diff mbox series

[4.4,284/312] l2tp: fix use-after-free during module unload

Message ID 20200508123144.376454291@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH May 8, 2020, 12:34 p.m. UTC 
From: Sabrina Dubroca <sd@queasysnail.net>

commit 2f86953e7436c9b9a4690909c5e2db24799e173b upstream.

Tunnel deletion is delayed by both a workqueue (l2tp_tunnel_delete -> wq
 -> l2tp_tunnel_del_work) and RCU (sk_destruct -> RCU ->
l2tp_tunnel_destruct).

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 <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/l2tp/l2tp_core.c |    3 +++
 1 file changed, 3 insertions(+)
diff mbox series

Patch

--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1953,6 +1953,9 @@  static __net_exit void l2tp_exit_net(str
 		l2tp_tunnel_delete(tunnel);
 	}
 	rcu_read_unlock_bh();
+
+	flush_workqueue(l2tp_wq);
+	rcu_barrier();
 }
 
 static struct pernet_operations l2tp_net_ops = {