afs: Fix key refcounting in file locking code

Fix the refcounting of the authentication keys in the file locking code.
The vnode->lock_key member points to a key on which it expects to be
holding a ref, but it isn't always given an extra ref, however.

Fixes: 0fafdc9f ("afs: Fix file locking")
Signed-off-by: NDavid Howells <dhowells@redhat.com>

fs/afs/flock.c

@@ -208,7 +208,7 @@ void afs_lock_work(struct work_struct *work)
 		/* The new front of the queue now owns the state variables. */
 		next = list_entry(vnode->pending_locks.next,
 				  struct file_lock, fl_u.afs.link);
-		vnode->lock_key = afs_file_key(next->fl_file);
+		vnode->lock_key = key_get(afs_file_key(next->fl_file));
 		vnode->lock_type = (next->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
 		vnode->lock_state = AFS_VNODE_LOCK_WAITING_FOR_CB;
 		goto again;
@@ -413,7 +413,7 @@ static void afs_dequeue_lock(struct afs_vnode *vnode, struct file_lock *fl)
 	/* The new front of the queue now owns the state variables. */
 	next = list_entry(vnode->pending_locks.next,
 			  struct file_lock, fl_u.afs.link);
-	vnode->lock_key = afs_file_key(next->fl_file);
+	vnode->lock_key = key_get(afs_file_key(next->fl_file));
 	vnode->lock_type = (next->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
 	vnode->lock_state = AFS_VNODE_LOCK_WAITING_FOR_CB;
 	afs_lock_may_be_available(vnode);

fs/afs/inode.c

@@ -545,6 +545,8 @@ void afs_evict_inode(struct inode *inode)
 #endif
 
 	afs_put_permits(rcu_access_pointer(vnode->permit_cache));
+	key_put(vnode->lock_key);
+	vnode->lock_key = NULL;
 	_leave("");
 }