3 * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/slab.h>
16 #include <linux/security.h>
17 #include <linux/seq_file.h>
18 #include <linux/err.h>
19 #include <keys/keyring-type.h>
20 #include <linux/uaccess.h>
23 #define rcu_dereference_locked_keyring(keyring) \
24 (rcu_dereference_protected( \
25 (keyring)->payload.subscriptions, \
26 rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
28 #define rcu_deref_link_locked(klist, index, keyring) \
29 (rcu_dereference_protected( \
30 (klist)->keys[index], \
31 rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
33 #define MAX_KEYRING_LINKS \
34 min_t(size_t, USHRT_MAX - 1, \
35 ((PAGE_SIZE - sizeof(struct keyring_list)) / sizeof(struct key *)))
37 #define KEY_LINK_FIXQUOTA 1UL
40 * When plumbing the depths of the key tree, this sets a hard limit
41 * set on how deep we're willing to go.
43 #define KEYRING_SEARCH_MAX_DEPTH 6
46 * We keep all named keyrings in a hash to speed looking them up.
48 #define KEYRING_NAME_HASH_SIZE (1 << 5)
50 static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
51 static DEFINE_RWLOCK(keyring_name_lock);
53 static inline unsigned keyring_hash(const char *desc)
58 bucket += (unsigned char)*desc;
60 return bucket & (KEYRING_NAME_HASH_SIZE - 1);
64 * The keyring key type definition. Keyrings are simply keys of this type and
65 * can be treated as ordinary keys in addition to having their own special
68 static int keyring_instantiate(struct key *keyring,
69 const void *data, size_t datalen);
70 static int keyring_match(const struct key *keyring, const void *criterion);
71 static void keyring_revoke(struct key *keyring);
72 static void keyring_destroy(struct key *keyring);
73 static void keyring_describe(const struct key *keyring, struct seq_file *m);
74 static long keyring_read(const struct key *keyring,
75 char __user *buffer, size_t buflen);
77 struct key_type key_type_keyring = {
79 .def_datalen = sizeof(struct keyring_list),
80 .instantiate = keyring_instantiate,
81 .match = keyring_match,
82 .revoke = keyring_revoke,
83 .destroy = keyring_destroy,
84 .describe = keyring_describe,
87 EXPORT_SYMBOL(key_type_keyring);
90 * Semaphore to serialise link/link calls to prevent two link calls in parallel
91 * introducing a cycle.
93 static DECLARE_RWSEM(keyring_serialise_link_sem);
96 * Publish the name of a keyring so that it can be found by name (if it has
99 static void keyring_publish_name(struct key *keyring)
103 if (keyring->description) {
104 bucket = keyring_hash(keyring->description);
106 write_lock(&keyring_name_lock);
108 if (!keyring_name_hash[bucket].next)
109 INIT_LIST_HEAD(&keyring_name_hash[bucket]);
111 list_add_tail(&keyring->type_data.link,
112 &keyring_name_hash[bucket]);
114 write_unlock(&keyring_name_lock);
119 * Initialise a keyring.
121 * Returns 0 on success, -EINVAL if given any data.
123 static int keyring_instantiate(struct key *keyring,
124 const void *data, size_t datalen)
130 /* make the keyring available by name if it has one */
131 keyring_publish_name(keyring);
139 * Match keyrings on their name
141 static int keyring_match(const struct key *keyring, const void *description)
143 return keyring->description &&
144 strcmp(keyring->description, description) == 0;
148 * Clean up a keyring when it is destroyed. Unpublish its name if it had one
149 * and dispose of its data.
151 * The garbage collector detects the final key_put(), removes the keyring from
152 * the serial number tree and then does RCU synchronisation before coming here,
153 * so we shouldn't need to worry about code poking around here with the RCU
154 * readlock held by this time.
156 static void keyring_destroy(struct key *keyring)
158 struct keyring_list *klist;
161 if (keyring->description) {
162 write_lock(&keyring_name_lock);
164 if (keyring->type_data.link.next != NULL &&
165 !list_empty(&keyring->type_data.link))
166 list_del(&keyring->type_data.link);
168 write_unlock(&keyring_name_lock);
171 klist = rcu_access_pointer(keyring->payload.subscriptions);
173 for (loop = klist->nkeys - 1; loop >= 0; loop--)
174 key_put(rcu_access_pointer(klist->keys[loop]));
180 * Describe a keyring for /proc.
