netfilter, bpf: Adjust timeouts of non-confirmed CTs in bpf_ct_insert_entry()

jira VULN-430
cve-bf CVE-2023-4244
commit-author Ilya Leoshkevich <iii@linux.ibm.com>
commit 837723b

bpf_nf testcase fails on s390x: bpf_skb_ct_lookup() cannot find the entry
that was added by bpf_ct_insert_entry() within the same BPF function.

The reason is that this entry is deleted by nf_ct_gc_expired().

The CT timeout starts ticking after the CT confirmation; therefore
nf_conn.timeout is initially set to the timeout value, and
__nf_conntrack_confirm() sets it to the deadline value.

bpf_ct_insert_entry() sets IPS_CONFIRMED_BIT, but does not adjust the
timeout, making its value meaningless and causing false positives.

Fix the problem by making bpf_ct_insert_entry() adjust the timeout,
like __nf_conntrack_confirm().

Fixes: 2cdaa3e ("netfilter: conntrack: restore IPS_CONFIRMED out of nf_conntrack_hash_check_insert()")
	Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
	Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
	Cc: Florian Westphal <fw@strlen.de>
Link: https://lore.kernel.org/bpf/20230830011128.1415752-3-iii@linux.ibm.com
	Signed-off-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit 837723b)
	Signed-off-by: Marcin Wcisło <marcin.wcislo@conclusive.pl>

Author: pvts-mat

net/netfilter/nf_conntrack_bpf.c

@@ -339,6 +339,8 @@ struct nf_conn *bpf_ct_insert_entry(struct nf_conn___init *nfct_i)
 	struct nf_conn *nfct = (struct nf_conn *)nfct_i;
 	int err;
 
+	if (!nf_ct_is_confirmed(nfct))
+		nfct->timeout += nfct_time_stamp;
 	nfct->status |= IPS_CONFIRMED;
 	err = nf_conntrack_hash_check_insert(nfct);
 	if (err < 0) {