netfilter: nfnetlink: fix missing rcu_read_unlock in nfnetlink_rcv_msg

Bug added in commit 6b75e3e8d6 (netfilter: nfnetlink: add RCU in
nfnetlink_rcv_msg())

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nfnetlink.c

@@ -169,8 +169,10 @@ replay:
 
 		err = nla_parse(cda, ss->cb[cb_id].attr_count,
 				attr, attrlen, ss->cb[cb_id].policy);
-		if (err < 0)
+		if (err < 0) {
+			rcu_read_unlock();
 			return err;
+		}
 
 		if (nc->call_rcu) {
 			err = nc->call_rcu(net->nfnl, skb, nlh,