182 static void keyring_describe(const struct key *keyring, struct seq_file *m)
184 struct keyring_list *klist;
186 if (keyring->description)
187 seq_puts(m, keyring->description);
189 seq_puts(m, "[anon]");
191 if (key_is_instantiated(keyring)) {
193 klist = rcu_dereference(keyring->payload.subscriptions);
195 seq_printf(m, ": %u/%u", klist->nkeys, klist->maxkeys);
197 seq_puts(m, ": empty");
203 * Read a list of key IDs from the keyring's contents in binary form
205 * The keyring's semaphore is read-locked by the caller.
207 static long keyring_read(const struct key *keyring,
208 char __user *buffer, size_t buflen)
210 struct keyring_list *klist;
216 klist = rcu_dereference_locked_keyring(keyring);
218 /* calculate how much data we could return */
219 qty = klist->nkeys * sizeof(key_serial_t);
221 if (buffer && buflen > 0) {
225 /* copy the IDs of the subscribed keys into the
229 for (loop = 0; loop < klist->nkeys; loop++) {
230 key = rcu_deref_link_locked(klist, loop,
233 tmp = sizeof(key_serial_t);
237 if (copy_to_user(buffer,
257 * Allocate a keyring and link into the destination keyring.
259 struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
260 const struct cred *cred, unsigned long flags,
266 keyring = key_alloc(&key_type_keyring, description,
268 (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
271 if (!IS_ERR(keyring)) {
272 ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
275 keyring = ERR_PTR(ret);
283 * keyring_search_aux - Search a keyring tree for a key matching some criteria
284 * @keyring_ref: A pointer to the keyring with possession indicator.
285 * @cred: The credentials to use for permissions checks.
286 * @type: The type of key to search for.
287 * @description: Parameter for @match.
288 * @match: Function to rule on whether or not a key is the one required.
289 * @no_state_check: Don't check if a matching key is bad
291 * Search the supplied keyring tree for a key that matches the criteria given.
292 * The root keyring and any linked keyrings must grant Search permission to the
293 * caller to be searchable and keys can only be found if they too grant Search
294 * to the caller. The possession flag on the root keyring pointer controls use
295 * of the possessor bits in permissions checking of the entire tree. In
296 * addition, the LSM gets to forbid keyring searches and key matches.
298 * The search is performed as a breadth-then-depth search up to the prescribed
299 * limit (KEYRING_SEARCH_MAX_DEPTH).
301 * Keys are matched to the type provided and are then filtered by the match
302 * function, which is given the description to use in any way it sees fit. The
303 * match function may use any attributes of a key that it wishes to to
304 * determine the match. Normally the match function from the key type would be
307 * RCU is used to prevent the keyring key lists from disappearing without the
308 * need to take lots of locks.
310 * Returns a pointer to the found key and increments the key usage count if
311 * successful; -EAGAIN if no matching keys were found, or if expired or revoked
312 * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
313 * specified keyring wasn't a keyring.
315 * In the case of a successful return, the possession attribute from
316 * @keyring_ref is propagated to the returned key reference.
