Linux-2.6.12-rc2
[linux-3.10.git] / security / keys / keyring.c
1 /* keyring.c: keyring handling
2  *
3  * Copyright (C) 2004 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         sklist = source->payload.subscriptions;
136
137         if (sklist && sklist->nkeys > 0) {
138                 max = sklist->nkeys;
139                 BUG_ON(max > limit);
140
141                 max = (max + 3) & ~3;
142                 if (max > limit)
143                         max = limit;
144
145                 ret = -ENOMEM;
146                 size = sizeof(*klist) + sizeof(struct key) * max;
147                 klist = kmalloc(size, GFP_KERNEL);
148                 if (!klist)
149                         goto error;
150
151                 klist->maxkeys = max;
152                 klist->nkeys = sklist->nkeys;
153                 memcpy(klist->keys,
154                        sklist->keys,
155                        sklist->nkeys * sizeof(struct key));
156
157                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
158                         atomic_inc(&klist->keys[loop]->usage);
159
160                 keyring->payload.subscriptions = klist;
161                 ret = 0;
162         }
163
164  error:
165         return ret;
166
167 } /* end keyring_duplicate() */
168
169 /*****************************************************************************/
170 /*
171  * match keyrings on their name
172  */
173 static int keyring_match(const struct key *keyring, const void *description)
174 {
175         return keyring->description &&
176                 strcmp(keyring->description, description) == 0;
177
178 } /* end keyring_match() */
179
180 /*****************************************************************************/
181 /*
182  * dispose of the data dangling from the corpse of a keyring
183  */
184 static void keyring_destroy(struct key *keyring)
185 {
186         struct keyring_list *klist;
187         int loop;
188
189         if (keyring->description) {
190                 write_lock(&keyring_name_lock);
191                 list_del(&keyring->type_data.link);
192                 write_unlock(&keyring_name_lock);
193         }
194
195         klist = keyring->payload.subscriptions;
196         if (klist) {
197                 for (loop = klist->nkeys - 1; loop >= 0; loop--)
198                         key_put(klist->keys[loop]);
199                 kfree(klist);
200         }
201
202 } /* end keyring_destroy() */
203
204 /*****************************************************************************/
205 /*
206  * describe the keyring
207  */
208 static void keyring_describe(const struct key *keyring, struct seq_file *m)
209 {
210         struct keyring_list *klist;
211
212         if (keyring->description) {
213                 seq_puts(m, keyring->description);
214         }
215         else {
216                 seq_puts(m, "[anon]");
217         }
218
219         klist = keyring->payload.subscriptions;
220         if (klist)
221                 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
222         else
223                 seq_puts(m, ": empty");
224
225 } /* end keyring_describe() */
226
227 /*****************************************************************************/
228 /*
229  * read a list of key IDs from the keyring's contents
230  */
231 static long keyring_read(const struct key *keyring,
232                          char __user *buffer, size_t buflen)
233 {
234         struct keyring_list *klist;
235         struct key *key;
236         size_t qty, tmp;
237         int loop, ret;
238
239         ret = 0;
240         klist = keyring->payload.subscriptions;
241
242         if (klist) {
243                 /* calculate how much data we could return */
244                 qty = klist->nkeys * sizeof(key_serial_t);
245
246                 if (buffer && buflen > 0) {
247                         if (buflen > qty)
248                                 buflen = qty;
249
250                         /* copy the IDs of the subscribed keys into the
251                          * buffer */
252                         ret = -EFAULT;
253
254                         for (loop = 0; loop < klist->nkeys; loop++) {
255                                 key = klist->keys[loop];
256
257                                 tmp = sizeof(key_serial_t);
258                                 if (tmp > buflen)
259                                         tmp = buflen;
260
261                                 if (copy_to_user(buffer,
262                                                  &key->serial,
263                                                  tmp) != 0)
264                                         goto error;
265
266                                 buflen -= tmp;
267                                 if (buflen == 0)
268                                         break;
269                                 buffer += tmp;
270                         }
271                 }
272
273                 ret = qty;
274         }
275
276  error:
277         return ret;
278
279 } /* end keyring_read() */
280
281 /*****************************************************************************/
282 /*
283  * allocate a keyring and link into the destination keyring
