nbd: prevent memory leak

commit 03bf73c3 upstream.

In nbd_add_socket when krealloc succeeds, if nsock's allocation fail the
reallocted memory is leak. The correct behaviour should be assigning the
reallocted memory to config->socks right after success.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/block/nbd.c

@@ -984,14 +984,15 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 		sockfd_put(sock);
 		return -ENOMEM;
 	}
+
+	config->socks = socks;
+
 	nsock = kzalloc(sizeof(struct nbd_sock), GFP_KERNEL);
 	if (!nsock) {
 		sockfd_put(sock);
 		return -ENOMEM;
 	}
 
-	config->socks = socks;
-
 	nsock->fallback_index = -1;
 	nsock->dead = false;
 	mutex_init(&nsock->tx_lock);