318 key_ref_t keyring_search_aux(key_ref_t keyring_ref,
319 const struct cred *cred,
320 struct key_type *type,
321 const void *description,
322 key_match_func_t match,
326 /* Need a separate keylist pointer for RCU purposes */
328 struct keyring_list *keylist;
330 } stack[KEYRING_SEARCH_MAX_DEPTH];
332 struct keyring_list *keylist;
334 unsigned long possessed, kflags;
335 struct key *keyring, *key;
340 keyring = key_ref_to_ptr(keyring_ref);
341 possessed = is_key_possessed(keyring_ref);
344 /* top keyring must have search permission to begin the search */
345 err = key_task_permission(keyring_ref, cred, KEY_SEARCH);
347 key_ref = ERR_PTR(err);
351 key_ref = ERR_PTR(-ENOTDIR);
352 if (keyring->type != &key_type_keyring)
357 now = current_kernel_time();
361 /* firstly we should check to see if this top-level keyring is what we
363 key_ref = ERR_PTR(-EAGAIN);
364 kflags = keyring->flags;
365 if (keyring->type == type && match(keyring, description)) {
370 /* check it isn't negative and hasn't expired or been
372 if (kflags & (1 << KEY_FLAG_REVOKED))
374 if (key->expiry && now.tv_sec >= key->expiry)
376 key_ref = ERR_PTR(key->type_data.reject_error);
377 if (kflags & (1 << KEY_FLAG_NEGATIVE))
382 /* otherwise, the top keyring must not be revoked, expired, or
383 * negatively instantiated if we are to search it */
384 key_ref = ERR_PTR(-EAGAIN);
385 if (kflags & ((1 << KEY_FLAG_REVOKED) | (1 << KEY_FLAG_NEGATIVE)) ||
386 (keyring->expiry && now.tv_sec >= keyring->expiry))
389 /* start processing a new keyring */
391 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
392 goto not_this_keyring;
394 keylist = rcu_dereference(keyring->payload.subscriptions);
396 goto not_this_keyring;
398 /* iterate through the keys in this keyring first */
399 nkeys = keylist->nkeys;
401 for (kix = 0; kix < nkeys; kix++) {
402 key = rcu_dereference(keylist->keys[kix]);
405 /* ignore keys not of this type */
406 if (key->type != type)
409 /* skip revoked keys and expired keys */
410 if (!no_state_check) {
411 if (kflags & (1 << KEY_FLAG_REVOKED))
414 if (key->expiry && now.tv_sec >= key->expiry)
418 /* keys that don't match */
419 if (!match(key, description))
422 /* key must have search permissions */
423 if (key_task_permission(make_key_ref(key, possessed),
424 cred, KEY_SEARCH) < 0)
430 /* we set a different error code if we pass a negative key */
431 if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
432 err = key->type_data.reject_error;
439 /* search through the keyrings nested in this one */
442 nkeys = keylist->nkeys;
444 for (; kix < nkeys; kix++) {
445 key = rcu_dereference(keylist->keys[kix]);
446 if (key->type != &key_type_keyring)
449 /* recursively search nested keyrings
450 * - only search keyrings for which we have search permission
452 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
455 if (key_task_permission(make_key_ref(key, possessed),
456 cred, KEY_SEARCH) < 0)
459 /* stack the current position */
460 stack[sp].keyring = keyring;
461 stack[sp].keylist = keylist;
465 /* begin again with the new keyring */
470 /* the keyring we're looking at was disqualified or didn't contain a
474 /* resume the processing of a keyring higher up in the tree */
476 keyring = stack[sp].keyring;
477 keylist = stack[sp].keylist;
478 kix = stack[sp].kix + 1;
482 key_ref = ERR_PTR(err);
485 /* we found a viable match */
487 atomic_inc(&key->usage);
488 key->last_used_at = now.tv_sec;
489 keyring->last_used_at = now.tv_sec;
491 stack[--sp].keyring->last_used_at = now.tv_sec;
493 key_ref = make_key_ref(key, possessed);
501 * keyring_search - Search the supplied keyring tree for a matching key
502 * @keyring: The root of the keyring tree to be searched.
503 * @type: The type of keyring we want to find.
504 * @description: The name of the keyring we want to find.
506 * As keyring_search_aux() above, but using the current task's credentials and
507 * type's default matching function.
509 key_ref_t keyring_search(key_ref_t keyring,
510 struct key_type *type,
511 const char *description)
514 return ERR_PTR(-ENOKEY);
516 return keyring_search_aux(keyring, current->cred,
517 type, description, type->match, false);
519 EXPORT_SYMBOL(keyring_search);
522 * Search the given keyring only (no recursion).
524 * The caller must guarantee that the keyring is a keyring and that the
525 * permission is granted to search the keyring as no check is made here.
527 * RCU is used to make it unnecessary to lock the keyring key list here.
529 * Returns a pointer to the found key with usage count incremented if
530 * successful and returns -ENOKEY if not found. Revoked keys and keys not
531 * providing the requested permission are skipped over.
533 * If successful, the possession indicator is propagated from the keyring ref
534 * to the returned key reference.
