
486 /*****************************************************************************/
487 /*
488  * search the given keyring only (no recursion)
489  * - keyring must be locked by caller
490  */
491 struct key *__keyring_search_one(struct key *keyring,
492                                  const struct key_type *ktype,
493                                  const char *description,
494                                  key_perm_t perm)
495 {
496         struct keyring_list *klist;
497         struct key *key;
498         int loop;
499
500         rcu_read_lock();
501
502         klist = rcu_dereference(keyring->payload.subscriptions);
503         if (klist) {
504                 for (loop = 0; loop < klist->nkeys; loop++) {
505                         key = klist->keys[loop];
506
507                         if (key->type == ktype &&
508                             (!key->type->match ||
509                              key->type->match(key, description)) &&
510                             key_permission(key, perm) &&
511                             !test_bit(KEY_FLAG_REVOKED, &key->flags)
512                             )
513                                 goto found;
514                 }
515         }
516
517         key = ERR_PTR(-ENOKEY);
518         goto error;
519
520  found:
521         atomic_inc(&key->usage);
522  error:
523         rcu_read_unlock();
524         return key;
525
526 } /* end __keyring_search_one() */
527
528 /*****************************************************************************/
529 /*
530  * search for an instantiation authorisation key matching a target key
531  * - the RCU read lock must be held by the caller
532  * - a target_id of zero specifies any valid token
533  */
534 struct key *keyring_search_instkey(struct key *keyring,
535                                    key_serial_t target_id)
536 {
537         struct request_key_auth *rka;
538         struct keyring_list *klist;
539         struct key *instkey;
540         int loop;
541
542         klist = rcu_dereference(keyring->payload.subscriptions);
543         if (klist) {
544                 for (loop = 0; loop < klist->nkeys; loop++) {
545                         instkey = klist->keys[loop];
546
547                         if (instkey->type != &key_type_request_key_auth)
548                                 continue;
549
550                         rka = instkey->payload.data;
551                         if (target_id && rka->target_key->serial != target_id)
552                                 continue;
553
554                         /* the auth key is revoked during instantiation */
555                         if (!test_bit(KEY_FLAG_REVOKED, &instkey->flags))
556                                 goto found;
557
558                         instkey = ERR_PTR(-EKEYREVOKED);
559                         goto error;
560                 }
561         }
562
563         instkey = ERR_PTR(-EACCES);
564         goto error;
565
566 found:
567         atomic_inc(&instkey->usage);
568 error:
569         return instkey;
570
571 } /* end keyring_search_instkey() */
572
573 /*****************************************************************************/
574 /*
575  * find a keyring with the specified name
576  * - all named keyrings are searched
577  * - only find keyrings with search permission for the process
578  * - only find keyrings with a serial number greater than the one specified
579  */
580 struct key *find_keyring_by_name(const char *name, key_serial_t bound)
581 {
582         struct key *keyring;
583         int bucket;
584
585         keyring = ERR_PTR(-EINVAL);
586         if (!name)
587                 goto error;
588
589         bucket = keyring_hash(name);
590
591         read_lock(&keyring_name_lock);
592
593         if (keyring_name_hash[bucket].next) {
594                 /* search this hash bucket for a keyring with a matching name
595                  * that's readable and that hasn't been revoked */
596                 list_for_each_entry(keyring,
597                                     &keyring_name_hash[bucket],
598                                     type_data.link
599                                     ) {
600                         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
601                                 continue;
602
603                         if (strcmp(keyring->description, name) != 0)
604                                 continue;
605
606                         if (!key_permission(keyring, KEY_SEARCH))
607                                 continue;
608
609                         /* found a potential candidate, but we still need to
610                          * check the serial number */
611                         if (keyring->serial <= bound)
612                                 continue;
613
614                         /* we've got a match */
615                         atomic_inc(&keyring->usage);
616                         read_unlock(&keyring_name_lock);
617                         goto error;
618                 }
619         }
620
621         read_unlock(&keyring_name_lock);
622         keyring = ERR_PTR(-ENOKEY);
623
624  error:
625         return keyring;
626
627 } /* end find_keyring_by_name() */
628
629 /*****************************************************************************/
630 /*
631  * see if a cycle will will be created by inserting acyclic tree B in acyclic
632  * tree A at the topmost level (ie: as a direct child of A)
633  * - since we are adding B to A at the top level, checking for cycles should
634  *   just be a matter of seeing if node A is somewhere in tree B
635  */
636 static int keyring_detect_cycle(struct key *A, struct key *B)
637 {
638         struct {
639                 struct keyring_list *keylist;
640                 int kix;
641         } stack[KEYRING_SEARCH_MAX_DEPTH];
