nbd:fix memory leak in nbd_get_socket()

Before returning NULL, put the sock first.

Cc: [email protected]
Fixes: cf1b232 ("nbd: verify socket is supported during setup")
Reviewed-by: Josef Bacik <[email protected]>
Reviewed-by: Mike Christie <[email protected]>
Signed-off-by: Sun Ke <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: sunke-lp

drivers/block/nbd.c

@@ -993,6 +993,7 @@ static struct socket *nbd_get_socket(struct nbd_device *nbd, unsigned long fd,
 	if (sock->ops->shutdown == sock_no_shutdown) {
 		dev_err(disk_to_dev(nbd->disk), "Unsupported socket: shutdown callout must be supported.\n");
 		*err = -EINVAL;
+		sockfd_put(sock);
 		return NULL;
 	}