536 key_ref_t __keyring_search_one(key_ref_t keyring_ref,
537 const struct key_type *ktype,
538 const char *description,
541 struct keyring_list *klist;
542 unsigned long possessed;
543 struct key *keyring, *key;
546 keyring = key_ref_to_ptr(keyring_ref);
547 possessed = is_key_possessed(keyring_ref);
551 klist = rcu_dereference(keyring->payload.subscriptions);
553 nkeys = klist->nkeys;
555 for (loop = 0; loop < nkeys ; loop++) {
556 key = rcu_dereference(klist->keys[loop]);
557 if (key->type == ktype &&
558 (!key->type->match ||
559 key->type->match(key, description)) &&
560 key_permission(make_key_ref(key, possessed),
562 !test_bit(KEY_FLAG_REVOKED, &key->flags)
569 return ERR_PTR(-ENOKEY);
572 atomic_inc(&key->usage);
573 keyring->last_used_at = key->last_used_at =
574 current_kernel_time().tv_sec;
576 return make_key_ref(key, possessed);
580 * Find a keyring with the specified name.
582 * All named keyrings in the current user namespace are searched, provided they
583 * grant Search permission directly to the caller (unless this check is
584 * skipped). Keyrings whose usage points have reached zero or who have been
585 * revoked are skipped.
587 * Returns a pointer to the keyring with the keyring's refcount having being
588 * incremented on success. -ENOKEY is returned if a key could not be found.
590 struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
596 return ERR_PTR(-EINVAL);
598 bucket = keyring_hash(name);
600 read_lock(&keyring_name_lock);
602 if (keyring_name_hash[bucket].next) {
603 /* search this hash bucket for a keyring with a matching name
604 * that's readable and that hasn't been revoked */
605 list_for_each_entry(keyring,
606 &keyring_name_hash[bucket],
609 if (keyring->user->user_ns != current_user_ns())
612 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
615 if (strcmp(keyring->description, name) != 0)
618 if (!skip_perm_check &&
619 key_permission(make_key_ref(keyring, 0),
623 /* we've got a match but we might end up racing with
624 * key_cleanup() if the keyring is currently 'dead'
625 * (ie. it has a zero usage count) */
626 if (!atomic_inc_not_zero(&keyring->usage))
628 keyring->last_used_at = current_kernel_time().tv_sec;
633 keyring = ERR_PTR(-ENOKEY);
635 read_unlock(&keyring_name_lock);
640 * See if a cycle will will be created by inserting acyclic tree B in acyclic
641 * tree A at the topmost level (ie: as a direct child of A).
643 * Since we are adding B to A at the top level, checking for cycles should just
644 * be a matter of seeing if node A is somewhere in tree B.
646 static int keyring_detect_cycle(struct key *A, struct key *B)
649 struct keyring_list *keylist;
651 } stack[KEYRING_SEARCH_MAX_DEPTH];
653 struct keyring_list *keylist;
654 struct key *subtree, *key;
655 int sp, nkeys, kix, ret;
666 /* start processing a new keyring */
668 if (test_bit(KEY_FLAG_REVOKED, &subtree->flags))
669 goto not_this_keyring;
671 keylist = rcu_dereference(subtree->payload.subscriptions);
673 goto not_this_keyring;
677 /* iterate through the remaining keys in this keyring */
678 nkeys = keylist->nkeys;
680 for (; kix < nkeys; kix++) {
681 key = rcu_dereference(keylist->keys[kix]);
686 /* recursively check nested keyrings */
687 if (key->type == &key_type_keyring) {
688 if (sp >= KEYRING_SEARCH_MAX_DEPTH)
691 /* stack the current position */
692 stack[sp].keylist = keylist;
696 /* begin again with the new keyring */
702 /* the keyring we're looking at was disqualified or didn't contain a
706 /* resume the checking of a keyring higher up in the tree */
708 keylist = stack[sp].keylist;
709 kix = stack[sp].kix + 1;
713 ret = 0; /* no cycles detected */
729 * Dispose of a keyring list after the RCU grace period, freeing the unlinked
732 static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
734 struct keyring_list *klist =
735 container_of(rcu, struct keyring_list, rcu);
737 if (klist->delkey != USHRT_MAX)
738 key_put(rcu_access_pointer(klist->keys[klist->delkey]));
743 * Preallocate memory so that a key can be linked into to a keyring.
