blob: 040e5976b1984205725361385171afb0b1f66fc5 [file] [log] [blame]
From: Sabrina Dubroca <>
Date: Fri, 2 Sep 2016 10:22:54 +0200
Subject: l2tp: fix use-after-free during module unload
commit 2f86953e7436c9b9a4690909c5e2db24799e173b upstream.
Tunnel deletion is delayed by both a workqueue (l2tp_tunnel_delete -> wq
-> l2tp_tunnel_del_work) and RCU (sk_destruct -> RCU ->
By the time l2tp_tunnel_destruct() runs to destroy the tunnel and finish
destroying the socket, the private data reserved via the net_generic
mechanism has already been freed, but l2tp_tunnel_destruct() actually
uses this data.
Make sure tunnel deletion for the netns has completed before returning
from l2tp_exit_net() by first flushing the tunnel removal workqueue, and
then waiting for RCU callbacks to complete.
Fixes: 167eb17e0b17 ("l2tp: create tunnel sockets in the right namespace")
Signed-off-by: Sabrina Dubroca <>
Signed-off-by: David S. Miller <>
Signed-off-by: Ben Hutchings <>
net/l2tp/l2tp_core.c | 3 +++
1 file changed, 3 insertions(+)
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1892,6 +1892,9 @@ static __net_exit void l2tp_exit_net(str
+ flush_workqueue(l2tp_wq);
+ rcu_barrier();
static struct pernet_operations l2tp_net_ops = {