642
643         struct keyring_list *keylist;
644         struct key *subtree, *key;
645         int sp, kix, ret;
646
647         rcu_read_lock();
648
649         ret = -EDEADLK;
650         if (A == B)
651                 goto cycle_detected;
652
653         subtree = B;
654         sp = 0;
655
656         /* start processing a new keyring */
657  descend:
658         if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
659                 goto not_this_keyring;
660
661         keylist = rcu_dereference(subtree->payload.subscriptions);
662         if (!keylist)
663                 goto not_this_keyring;
664         kix = 0;
665
666  ascend:
667         /* iterate through the remaining keys in this keyring */
668         for (; kix < keylist->nkeys; kix++) {
669                 key = keylist->keys[kix];
670
671                 if (key == A)
672                         goto cycle_detected;
673
674                 /* recursively check nested keyrings */
675                 if (key->type == &key_type_keyring) {
676                         if (sp >= KEYRING_SEARCH_MAX_DEPTH)
677                                 goto too_deep;
678
679                         /* stack the current position */
680                         stack[sp].keylist = keylist;
681                         stack[sp].kix = kix;
682                         sp++;
683
684                         /* begin again with the new keyring */
685                         subtree = key;
686                         goto descend;
687                 }
688         }
689
690         /* the keyring we're looking at was disqualified or didn't contain a
691          * matching key */
692  not_this_keyring:
693         if (sp > 0) {
694                 /* resume the checking of a keyring higher up in the tree */
695                 sp--;
696                 keylist = stack[sp].keylist;
697                 kix = stack[sp].kix + 1;
698                 goto ascend;
699         }
700
701         ret = 0; /* no cycles detected */
702
703  error:
704         rcu_read_unlock();
705         return ret;
706
707  too_deep:
708         ret = -ELOOP;
709         goto error;
710
711  cycle_detected:
712         ret = -EDEADLK;
713         goto error;
714
715 } /* end keyring_detect_cycle() */
716
717 /*****************************************************************************/
718 /*
719  * dispose of a keyring list after the RCU grace period
720  */
721 static void keyring_link_rcu_disposal(struct rcu_head *rcu)
722 {
723         struct keyring_list *klist =
724                 container_of(rcu, struct keyring_list, rcu);
725
726         kfree(klist);
727
728 } /* end keyring_link_rcu_disposal() */
729
730 /*****************************************************************************/
731 /*
732  * link a key into to a keyring
733  * - must be called with the keyring's semaphore write-locked
734  */
735 int __key_link(struct key *keyring, struct key *key)
736 {
737         struct keyring_list *klist, *nklist;
738         unsigned max;
739         size_t size;
740         int ret;
741
742         ret = -EKEYREVOKED;
743         if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
744                 goto error;
745
746         ret = -ENOTDIR;
747         if (keyring->type != &key_type_keyring)
748                 goto error;
749
750         /* serialise link/link calls to prevent parallel calls causing a
751          * cycle when applied to two keyring in opposite orders */
752         down_write(&keyring_serialise_link_sem);
753
754         /* check that we aren't going to create a cycle adding one keyring to
755          * another */
756         if (key->type == &key_type_keyring) {
757                 ret = keyring_detect_cycle(keyring, key);
758                 if (ret < 0)
759                         goto error2;
760         }
761
762         /* check that we aren't going to overrun the user's quota */
763         ret = key_payload_reserve(keyring,
764                                   keyring->datalen + KEYQUOTA_LINK_BYTES);
765         if (ret < 0)
766                 goto error2;
767
768         klist = keyring->payload.subscriptions;
769
770         if (klist && klist->nkeys < klist->maxkeys) {
771                 /* there's sufficient slack space to add directly */
772                 atomic_inc(&key->usage);
773
774                 klist->keys[klist->nkeys] = key;
775                 smp_wmb();
776                 klist->nkeys++;
777                 smp_wmb();
778
779                 ret = 0;
780         }
781         else {
782                 /* grow the key list */
783                 max = 4;
784                 if (klist)
785                         max += klist->maxkeys;
786
787                 ret = -ENFILE;
788                 if (max > 65535)
789                         goto error3;
790                 size = sizeof(*klist) + sizeof(struct key *) * max;
791                 if (size > PAGE_SIZE)
792                         goto error3;
793
794                 ret = -ENOMEM;
795                 nklist = kmalloc(size, GFP_KERNEL);
796                 if (!nklist)
797                         goto error3;
798                 nklist->maxkeys = max;
799                 nklist->nkeys = 0;
800
801                 if (klist) {
802                         nklist->nkeys = klist->nkeys;
803                         memcpy(nklist->keys,
804                                klist->keys,
805                                sizeof(struct key *) * klist->nkeys);
806                 }
807
808                 /* add the key into the new space */
809                 atomic_inc(&key->usage);
810                 nklist->keys[nklist->nkeys++] = key;
811
812                 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
813
814                 /* dispose of the old keyring list */