745 int __key_link_begin(struct key *keyring, const struct key_type *type,
746 const char *description, unsigned long *_prealloc)
747 __acquires(&keyring->sem)
749 struct keyring_list *klist, *nklist;
750 unsigned long prealloc;
756 kenter("%d,%s,%s,", key_serial(keyring), type->name, description);
758 if (keyring->type != &key_type_keyring)
761 down_write(&keyring->sem);
764 if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
767 /* serialise link/link calls to prevent parallel calls causing a cycle
768 * when linking two keyring in opposite orders */
769 if (type == &key_type_keyring)
770 down_write(&keyring_serialise_link_sem);
772 klist = rcu_dereference_locked_keyring(keyring);
774 /* see if there's a matching key we can displace */
776 if (klist && klist->nkeys > 0) {
777 lowest_lru = TIME_T_MAX;
778 for (loop = klist->nkeys - 1; loop >= 0; loop--) {
779 struct key *key = rcu_deref_link_locked(klist, loop,
781 if (key->type == type &&
782 strcmp(key->description, description) == 0) {
783 /* Found a match - we'll replace the link with
784 * one to the new key. We record the slot
787 klist->delkey = loop;
791 if (key->last_used_at < lowest_lru) {
792 lowest_lru = key->last_used_at;
798 /* If the keyring is full then do an LRU discard */
800 klist->nkeys == klist->maxkeys &&
801 klist->maxkeys >= MAX_KEYRING_LINKS) {
802 kdebug("LRU discard %d\n", lru);
808 /* check that we aren't going to overrun the user's quota */
809 ret = key_payload_reserve(keyring,
810 keyring->datalen + KEYQUOTA_LINK_BYTES);
814 if (klist && klist->nkeys < klist->maxkeys) {
815 /* there's sufficient slack space to append directly */
816 klist->delkey = klist->nkeys;
817 prealloc = KEY_LINK_FIXQUOTA;
819 /* grow the key list */
822 max += klist->maxkeys;
823 if (max > MAX_KEYRING_LINKS)
824 max = MAX_KEYRING_LINKS;
825 BUG_ON(max <= klist->maxkeys);
828 size = sizeof(*klist) + sizeof(struct key *) * max;
831 nklist = kmalloc(size, GFP_KERNEL);
835 nklist->maxkeys = max;
837 memcpy(nklist->keys, klist->keys,
838 sizeof(struct key *) * klist->nkeys);
839 nklist->delkey = klist->nkeys;
840 nklist->nkeys = klist->nkeys + 1;
841 klist->delkey = USHRT_MAX;
847 /* add the key into the new space */
848 RCU_INIT_POINTER(nklist->keys[nklist->delkey], NULL);
849 prealloc = (unsigned long)nklist | KEY_LINK_FIXQUOTA;
853 *_prealloc = prealloc;
858 /* undo the quota changes */
859 key_payload_reserve(keyring,
860 keyring->datalen - KEYQUOTA_LINK_BYTES);
862 if (type == &key_type_keyring)
863 up_write(&keyring_serialise_link_sem);
865 up_write(&keyring->sem);
866 kleave(" = %d", ret);
871 * Check already instantiated keys aren't going to be a problem.
873 * The caller must have called __key_link_begin(). Don't need to call this for
874 * keys that were created since __key_link_begin() was called.
876 int __key_link_check_live_key(struct key *keyring, struct key *key)
878 if (key->type == &key_type_keyring)
879 /* check that we aren't going to create a cycle by linking one
880 * keyring to another */
881 return keyring_detect_cycle(keyring, key);
886 * Link a key into to a keyring.
888 * Must be called with __key_link_begin() having being called. Discards any
889 * already extant link to matching key if there is one, so that each keyring
890 * holds at most one link to any given key of a particular type+description
893 void __key_link(struct key *keyring, struct key *key,
894 unsigned long *_prealloc)
896 struct keyring_list *klist, *nklist;
899 nklist = (struct keyring_list *)(*_prealloc & ~KEY_LINK_FIXQUOTA);
902 kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
904 klist = rcu_dereference_locked_keyring(keyring);
906 atomic_inc(&key->usage);
907 keyring->last_used_at = key->last_used_at =
908 current_kernel_time().tv_sec;
910 /* there's a matching key we can displace or an empty slot in a newly
911 * allocated list we can fill */
913 kdebug("reissue %hu/%hu/%hu",
914 nklist->delkey, nklist->nkeys, nklist->maxkeys);
916 RCU_INIT_POINTER(nklist->keys[nklist->delkey], key);
918 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
920 /* dispose of the old keyring list and, if there was one, the
923 kdebug("dispose %hu/%hu/%hu",
924 klist->delkey, klist->nkeys, klist->maxkeys);
925 call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
927 } else if (klist->delkey < klist->nkeys) {
928 kdebug("replace %hu/%hu/%hu",
929 klist->delkey, klist->nkeys, klist->maxkeys);
931 discard = rcu_dereference_protected(
932 klist->keys[klist->delkey],
933 rwsem_is_locked(&keyring->sem));
934 rcu_assign_pointer(klist->keys[klist->delkey], key);
935 /* The garbage collector will take care of RCU
939 /* there's sufficient slack space to append directly */
940 kdebug("append %hu/%hu/%hu",
941 klist->delkey, klist->nkeys, klist->maxkeys);
943 RCU_INIT_POINTER(klist->keys[klist->delkey], key);
950 * Finish linking a key into to a keyring.
