netfilter: x_tables: make sure e->next_offset covers remaining blob size

Otherwise this function may read data beyond the ruleset blob.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
static void __net_exit ip_tables_net_exit(struct net *net)
{
	xt_proto_fini(net, NFPROTO_IPV4);
}

static void __net_exit ip_tables_net_exit(struct net *net)
{
	xt_proto_fini(net, NFPROTO_IPV4);
}
