[NETFILTER]: nfnetlink_log: fix possible NULL pointer dereference

Eliminate possible NULL pointer dereference in nfulnl_recv_config().
Signed-off-by: Michal Miroslaw <mirq-linux@rere.qmqm.pl>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nfnetlink_log.c

@@ -858,6 +858,9 @@ nfulnl_recv_config(struct sock *ctnl, struct sk_buff *skb,
 			ret = -EINVAL;
 			break;
 		}
+
+		if (!inst)
+			goto out;
 	} else {
 		if (!inst) {
 			UDEBUG("no config command, and no instance for "
@@ -911,6 +914,7 @@ nfulnl_recv_config(struct sock *ctnl, struct sk_buff *skb,
 
 out_put:
 	instance_put(inst);
+out:
 	return ret;
 }