952 * Must be called with __key_link_begin() having being called.
954 void __key_link_end(struct key *keyring, struct key_type *type,
955 unsigned long prealloc)
956 __releases(&keyring->sem)
958 BUG_ON(type == NULL);
959 BUG_ON(type->name == NULL);
960 kenter("%d,%s,%lx", keyring->serial, type->name, prealloc);
962 if (type == &key_type_keyring)
963 up_write(&keyring_serialise_link_sem);
966 if (prealloc & KEY_LINK_FIXQUOTA)
967 key_payload_reserve(keyring,
969 KEYQUOTA_LINK_BYTES);
970 kfree((struct keyring_list *)(prealloc & ~KEY_LINK_FIXQUOTA));
972 up_write(&keyring->sem);
976 * key_link - Link a key to a keyring
977 * @keyring: The keyring to make the link in.
978 * @key: The key to link to.
980 * Make a link in a keyring to a key, such that the keyring holds a reference
981 * on that key and the key can potentially be found by searching that keyring.
983 * This function will write-lock the keyring's semaphore and will consume some
984 * of the user's key data quota to hold the link.
986 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
987 * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
988 * full, -EDQUOT if there is insufficient key data quota remaining to add
989 * another link or -ENOMEM if there's insufficient memory.
991 * It is assumed that the caller has checked that it is permitted for a link to
992 * be made (the keyring should have Write permission and the key Link
995 int key_link(struct key *keyring, struct key *key)
997 unsigned long prealloc;
1003 ret = __key_link_begin(keyring, key->type, key->description, &prealloc);
1005 ret = __key_link_check_live_key(keyring, key);
1007 __key_link(keyring, key, &prealloc);
1008 __key_link_end(keyring, key->type, prealloc);
1013 EXPORT_SYMBOL(key_link);
1016 * key_unlink - Unlink the first link to a key from a keyring.
1017 * @keyring: The keyring to remove the link from.
1018 * @key: The key the link is to.
1020 * Remove a link from a keyring to a key.
1022 * This function will write-lock the keyring's semaphore.
1024 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
1025 * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
1028 * It is assumed that the caller has checked that it is permitted for a link to
1029 * be removed (the keyring should have Write permission; no permissions are
1030 * required on the key).
1032 int key_unlink(struct key *keyring, struct key *key)
1034 struct keyring_list *klist, *nklist;
1041 if (keyring->type != &key_type_keyring)
1044 down_write(&keyring->sem);
1046 klist = rcu_dereference_locked_keyring(keyring);
1048 /* search the keyring for the key */
1049 for (loop = 0; loop < klist->nkeys; loop++)
1050 if (rcu_access_pointer(klist->keys[loop]) == key)
1051 goto key_is_present;
1054 up_write(&keyring->sem);
1059 /* we need to copy the key list for RCU purposes */
1060 nklist = kmalloc(sizeof(*klist) +
1061 sizeof(struct key *) * klist->maxkeys,
1065 nklist->maxkeys = klist->maxkeys;
1066 nklist->nkeys = klist->nkeys - 1;
1069 memcpy(&nklist->keys[0],
1071 loop * sizeof(struct key *));
1073 if (loop < nklist->nkeys)
1074 memcpy(&nklist->keys[loop],
1075 &klist->keys[loop + 1],
1076 (nklist->nkeys - loop) * sizeof(struct key *));
1078 /* adjust the user's quota */
1079 key_payload_reserve(keyring,
1080 keyring->datalen - KEYQUOTA_LINK_BYTES);
1082 rcu_assign_pointer(keyring->payload.subscriptions, nklist);
1084 up_write(&keyring->sem);
1086 /* schedule for later cleanup */
1087 klist->delkey = loop;
1088 call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
1096 up_write(&keyring->sem);
1099 EXPORT_SYMBOL(key_unlink);
1102 * Dispose of a keyring list after the RCU grace period, releasing the keys it
1105 static void keyring_clear_rcu_disposal(struct rcu_head *rcu)
1107 struct keyring_list *klist;
1110 klist = container_of(rcu, struct keyring_list, rcu);
1112 for (loop = klist->nkeys - 1; loop >= 0; loop--)
1113 key_put(rcu_access_pointer(klist->keys[loop]));
1119 * keyring_clear - Clear a keyring
1120 * @keyring: The keyring to clear.
