From cab8eb594e84b434d20412fc5a3985b0bee3ab9f Mon Sep 17 00:00:00 2001 From: David Howells Date: Sun, 8 Jan 2006 01:02:45 -0800 Subject: [PATCH] keys: Discard duplicate keys from a keyring on link Cause any links within a keyring to keys that match a key to be linked into that keyring to be discarded as a link to the new key is added. The match is contingent on the type and description strings being the same. This permits requests, adds and searches to displace negative, expired, revoked and dead keys easily. After some discussion it was concluded that duplicate valid keys should probably be discarded also as they would otherwise hide the new key. Since request_key() is intended to be the primary method by which keys are added to a keyring, duplicate valid keys wouldn't be an issue there as that function would return an existing match in preference to creating a new key. Signed-off-by: David Howells Cc: Trond Myklebust Cc: Alexander Zangerl Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- security/keys/keyring.c | 87 ++++++++++++++++++++++++++++++++++++------------- 1 file changed, 64 insertions(+), 23 deletions(-) (limited to 'security') diff --git a/security/keys/keyring.c b/security/keys/keyring.c index 5d22c0388b32..09d92d52ef75 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -682,17 +682,33 @@ static void keyring_link_rcu_disposal(struct rcu_head *rcu) } /* end keyring_link_rcu_disposal() */ +/*****************************************************************************/ +/* + * dispose of a keyring list after the RCU grace period, freeing the unlinked + * key + */ +static void keyring_unlink_rcu_disposal(struct rcu_head *rcu) +{ + struct keyring_list *klist = + container_of(rcu, struct keyring_list, rcu); + + key_put(klist->keys[klist->delkey]); + kfree(klist); + +} /* end keyring_unlink_rcu_disposal() */ + /*****************************************************************************/ /* * link a key into to a keyring * - must be called with the keyring's semaphore write-locked + * - discard already extant link to matching key if there is one */ int __key_link(struct key *keyring, struct key *key) { struct keyring_list *klist, *nklist; unsigned max; size_t size; - int ret; + int loop, ret; ret = -EKEYREVOKED; if (test_bit(KEY_FLAG_REVOKED, &keyring->flags)) @@ -714,6 +730,48 @@ int __key_link(struct key *keyring, struct key *key) goto error2; } + /* see if there's a matching key we can displace */ + klist = keyring->payload.subscriptions; + + if (klist && klist->nkeys > 0) { + struct key_type *type = key->type; + + for (loop = klist->nkeys - 1; loop >= 0; loop--) { + if (klist->keys[loop]->type == type && + strcmp(klist->keys[loop]->description, + key->description) == 0 + ) { + /* found a match - replace with new key */ + size = sizeof(struct key *) * klist->maxkeys; + size += sizeof(*klist); + BUG_ON(size > PAGE_SIZE); + + ret = -ENOMEM; + nklist = kmalloc(size, GFP_KERNEL); + if (!nklist) + goto error2; + + memcpy(nklist, klist, size); + + /* replace matched key */ + atomic_inc(&key->usage); + nklist->keys[loop] = key; + + rcu_assign_pointer( + keyring->payload.subscriptions, + nklist); + + /* dispose of the old keyring list and the + * displaced key */ + klist->delkey = loop; + call_rcu(&klist->rcu, + keyring_unlink_rcu_disposal); + + goto done; + } + } + } + /* check that we aren't going to overrun the user's quota */ ret = key_payload_reserve(keyring, keyring->datalen + KEYQUOTA_LINK_BYTES); @@ -730,8 +788,6 @@ int __key_link(struct key *keyring, struct key *key) smp_wmb(); klist->nkeys++; smp_wmb(); - - ret = 0; } else { /* grow the key list */ @@ -769,16 +825,16 @@ int __key_link(struct key *keyring, struct key *key) /* dispose of the old keyring list */ if (klist) call_rcu(&klist->rcu, keyring_link_rcu_disposal); - - ret = 0; } - error2: +done: + ret = 0; +error2: up_write(&keyring_serialise_link_sem); - error: +error: return ret; - error3: +error3: /* undo the quota changes */ key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES); @@ -807,21 +863,6 @@ int key_link(struct key *keyring, struct key *key) EXPORT_SYMBOL(key_link); -/*****************************************************************************/ -/* - * dispose of a keyring list after the RCU grace period, freeing the unlinked - * key - */ -static void keyring_unlink_rcu_disposal(struct rcu_head *rcu) -{ - struct keyring_list *klist = - container_of(rcu, struct keyring_list, rcu); - - key_put(klist->keys[klist->delkey]); - kfree(klist); - -} /* end keyring_unlink_rcu_disposal() */ - /*****************************************************************************/ /* * unlink the first link to a key from a keyring -- cgit v1.2.3