Commit 2f86953e authored Sep 02, 2016 by Sabrina Dubroca Committed by David S. Miller Sep 02, 2016

l2tp: fix use-after-free during module unload



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: 167eb17e ("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>

parent ab343801

net/l2tp/l2tp_core.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -1855,6 +1855,9 @@ static __net_exit void l2tp_exit_net(struct net *net)
		(void)l2tp_tunnel_delete(tunnel);
		}
		rcu_read_unlock_bh();

		flush_workqueue(l2tp_wq);
		rcu_barrier();
		}

		static struct pernet_operations l2tp_net_ops = {

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