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| author | Sabrina Dubroca <sd@queasysnail.net> | 2017-09-26 16:16:43 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-09-26 10:24:34 -0700 |
| commit | 62b982eeb4589b2e6d7c01a90590e3a4c2b2ca19 (patch) | |
| tree | 49dabd03d76177db735d196ecf9883191d6ac5cc /net/l2tp/l2tp_core.c | |
| parent | 36f6ee22d2d66046e369757ec6bbe1c482957ba6 (diff) | |
| download | linux-62b982eeb4589b2e6d7c01a90590e3a4c2b2ca19.tar.bz2 | |
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
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>
Diffstat (limited to 'net/l2tp/l2tp_core.c')
| -rw-r--r-- | net/l2tp/l2tp_core.c | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c index d8c2a89a76e1..02d61101b108 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -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) { - 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); |