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

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

[Marcelo Ricardo Leitner]

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@strlen.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@gmail.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

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

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Thu, 24 Mar 2022 16:22:10 -0300 you wrote:
> 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().
> 
> [...]

Here is the summary with links:
  - [net] net/sched: act_ct: fix ref leak when switching zones
    https://git.kernel.org/netdev/net/c/bcb74e132a76

You are awesome, thank you!
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