[PATCH v2] netfilter: conntrack: fix wrong ct->timeout value

[Tzung-Bi Shih <tzungbi@kernel.org>]

(struct nf_conn)->timeout is an interval before the conntrack
confirmed.  After confirmed, it becomes a timestamp[1].

It is observed that timeout of an unconfirmed conntrack have been
altered by calling ctnetlink_change_timeout().  As a result,
`nfct_time_stamp` was wrongly added to `ct->timeout` twice[2].

Skip changing timeout if the conntrack is unconfirmed.

[1]: https://elixir.bootlin.com/linux/v6.3-rc5/source/net/netfilter/nf_conntrack_core.c#L1257
[2]: https://elixir.bootlin.com/linux/v6.3-rc5/source/include/net/netfilter/nf_conntrack_core.h#L92

Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
---
Changes from v1 (https://lore.kernel.org/netfilter-devel/20230410060935.253503-1-tzungbi@kernel.org/T/#u):
- Just skip updating if the conntrack is unconfirmed per review comment.

 net/netfilter/nf_conntrack_netlink.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index fbc47e4b7bc3..f5abea20774c 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1986,6 +1986,10 @@ static int ctnetlink_change_helper(struct nf_conn *ct,
 static int ctnetlink_change_timeout(struct nf_conn *ct,
 				    const struct nlattr * const cda[])
 {
+	/* skip changing timeout if the conntrack is unconfirmed */
+	if (!nf_ct_is_confirmed(ct))
+		return 0;
+
 	return __nf_ct_change_timeout(ct, (u64)ntohl(nla_get_be32(cda[CTA_TIMEOUT])) * HZ);
 }
 
-- 
2.40.0.577.gac1e443424-goog