l2tp: fix race condition in l2tp_tunnel_delete
[ Upstream commit 62b982eeb4589b2e6d7c01a90590e3a4c2b2ca19 ]
If we try to delete the same tunnel twice, the first delete operation
does a lookup (l2tp_tunnel_get), finds the tunnel, calls
l2tp_tunnel_delete, which queues it for deletion by
l2tp_tunnel_del_work.
The second delete operation also finds the tunnel and calls
l2tp_tunnel_delete. If the workqueue has already fired and started
running l2tp_tunnel_del_work, then l2tp_tunnel_delete will queue the
same tunnel a second time, and try to free the socket again.
Add a dead flag to prevent firing the workqueue twice. Then we can
remove the check of queue_work's result that was meant to prevent that
race but doesn't.
Reproducer:
ip l2tp add tunnel tunnel_id 3000 peer_tunnel_id 4000 local 192.168.0.2 remote 192.168.0.1 encap udp udp_sport 5000 udp_dport 6000
ip l2tp add session name l2tp1 tunnel_id 3000 session_id 1000 peer_session_id 2000
ip link set l2tp1 up
ip l2tp del tunnel tunnel_id 3000
ip l2tp del tunnel tunnel_id 3000
Fixes: f8ccac0e4493 ("l2tp: put tunnel socket release on a workqueue")
Reported-by: Jianlin Shi <jishi@redhat.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Acked-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 3415e20..b06acd0 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1737,14 +1737,12 @@
/* This function is used by the netlink TUNNEL_DELETE command.
*/
-int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
+void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
{
- l2tp_tunnel_inc_refcount(tunnel);
- if (false == queue_work(l2tp_wq, &tunnel->del_work)) {
- l2tp_tunnel_dec_refcount(tunnel);
- return 1;
+ if (!test_and_set_bit(0, &tunnel->dead)) {
+ l2tp_tunnel_inc_refcount(tunnel);
+ queue_work(l2tp_wq, &tunnel->del_work);
}
- return 0;
}
EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);