284  */
285 struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
286                           int not_in_quota, struct key *dest)
287 {
288         struct key *keyring;
289         int ret;
290
291         keyring = key_alloc(&key_type_keyring, description,
292                             uid, gid, KEY_USR_ALL, not_in_quota);
293
294         if (!IS_ERR(keyring)) {
295                 ret = key_instantiate_and_link(keyring, NULL, 0, dest);
296                 if (ret < 0) {
297                         key_put(keyring);
298                         keyring = ERR_PTR(ret);
299                 }
300         }
301
302         return keyring;
303
304 } /* end keyring_alloc() */
305
306 /*****************************************************************************/
307 /*
308  * search the supplied keyring tree for a key that matches the criterion
309  * - perform a breadth-then-depth search up to the prescribed limit
310  * - we only find keys on which we have search permission
311  * - we use the supplied match function to see if the description (or other
312  *   feature of interest) matches
313  * - we readlock the keyrings as we search down the tree
314  * - we return -EAGAIN if we didn't find any matching key
315  * - we return -ENOKEY if we only found negative matching keys
316  */
317 struct key *keyring_search_aux(struct key *keyring,
318                                struct key_type *type,
319                                const void *description,
320                                key_match_func_t match)
321 {
322         struct {
323                 struct key *keyring;
324                 int kix;
325         } stack[KEYRING_SEARCH_MAX_DEPTH];
326
327         struct keyring_list *keylist;
328         struct timespec now;
329         struct key *key;
330         long err;
331         int sp, psp, kix;
332
333         key_check(keyring);
334
335         /* top keyring must have search permission to begin the search */
336         key = ERR_PTR(-EACCES);
337         if (!key_permission(keyring, KEY_SEARCH))
338                 goto error;
339
340         key = ERR_PTR(-ENOTDIR);
341         if (keyring->type != &key_type_keyring)
342                 goto error;
343
344         now = current_kernel_time();
345         err = -EAGAIN;
346         sp = 0;
347
348         /* start processing a new keyring */
349  descend:
350         read_lock(&keyring->lock);
351         if (keyring->flags & KEY_FLAG_REVOKED)
352                 goto not_this_keyring;
353
354         keylist = keyring->payload.subscriptions;
355         if (!keylist)
356                 goto not_this_keyring;
357
358         /* iterate through the keys in this keyring first */
359         for (kix = 0; kix < keylist->nkeys; kix++) {
360                 key = keylist->keys[kix];
361
362                 /* ignore keys not of this type */
363                 if (key->type != type)
364                         continue;
365
366                 /* skip revoked keys and expired keys */
367                 if (key->flags & KEY_FLAG_REVOKED)
368                         continue;
369
370                 if (key->expiry && now.tv_sec >= key->expiry)
371                         continue;
372
373                 /* keys that don't match */
374                 if (!match(key, description))
375                         continue;
376
377                 /* key must have search permissions */
378                 if (!key_permission(key, KEY_SEARCH))
379                         continue;
380
381                 /* we set a different error code if we find a negative key */
382                 if (key->flags & KEY_FLAG_NEGATIVE) {
383                         err = -ENOKEY;
384                         continue;
385                 }
386
387                 goto found;
388         }
389
390         /* search through the keyrings nested in this one */
391         kix = 0;
392  ascend:
393         while (kix < keylist->nkeys) {
394                 key = keylist->keys[kix];
395                 if (key->type != &key_type_keyring)
396                         goto next;
397
398                 /* recursively search nested keyrings
399                  * - only search keyrings for which we have search permission
400                  */
401                 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
402                         goto next;
403
404                 if (!key_permission(key, KEY_SEARCH))
405                         goto next;
406
407                 /* evade loops in the keyring tree */
408                 for (psp = 0; psp < sp; psp++)
409                         if (stack[psp].keyring == keyring)
410                                 goto next;
411
412                 /* stack the current position */
413                 stack[sp].keyring = keyring;
414                 stack[sp].kix = kix;
415                 sp++;
416
417                 /* begin again with the new keyring */
418                 keyring = key;
419                 goto descend;
420
421         next:
422                 kix++;
423         }
424
425         /* the keyring we're looking at was disqualified or didn't contain a
426          * matching key */
427  not_this_keyring:
