netfilter: conntrack: restore IPS_CONFIRMED out of nf_conntrack_hash_check_insert()

e6d57e9ff0 ("netfilter: conntrack: fix rmmod double-free race")
consolidates IPS_CONFIRMED bit set in nf_conntrack_hash_check_insert().
However, this breaks ctnetlink:

 # conntrack -I -p tcp --timeout 123 --src 1.2.3.4 --dst 5.6.7.8 --state ESTABLISHED --sport 1 --dport 4 -u SEEN_REPLY
 conntrack v1.4.6 (conntrack-tools): Operation failed: Device or resource busy

This is a partial revert of the aforementioned commit to restore
IPS_CONFIRMED.

Fixes: e6d57e9ff0 ("netfilter: conntrack: fix rmmod double-free race")
Reported-by: Stéphane Graber <stgraber@stgraber.org>
Tested-by: Stéphane Graber <stgraber@stgraber.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_bpf.c

@@ -381,6 +381,7 @@ __bpf_kfunc struct nf_conn *bpf_ct_insert_entry(struct nf_conn___init *nfct_i)
 	struct nf_conn *nfct = (struct nf_conn *)nfct_i;
 	int err;
 
+	nfct->status |= IPS_CONFIRMED;
 	err = nf_conntrack_hash_check_insert(nfct);
 	if (err < 0) {
 		nf_conntrack_free(nfct);

net/netfilter/nf_conntrack_core.c

@@ -932,7 +932,6 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct)
 		goto out;
 	}
 
-	ct->status |= IPS_CONFIRMED;
 	smp_wmb();
 	/* The caller holds a reference to this object */
 	refcount_set(&ct->ct_general.use, 2);

net/netfilter/nf_conntrack_netlink.c

@@ -2316,6 +2316,9 @@ ctnetlink_create_conntrack(struct net *net,
 	nfct_seqadj_ext_add(ct);
 	nfct_synproxy_ext_add(ct);
 
+	/* we must add conntrack extensions before confirmation. */
+	ct->status |= IPS_CONFIRMED;
+
 	if (cda[CTA_STATUS]) {
 		err = ctnetlink_change_status(ct, cda);
 		if (err < 0)