netdev - [PATCH net] net/sched: act_ct: fix ref leak when switching zones

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Message-Id: <9925b0003629c6f3421f6b36819fa1edabd44f4f.1648149598.git.marcelo.leitner@gmail.com>
Date:   Thu, 24 Mar 2022 16:22:10 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     netdev@...r.kernel.org
Cc:     Florian Westphal <fw@...len.de>, Paul Blakey <paulb@...dia.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>
Subject: [PATCH net] net/sched: act_ct: fix ref leak when switching zones

When switching zones or network namespaces without doing a ct clear in
between, it is now leaking a reference to the old ct entry. That's
because tcf_ct_skb_nfct_cached() returns false and
tcf_ct_flow_table_lookup() may simply overwrite it.

The fix is to, as the ct entry is not reusable, free it already at
tcf_ct_skb_nfct_cached().

Reported-by: Florian Westphal <fw@...len.de>
Fixes: 2f131de361f6 ("net/sched: act_ct: Fix flow table lookup after ct clear or switching zones")
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
---
 net/sched/act_ct.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
index ec19f625863a04229a9a3894a423e6dd562844a1..25718acc0ff00178fa42d6169d930351e565b104 100644
--- a/net/sched/act_ct.c
+++ b/net/sched/act_ct.c
@@ -605,22 +605,25 @@ static bool tcf_ct_skb_nfct_cached(struct net *net, struct sk_buff *skb,
 	if (!ct)
 		return false;
 	if (!net_eq(net, read_pnet(&ct->ct_net)))
-		return false;
+		goto drop_ct;
 	if (nf_ct_zone(ct)->id != zone_id)
-		return false;
+		goto drop_ct;
 
 	/* Force conntrack entry direction. */
 	if (force && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
 		if (nf_ct_is_confirmed(ct))
 			nf_ct_kill(ct);
 
-		nf_ct_put(ct);
-		nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
-
-		return false;
+		goto drop_ct;
 	}
 
 	return true;
+
+drop_ct:
+	nf_ct_put(ct);
+	nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
+
+	return false;
 }
 
 /* Trim the skb to the length specified by the IP/IPv6 header,
-- 
2.35.1