428         read_unlock(&keyring->lock);
429
430         if (sp > 0) {
431                 /* resume the processing of a keyring higher up in the tree */
432                 sp--;
433                 keyring = stack[sp].keyring;
434                 keylist = keyring->payload.subscriptions;
435                 kix = stack[sp].kix + 1;
436                 goto ascend;
437         }
438
439         key = ERR_PTR(err);
440         goto error;
441
442         /* we found a viable match */
443  found:
444         atomic_inc(&key->usage);
445         read_unlock(&keyring->lock);
446
447         /* unwind the keyring stack */
448         while (sp > 0) {
449                 sp--;
450                 read_unlock(&stack[sp].keyring->lock);
451         }
452
453         key_check(key);
454  error:
455         return key;
456
457 } /* end keyring_search_aux() */
458
459 /*****************************************************************************/
460 /*
461  * search the supplied keyring tree for a key that matches the criterion
462  * - perform a breadth-then-depth search up to the prescribed limit
463  * - we only find keys on which we have search permission
464  * - we readlock the keyrings as we search down the tree
465  * - we return -EAGAIN if we didn't find any matching key
466  * - we return -ENOKEY if we only found negative matching keys
467  */
468 struct key *keyring_search(struct key *keyring,
469                            struct key_type *type,
470                            const char *description)
471 {
472         return keyring_search_aux(keyring, type, description, type->match);
473
474 } /* end keyring_search() */
475
476 EXPORT_SYMBOL(keyring_search);
477
478 /*****************************************************************************/
479 /*
480  * search the given keyring only (no recursion)
481  * - keyring must be locked by caller
482  */
483 struct key *__keyring_search_one(struct key *keyring,
484                                  const struct key_type *ktype,
485                                  const char *description,
486                                  key_perm_t perm)
487 {
488         struct keyring_list *klist;
489         struct key *key;
490         int loop;
491
492         klist = keyring->payload.subscriptions;
493         if (klist) {
494                 for (loop = 0; loop < klist->nkeys; loop++) {
495                         key = klist->keys[loop];
496
497                         if (key->type == ktype &&
498                             key->type->match(key, description) &&
499                             key_permission(key, perm) &&
500                             !(key->flags & KEY_FLAG_REVOKED)
501                             )
502                                 goto found;
503                 }
504         }
505
506         key = ERR_PTR(-ENOKEY);
507         goto error;
508
509  found:
510         atomic_inc(&key->usage);
511  error:
512         return key;
513
514 } /* end __keyring_search_one() */
515
516 /*****************************************************************************/
517 /*
518  * find a keyring with the specified name
519  * - all named keyrings are searched
520  * - only find keyrings with search permission for the process
521  * - only find keyrings with a serial number greater than the one specified
522  */
523 struct key *find_keyring_by_name(const char *name, key_serial_t bound)
524 {
525         struct key *keyring;
526         int bucket;
527
528         keyring = ERR_PTR(-EINVAL);
529         if (!name)
530                 goto error;
531
532         bucket = keyring_hash(name);
533
534         read_lock(&keyring_name_lock);
535
536         if (keyring_name_hash[bucket].next) {
537                 /* search this hash bucket for a keyring with a matching name
538                  * that's readable and that hasn't been revoked */
539                 list_for_each_entry(keyring,
540                                     &keyring_name_hash[bucket],
541                                     type_data.link
542                                     ) {
543                         if (keyring->flags & KEY_FLAG_REVOKED)
544                                 continue;
545
546                         if (strcmp(keyring->description, name) != 0)
547                                 continue;
548
549                         if (!key_permission(keyring, KEY_SEARCH))
550                                 continue;
551
552                         /* found a potential candidate, but we still need to
553                          * check the serial number */
554                         if (keyring->serial <= bound)
555                                 continue;
556
557                         /* we've got a match */
558                         atomic_inc(&keyring->usage);
559                         read_unlock(&keyring_name_lock);
560                         goto error;
561                 }
562         }
563
564         read_unlock(&keyring_name_lock);
565         keyring = ERR_PTR(-ENOKEY);
566
567  error:
568         return keyring;
569
570 } /* end find_keyring_by_name() */
571
572 /*****************************************************************************/
573 /*
