[PATCH] keys: Discard duplicate keys from a keyring on link

[pandora-kernel.git] / security / keys / keyring.c

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 5d22c03..09d92d5 100644 (file)
--- 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