815                 if (klist)
816                         call_rcu(&klist->rcu, keyring_link_rcu_disposal);
817
818                 ret = 0;
819         }
820
821  error2:
822         up_write(&keyring_serialise_link_sem);
823  error:
824         return ret;
825
826  error3:
827         /* undo the quota changes */
828         key_payload_reserve(keyring,
829                             keyring->datalen - KEYQUOTA_LINK_BYTES);
830         goto error2;
831
832 } /* end __key_link() */
833
834 /*****************************************************************************/
835 /*
836  * link a key to a keyring
837  */
838 int key_link(struct key *keyring, struct key *key)
839 {
840         int ret;
841
842         key_check(keyring);
843         key_check(key);
844
845         down_write(&keyring->sem);
846         ret = __key_link(keyring, key);
847         up_write(&keyring->sem);
848
849         return ret;
850
851 } /* end key_link() */
852
853 EXPORT_SYMBOL(key_link);
854
855 /*****************************************************************************/
856 /*
857  * dispose of a keyring list after the RCU grace period, freeing the unlinked
858  * key
859  */
860 static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
861 {
862         struct keyring_list *klist =
863                 container_of(rcu, struct keyring_list, rcu);
864
865         key_put(klist->keys[klist->delkey]);
866         kfree(klist);
867
868 } /* end keyring_unlink_rcu_disposal() */
869
870 /*****************************************************************************/
871 /*
872  * unlink the first link to a key from a keyring
873  */
874 int key_unlink(struct key *keyring, struct key *key)
875 {
876         struct keyring_list *klist, *nklist;
877         int loop, ret;
878
879         key_check(keyring);
880         key_check(key);
881
882         ret = -ENOTDIR;
883         if (keyring->type != &key_type_keyring)
884                 goto error;
885
886         down_write(&keyring->sem);
887
888         klist = keyring->payload.subscriptions;
889         if (klist) {
890                 /* search the keyring for the key */
891                 for (loop = 0; loop < klist->nkeys; loop++)
892                         if (klist->keys[loop] == key)
893                                 goto key_is_present;
894         }
895
896         up_write(&keyring->sem);
897         ret = -ENOENT;
898         goto error;
899
900 key_is_present:
901         /* we need to copy the key list for RCU purposes */
902         nklist = kmalloc(sizeof(*klist) +
903                          sizeof(struct key *) * klist->maxkeys,
904                          GFP_KERNEL);
905         if (!nklist)
906                 goto nomem;
907         nklist->maxkeys = klist->maxkeys;
908         nklist->nkeys = klist->nkeys - 1;
909
910         if (loop > 0)
911                 memcpy(&nklist->keys[0],
912                        &klist->keys[0],
913                        loop * sizeof(struct key *));
914
915         if (loop < nklist->nkeys)
916                 memcpy(&nklist->keys[loop],
917                        &klist->keys[loop + 1],
918                        (nklist->nkeys - loop) * sizeof(struct key *));
919
920         /* adjust the user's quota */
921         key_payload_reserve(keyring,
922                             keyring->datalen - KEYQUOTA_LINK_BYTES);
923
924         rcu_assign_pointer(keyring->payload.subscriptions, nklist);
925
926         up_write(&keyring->sem);
927
928         /* schedule for later cleanup */
929         klist->delkey = loop;
930         call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
931
932         ret = 0;
933
934 error:
935         return ret;
936 nomem:
937         ret = -ENOMEM;
938         up_write(&keyring->sem);
939         goto error;
940
941 } /* end key_unlink() */
942
943 EXPORT_SYMBOL(key_unlink);
944
945 /*****************************************************************************/
946 /*
947  * dispose of a keyring list after the RCU grace period, releasing the keys it
948  * links to
949  */
950 static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
951 {
952         struct keyring_list *klist;
953         int loop;
954
955         klist = container_of(rcu, struct keyring_list, rcu);
956
957         for (loop = klist->nkeys - 1; loop >= 0; loop--)
958                 key_put(klist->keys[loop]);
959
960         kfree(klist);
961
962 } /* end keyring_clear_rcu_disposal() */
963
964 /*****************************************************************************/
965 /*
966  * clear the specified process keyring
967  * - implements keyctl(KEYCTL_CLEAR)
968  */
969 int keyring_clear(struct key *keyring)
970 {
971         struct keyring_list *klist;
972         int ret;
973
974         ret = -ENOTDIR;
975         if (keyring->type == &key_type_keyring) {
976                 /* detach the pointer block with the locks held */
977                 down_write(&keyring->sem);
978
979                 klist = keyring->payload.subscriptions;
980                 if (klist) {
981                         /* adjust the quota */
982                         key_payload_reserve(keyring,
983                                             sizeof(struct keyring_list));
984
985                         rcu_assign_pointer(keyring->payload.subscriptions,
986                                            NULL);
987                 }
988
989                 up_write(&keyring->sem);
990
991                 /* free the keys after the locks have been dropped */
992                 if (klist)
993                         call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
994
995                 ret = 0;
996         }
997
998         return ret;
999
1000 } /* end keyring_clear() */
1001
1002 EXPORT_SYMBOL(keyring_clear);