574  * see if a cycle will will be created by inserting acyclic tree B in acyclic
575  * tree A at the topmost level (ie: as a direct child of A)
576  * - since we are adding B to A at the top level, checking for cycles should
577  *   just be a matter of seeing if node A is somewhere in tree B
578  */
579 static int keyring_detect_cycle(struct key *A, struct key *B)
580 {
581         struct {
582                 struct key *subtree;
583                 int kix;
584         } stack[KEYRING_SEARCH_MAX_DEPTH];
585
586         struct keyring_list *keylist;
587         struct key *subtree, *key;
588         int sp, kix, ret;
589
590         ret = -EDEADLK;
591         if (A == B)
592                 goto error;
593
594         subtree = B;
595         sp = 0;
596
597         /* start processing a new keyring */
598  descend:
599         read_lock(&subtree->lock);
600         if (subtree->flags & KEY_FLAG_REVOKED)
601                 goto not_this_keyring;
602
603         keylist = subtree->payload.subscriptions;
604         if (!keylist)
605                 goto not_this_keyring;
606         kix = 0;
607
608  ascend:
609         /* iterate through the remaining keys in this keyring */
610         for (; kix < keylist->nkeys; kix++) {
611                 key = keylist->keys[kix];
612
613                 if (key == A)
614                         goto cycle_detected;
615
616                 /* recursively check nested keyrings */
617                 if (key->type == &key_type_keyring) {
618                         if (sp >= KEYRING_SEARCH_MAX_DEPTH)
619                                 goto too_deep;
620
621                         /* stack the current position */
622                         stack[sp].subtree = subtree;
623                         stack[sp].kix = kix;
624                         sp++;
625
626                         /* begin again with the new keyring */
627                         subtree = key;
628                         goto descend;
629                 }
630         }
631
632         /* the keyring we're looking at was disqualified or didn't contain a
633          * matching key */
634  not_this_keyring:
635         read_unlock(&subtree->lock);
636
637         if (sp > 0) {
638                 /* resume the checking of a keyring higher up in the tree */
639                 sp--;
640                 subtree = stack[sp].subtree;
641                 keylist = subtree->payload.subscriptions;
642                 kix = stack[sp].kix + 1;
643                 goto ascend;
644         }
645
646         ret = 0; /* no cycles detected */
647
648  error:
649         return ret;
650
651  too_deep:
652         ret = -ELOOP;
653         goto error_unwind;
654  cycle_detected:
655         ret = -EDEADLK;
656  error_unwind:
657         read_unlock(&subtree->lock);
658
659         /* unwind the keyring stack */
660         while (sp > 0) {
661                 sp--;
662                 read_unlock(&stack[sp].subtree->lock);
663         }
664
665         goto error;
666
667 } /* end keyring_detect_cycle() */
668
669 /*****************************************************************************/
670 /*
671  * link a key into to a keyring
672  * - must be called with the keyring's semaphore held
673  */
674 int __key_link(struct key *keyring, struct key *key)
675 {
676         struct keyring_list *klist, *nklist;
677         unsigned max;
678         size_t size;
679         int ret;
680
681         ret = -EKEYREVOKED;
682         if (keyring->flags & KEY_FLAG_REVOKED)
683                 goto error;
684
685         ret = -ENOTDIR;
686         if (keyring->type != &key_type_keyring)
687                 goto error;
688
689         /* serialise link/link calls to prevent parallel calls causing a
690          * cycle when applied to two keyring in opposite orders */
691         down_write(&keyring_serialise_link_sem);
692
693         /* check that we aren't going to create a cycle adding one keyring to
694          * another */
695         if (key->type == &key_type_keyring) {
696                 ret = keyring_detect_cycle(keyring, key);
697                 if (ret < 0)
698                         goto error2;
699         }
700
701         /* check that we aren't going to overrun the user's quota */
702         ret = key_payload_reserve(keyring,
703                                   keyring->datalen + KEYQUOTA_LINK_BYTES);
704         if (ret < 0)
705                 goto error2;
706
707         klist = keyring->payload.subscriptions;
708
709         if (klist && klist->nkeys < klist->maxkeys) {
710                 /* there's sufficient slack space to add directly */
711                 atomic_inc(&key->usage);
712
713                 write_lock(&keyring->lock);
714                 klist->keys[klist->nkeys++] = key;
715                 write_unlock(&keyring->lock);
716
717                 ret = 0;
718         }
719         else {
720                 /* grow the key list */
721                 max = 4;
722                 if (klist)
723                         max += klist->maxkeys;
724
725                 ret = -ENFILE;
726                 size = sizeof(*klist) + sizeof(*key) * max;
727                 if (size > PAGE_SIZE)
