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    Subject[PATCH 3.13.y-ckt 49/96] l2tp: protect tunnel->del_work by ref_count
    Date
    3.13.11-ckt30 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Alexander Couzens <lynxis@fe80.eu>

    [ Upstream commit 06a15f51cf3618e32a73871ee6a547ef7fd902b5 ]

    There is a small chance that tunnel_free() is called before tunnel->del_work scheduled
    resulting in a zero pointer dereference.

    Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
    Acked-by: James Chapman <jchapman@katalix.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    net/l2tp/l2tp_core.c | 11 +++++++++--
    1 file changed, 9 insertions(+), 2 deletions(-)

    diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
    index 9af77d9..670220d 100644
    --- a/net/l2tp/l2tp_core.c
    +++ b/net/l2tp/l2tp_core.c
    @@ -1438,7 +1438,7 @@ static void l2tp_tunnel_del_work(struct work_struct *work)
    tunnel = container_of(work, struct l2tp_tunnel, del_work);
    sk = l2tp_tunnel_sock_lookup(tunnel);
    if (!sk)
    - return;
    + goto out;

    sock = sk->sk_socket;

    @@ -1459,6 +1459,8 @@ static void l2tp_tunnel_del_work(struct work_struct *work)
    }

    l2tp_tunnel_sock_put(sk);
    +out:
    + l2tp_tunnel_dec_refcount(tunnel);
    }

    /* Create a socket for the tunnel, if one isn't set up by
    @@ -1788,8 +1790,13 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
    */
    int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
    {
    + l2tp_tunnel_inc_refcount(tunnel);
    l2tp_tunnel_closeall(tunnel);
    - return (false == queue_work(l2tp_wq, &tunnel->del_work));
    + if (false == queue_work(l2tp_wq, &tunnel->del_work)) {
    + l2tp_tunnel_dec_refcount(tunnel);
    + return 1;
    + }
    + return 0;
    }
    EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);

    --
    1.9.1


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