[PATCH 5.0 07/32] l2tp: use rcu_dereference_sk_user_data() in l2tp_udp_encap_recv()

Greg Kroah-Hartman
2019-05-04T10:26:55Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit c1c477217882c610a2ba0268f5faf36c9c092528 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/l2tp/l2tp_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- 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 l2tp_tunnel *tunnel;

- tunnel = l2tp_tunnel(sk);
+ tunnel = rcu_dereference_sk_user_data(sk);
if (tunnel == NULL)
goto pass_up;