netfilter: ctnetlink: fix missing locking while changing conntrack from nfqueue

Since 9cb01766 netfilter: add glue code to integrate nfnetlink_queue and
ctnetlink, we can modify the conntrack entry via nfnl_queue. However, the
change of the conntrack entry via nfnetlink_queue requires appropriate
locking to avoid concurrent updates.
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_netlink.c

@@ -1896,10 +1896,15 @@ static int
 ctnetlink_nfqueue_parse(const struct nlattr *attr, struct nf_conn *ct)
 {
 	struct nlattr *cda[CTA_MAX+1];
+	int ret;
 
 	nla_parse_nested(cda, CTA_MAX, attr, ct_nla_policy);
 
-	return ctnetlink_nfqueue_parse_ct((const struct nlattr **)cda, ct);
+	spin_lock_bh(&nf_conntrack_lock);
+	ret = ctnetlink_nfqueue_parse_ct((const struct nlattr **)cda, ct);
+	spin_unlock_bh(&nf_conntrack_lock);
+
+	return ret;
 }
 
 static struct nfq_ct_hook ctnetlink_nfqueue_hook = {