From: Eric Dumazet <edumazet@google.com>
Date: Tue, 23 Apr 2019 16:43:26 +0000 (-0700)
Subject: l2tp: use rcu_dereference_sk_user_data() in l2tp_udp_encap_recv()
X-Git-Tag: v5.1~11^2~32
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=c1c477217882c610a2ba0268f5faf36c9c092528;p=users%2Fhch%2Fblock.git

l2tp: use rcu_dereference_sk_user_data() in l2tp_udp_encap_recv()

Canonical way to fetch sk_user_data from an encap_rcv() handler called
from UDP stack in rcu protected section is to use rcu_dereference_sk_user_data(),
otherwise compiler might read it multiple times.

Fixes: d00fa9adc528 ("il2tp: fix races with tunnel socket close")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index fed6becc5daf..aee33d132018 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -909,7 +909,7 @@ int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct l2tp_tunnel *tunnel;
 
-	tunnel = l2tp_tunnel(sk);
+	tunnel = rcu_dereference_sk_user_data(sk);
 	if (tunnel == NULL)
 		goto pass_up;