!3391 nbd_genl_status: null check for nla_nest_start

Merge Pull Request from: @ci-robot 
 
PR sync from: Yuan Can <yuancan@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/XWQZF664UIDOOLI6QTN43ZLLEIQIF3TF/ 
 
https://gitee.com/openeuler/kernel/issues/I8NC0E 
 
Link:https://gitee.com/openeuler/kernel/pulls/3391

 

Reviewed-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>