1122 * Clear the contents of the specified keyring.
1124 * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
1126 int keyring_clear(struct key *keyring)
1128 struct keyring_list *klist;
1132 if (keyring->type == &key_type_keyring) {
1133 /* detach the pointer block with the locks held */
1134 down_write(&keyring->sem);
1136 klist = rcu_dereference_locked_keyring(keyring);
1138 /* adjust the quota */
1139 key_payload_reserve(keyring,
1140 sizeof(struct keyring_list));
1142 rcu_assign_pointer(keyring->payload.subscriptions,
1146 up_write(&keyring->sem);
1148 /* free the keys after the locks have been dropped */
1150 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1157 EXPORT_SYMBOL(keyring_clear);
1160 * Dispose of the links from a revoked keyring.
1162 * This is called with the key sem write-locked.
1164 static void keyring_revoke(struct key *keyring)
1166 struct keyring_list *klist;
1168 klist = rcu_dereference_locked_keyring(keyring);
1170 /* adjust the quota */
1171 key_payload_reserve(keyring, 0);
1174 rcu_assign_pointer(keyring->payload.subscriptions, NULL);
1175 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1180 * Determine whether a key is dead.
1182 static bool key_is_dead(struct key *key, time_t limit)
1184 return test_bit(KEY_FLAG_DEAD, &key->flags) ||
1185 (key->expiry > 0 && key->expiry <= limit);
1189 * Collect garbage from the contents of a keyring, replacing the old list with
1190 * a new one with the pointers all shuffled down.
1192 * Dead keys are classed as oned that are flagged as being dead or are revoked,
1193 * expired or negative keys that were revoked or expired before the specified
1196 void keyring_gc(struct key *keyring, time_t limit)
1198 struct keyring_list *klist, *new;
1200 int loop, keep, max;
1202 kenter("{%x,%s}", key_serial(keyring), keyring->description);
1204 down_write(&keyring->sem);
1206 klist = rcu_dereference_locked_keyring(keyring);
1210 /* work out how many subscriptions we're keeping */
1212 for (loop = klist->nkeys - 1; loop >= 0; loop--)
1213 if (!key_is_dead(rcu_deref_link_locked(klist, loop, keyring),
1217 if (keep == klist->nkeys)
1220 /* allocate a new keyring payload */
1221 max = roundup(keep, 4);
1222 new = kmalloc(sizeof(struct keyring_list) + max * sizeof(struct key *),
1230 /* install the live keys
1231 * - must take care as expired keys may be updated back to life
1234 for (loop = klist->nkeys - 1; loop >= 0; loop--) {
1235 key = rcu_deref_link_locked(klist, loop, keyring);
1236 if (!key_is_dead(key, limit)) {
1239 RCU_INIT_POINTER(new->keys[keep++], key_get(key));
1244 /* adjust the quota */
1245 key_payload_reserve(keyring,
1246 sizeof(struct keyring_list) +
1247 KEYQUOTA_LINK_BYTES * keep);
1250 rcu_assign_pointer(keyring->payload.subscriptions, NULL);
1253 rcu_assign_pointer(keyring->payload.subscriptions, new);
1256 up_write(&keyring->sem);
1258 call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
1264 keyring_clear_rcu_disposal(&new->rcu);
1265 up_write(&keyring->sem);
1266 kleave(" [discard]");
1270 up_write(&keyring->sem);
1271 kleave(" [no dead]");
1275 up_write(&keyring->sem);
1276 kleave(" [no_klist]");
1280 up_write(&keyring->sem);