!1428 scsi: iscsi_tcp: Check that sock is valid before iscsi_set_param()

Merge Pull Request from: @ci-robot 
 
PR sync from: Zhong Jinghua <zhongjinghua@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/2Q2MUBDGYX4ZZCIKBMR4GVCYTRF6GIG7/ 
 
https://gitee.com/openeuler/kernel/issues/I7L8DZ?from=project-issue 
 
Link:https://gitee.com/openeuler/kernel/pulls/1428 

Reviewed-by: Yu Kuai <yukuai3@huawei.com> 
Reviewed-by: Jialin Zhang <zhangjialin11@huawei.com> 
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com> 

drivers/scsi/iscsi_tcp.c

@@ -729,13 +729,12 @@ static int iscsi_sw_tcp_conn_set_param(struct iscsi_cls_conn *cls_conn,
 		iscsi_set_param(cls_conn, param, buf, buflen);
 		break;
 	case ISCSI_PARAM_DATADGST_EN:
-		iscsi_set_param(cls_conn, param, buf, buflen);
-
 		mutex_lock(&tcp_sw_conn->sock_lock);
 		if (!tcp_sw_conn->sock) {
 			mutex_unlock(&tcp_sw_conn->sock_lock);
 			return -ENOTCONN;
 		}
+		iscsi_set_param(cls_conn, param, buf, buflen);
 		tcp_sw_conn->sendpage = conn->datadgst_en ?
 			sock_no_sendpage : tcp_sw_conn->sock->ops->sendpage;
 		mutex_unlock(&tcp_sw_conn->sock_lock);