728                         goto error3;
729
730                 ret = -ENOMEM;
731                 nklist = kmalloc(size, GFP_KERNEL);
732                 if (!nklist)
733                         goto error3;
734                 nklist->maxkeys = max;
735                 nklist->nkeys = 0;
736
737                 if (klist) {
738                         nklist->nkeys = klist->nkeys;
739                         memcpy(nklist->keys,
740                                klist->keys,
741                                sizeof(struct key *) * klist->nkeys);
742                 }
743
744                 /* add the key into the new space */
745                 atomic_inc(&key->usage);
746
747                 write_lock(&keyring->lock);
748                 keyring->payload.subscriptions = nklist;
749                 nklist->keys[nklist->nkeys++] = key;
750                 write_unlock(&keyring->lock);
751
752                 /* dispose of the old keyring list */
753                 kfree(klist);
754
755                 ret = 0;
756         }
757
758  error2:
759         up_write(&keyring_serialise_link_sem);
760  error:
761         return ret;
762
763  error3:
764         /* undo the quota changes */
765         key_payload_reserve(keyring,
766                             keyring->datalen - KEYQUOTA_LINK_BYTES);
767         goto error2;
768
769 } /* end __key_link() */
770
771 /*****************************************************************************/
772 /*
773  * link a key to a keyring
774  */
775 int key_link(struct key *keyring, struct key *key)
776 {
777         int ret;
778
779         key_check(keyring);
780         key_check(key);
781
782         down_write(&keyring->sem);
783         ret = __key_link(keyring, key);
784         up_write(&keyring->sem);
785
786         return ret;
787
788 } /* end key_link() */
789
790 EXPORT_SYMBOL(key_link);
791
792 /*****************************************************************************/
793 /*
794  * unlink the first link to a key from a keyring
795  */
796 int key_unlink(struct key *keyring, struct key *key)
797 {
798         struct keyring_list *klist;
799         int loop, ret;
800
801         key_check(keyring);
802         key_check(key);
803
804         ret = -ENOTDIR;
805         if (keyring->type != &key_type_keyring)
806                 goto error;
807
808         down_write(&keyring->sem);
809
810         klist = keyring->payload.subscriptions;
811         if (klist) {
812                 /* search the keyring for the key */
813                 for (loop = 0; loop < klist->nkeys; loop++)
814                         if (klist->keys[loop] == key)
815                                 goto key_is_present;
816         }
817
818         up_write(&keyring->sem);
819         ret = -ENOENT;
820         goto error;
821
822  key_is_present:
823         /* adjust the user's quota */
824         key_payload_reserve(keyring,
825                             keyring->datalen - KEYQUOTA_LINK_BYTES);
826
827         /* shuffle down the key pointers
828          * - it might be worth shrinking the allocated memory, but that runs
829          *   the risk of ENOMEM as we would have to copy
830          */
831         write_lock(&keyring->lock);
832
833         klist->nkeys--;
834         if (loop < klist->nkeys)
835                 memcpy(&klist->keys[loop],
836                        &klist->keys[loop + 1],
837                        (klist->nkeys - loop) * sizeof(struct key *));
838
839         write_unlock(&keyring->lock);
840
841         up_write(&keyring->sem);
842         key_put(key);
843         ret = 0;
844
845  error:
846         return ret;
847
848 } /* end key_unlink() */
849
850 EXPORT_SYMBOL(key_unlink);
851
852 /*****************************************************************************/
853 /*
854  * clear the specified process keyring
855  * - implements keyctl(KEYCTL_CLEAR)
856  */
857 int keyring_clear(struct key *keyring)
858 {
859         struct keyring_list *klist;
860         int loop, ret;
861
862         ret = -ENOTDIR;
863         if (keyring->type == &key_type_keyring) {
864                 /* detach the pointer block with the locks held */
865                 down_write(&keyring->sem);
866
867                 klist = keyring->payload.subscriptions;
868                 if (klist) {
869                         /* adjust the quota */
870                         key_payload_reserve(keyring,
871                                             sizeof(struct keyring_list));
872
873                         write_lock(&keyring->lock);
874                         keyring->payload.subscriptions = NULL;
875                         write_unlock(&keyring->lock);
876                 }
877
878                 up_write(&keyring->sem);
879
880                 /* free the keys after the locks have been dropped */
881                 if (klist) {
882                         for (loop = klist->nkeys - 1; loop >= 0; loop--)
883                                 key_put(klist->keys[loop]);
884
885                         kfree(klist);
886                 }
887
888                 ret = 0;
889         }
890
891         return ret;
892
893 } /* end keyring_clear() */
894
895 EXPORT_SYMBOL(keyring_clear);