netfilter: cttimeout: decouple unlink and free on netns destruction

Increment the extid on module removal; this makes sure that even
in extreme cases any old uncofirmed entry that happened to be kept
e.g. on nfnetlink_queue list will not trip over a stale timeout
reference.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nfnetlink_cttimeout.c

@@ -656,12 +656,24 @@ static int __init cttimeout_init(void)
 	return ret;
 }
 
+static int untimeout(struct nf_conn *ct, void *timeout)
+{
+	struct nf_conn_timeout *timeout_ext = nf_ct_timeout_find(ct);
+
+	if (timeout_ext)
+		RCU_INIT_POINTER(timeout_ext->timeout, NULL);
+
+	return 0;
+}
+
 static void __exit cttimeout_exit(void)
 {
 	nfnetlink_subsys_unregister(&cttimeout_subsys);
 
 	unregister_pernet_subsys(&cttimeout_ops);
 	RCU_INIT_POINTER(nf_ct_timeout_hook, NULL);
+
+	nf_ct_iterate_destroy(untimeout, NULL);
 	synchronize_rcu();
 }