KEYS: __key_link() should use the RCU deref wrapper for keyring payloads

__key_link() should use the RCU deref wrapper rcu_dereference_locked_keyring()
for accessing keyring payloads rather than calling rcu_dereference_protected()
directly.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

security/keys/keyring.c

@@ -860,8 +860,7 @@ void __key_link(struct key *keyring, struct key *key,
 
 	kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
 
-	klist = rcu_dereference_protected(keyring->payload.subscriptions,
-					  rwsem_is_locked(&keyring->sem));
+	klist = rcu_dereference_locked_keyring(keyring);
 
 	atomic_inc(&key->usage);