Commit 62b982ee authored by Sabrina Dubroca's avatar Sabrina Dubroca Committed by David S. Miller

l2tp: fix race condition in l2tp_tunnel_delete

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

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.


    ip l2tp add tunnel tunnel_id 3000 peer_tunnel_id 4000 local remote 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: f8ccac0e ("l2tp: put tunnel socket release on a workqueue")
Reported-by: default avatarJianlin Shi <>
Signed-off-by: default avatarSabrina Dubroca <>
Acked-by: default avatarGuillaume Nault <>
Signed-off-by: default avatarDavid S. Miller <>
parent 36f6ee22
......@@ -1688,14 +1688,12 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
/* 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)
if (false == queue_work(l2tp_wq, &tunnel->del_work)) {
return 1;
if (!test_and_set_bit(0, &tunnel->dead)) {
queue_work(l2tp_wq, &tunnel->del_work);
return 0;
......@@ -161,6 +161,9 @@ struct l2tp_tunnel_cfg {
struct l2tp_tunnel {
int magic; /* Should be L2TP_TUNNEL_MAGIC */
unsigned long dead;
struct rcu_head rcu;
rwlock_t hlist_lock; /* protect session_hlist */
bool acpt_newsess; /* Indicates whether this
......@@ -255,7 +258,7 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id,
u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
struct l2tp_tunnel **tunnelp);
void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
struct l2tp_session *l2tp_session_create(int priv_size,
struct l2tp_tunnel *tunnel,
u32 session_id, u32 peer_session_id,
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