diff options
| -rw-r--r-- | Documentation/keys.txt | 4 | ||||
| -rw-r--r-- | security/keys/keyring.c | 87 |
2 files changed, 68 insertions, 23 deletions
diff --git a/Documentation/keys.txt b/Documentation/keys.txt index c17c4ca7430..eeda00f82d2 100644 --- a/Documentation/keys.txt +++ b/Documentation/keys.txt @@ -500,6 +500,10 @@ The keyctl syscall functions are: The link procedure checks the nesting of the keyrings, returning ELOOP if it appears too deep or EDEADLK if the link would introduce a cycle. + Any links within the keyring to keys that match the new key in terms of + type and description will be discarded from the keyring as the new one is + added. + (*) Unlink a key or keyring from another keyring: diff --git a/security/keys/keyring.c b/security/keys/keyring.c index 5d22c0388b3..09d92d52ef7 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -684,15 +684,31 @@ static void keyring_link_rcu_disposal(struct rcu_head *rcu) /*****************************************************************************/ /* + * 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); @@ -809,21 +865,6 @@ 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 */ int key_unlink(struct key *keyring, struct key *key) |