netfilter: exit_net cleanup check added

Be sure that lists initialized in net_init hook was return to initial
state.

Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index a77dd51..55802e9 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1729,8 +1729,17 @@ static int __net_init xt_net_init(struct net *net)
 	return 0;
 }
 
+static void __net_exit xt_net_exit(struct net *net)
+{
+	int i;
+
+	for (i = 0; i < NFPROTO_NUMPROTO; i++)
+		WARN_ON_ONCE(!list_empty(&net->xt.tables[i]));
+}
+
 static struct pernet_operations xt_net_ops = {
 	.init = xt_net_init,
+	.exit = xt_net_exit,
 };
 
 static int __init xt_init(void)