netfilter: ipset: Fix rename concurrency with listing

Shijie Luo reported that when stress-testing ipset with multiple concurrent
create, rename, flush, list, destroy commands, it can result

ipset <version>: Broken LIST kernel message: missing DATA part!

error messages and broken list results. The problem was the rename operation
was not properly handled with respect of listing. The patch fixes the issue.
Reported-by: Shijie Luo <luoshijie1@huawei.com>
Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>

net/netfilter/ipset/ip_set_core.c

@@ -1161,7 +1161,7 @@ static int ip_set_rename(struct net *net, struct sock *ctnl,
 		return -ENOENT;
 
 	write_lock_bh(&ip_set_ref_lock);
-	if (set->ref != 0) {
+	if (set->ref != 0 || set->ref_netlink != 0) {
 		ret = -IPSET_ERR_REFERENCED;
 		goto out;
 	}