Merge branch 'master' into next
[linux-3.10.git] / security / keys / keyring.c
index 29de5ee..3f425a6 100644 (file)
 #include <linux/uaccess.h>
 #include "internal.h"
 
+#define rcu_dereference_locked_keyring(keyring)                                \
+       (rcu_dereference_protected(                                     \
+               (keyring)->payload.subscriptions,                       \
+               rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
+
 /*
  * when plumbing the depths of the key tree, this sets a hard limit set on how
  * deep we're willing to go
@@ -199,8 +204,7 @@ static long keyring_read(const struct key *keyring,
        int loop, ret;
 
        ret = 0;
-       klist = keyring->payload.subscriptions;
-
+       klist = rcu_dereference_locked_keyring(keyring);
        if (klist) {
                /* calculate how much data we could return */
                qty = klist->nkeys * sizeof(key_serial_t);
@@ -524,9 +528,8 @@ struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
        struct key *keyring;
        int bucket;
 
-       keyring = ERR_PTR(-EINVAL);
        if (!name)
-               goto error;
+               return ERR_PTR(-EINVAL);
 
        bucket = keyring_hash(name);
 
@@ -553,17 +556,18 @@ struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
                                           KEY_SEARCH) < 0)
                                continue;
 
-                       /* we've got a match */
-                       atomic_inc(&keyring->usage);
-                       read_unlock(&keyring_name_lock);
-                       goto error;
+                       /* we've got a match but we might end up racing with
+                        * key_cleanup() if the keyring is currently 'dead'
+                        * (ie. it has a zero usage count) */
+                       if (!atomic_inc_not_zero(&keyring->usage))
+                               continue;
+                       goto out;
                }
        }
 
-       read_unlock(&keyring_name_lock);
        keyring = ERR_PTR(-ENOKEY);
-
-error:
+out:
+       read_unlock(&keyring_name_lock);
        return keyring;
 
 } /* end find_keyring_by_name() */
@@ -719,8 +723,7 @@ int __key_link(struct key *keyring, struct key *key)
        }
 
        /* see if there's a matching key we can displace */
-       klist = keyring->payload.subscriptions;
-
+       klist = rcu_dereference_locked_keyring(keyring);
        if (klist && klist->nkeys > 0) {
                struct key_type *type = key->type;
 
@@ -764,8 +767,6 @@ int __key_link(struct key *keyring, struct key *key)
        if (ret < 0)
                goto error2;
 
-       klist = keyring->payload.subscriptions;
-
        if (klist && klist->nkeys < klist->maxkeys) {
                /* there's sufficient slack space to add directly */
                atomic_inc(&key->usage);
@@ -867,7 +868,7 @@ int key_unlink(struct key *keyring, struct key *key)
 
        down_write(&keyring->sem);
 
-       klist = keyring->payload.subscriptions;
+       klist = rcu_dereference_locked_keyring(keyring);
        if (klist) {
                /* search the keyring for the key */
                for (loop = 0; loop < klist->nkeys; loop++)
@@ -958,7 +959,7 @@ int keyring_clear(struct key *keyring)
                /* detach the pointer block with the locks held */
                down_write(&keyring->sem);
 
-               klist = keyring->payload.subscriptions;
+               klist = rcu_dereference_locked_keyring(keyring);
                if (klist) {
                        /* adjust the quota */
                        key_payload_reserve(keyring,
@@ -990,7 +991,9 @@ EXPORT_SYMBOL(keyring_clear);
  */
 static void keyring_revoke(struct key *keyring)
 {
-       struct keyring_list *klist = keyring->payload.subscriptions;
+       struct keyring_list *klist;
+
+       klist = rcu_dereference_locked_keyring(keyring);
 
        /* adjust the quota */
        key_payload_reserve(keyring, 0);
@@ -1024,7 +1027,7 @@ void keyring_gc(struct key *keyring, time_t limit)
 
        down_write(&keyring->sem);
 
-       klist = keyring->payload.subscriptions;
+       klist = rcu_dereference_locked_keyring(keyring);
        if (!klist)
                goto no_klist;