[PATCH v2] xirc2ps_cs: Fix use after free bug in xirc2ps_detach

[Zheng Wang]

In xirc2ps_probe, the local->tx_timeout_task was bounded
with xirc2ps_tx_timeout_task. When timeout occurs,
it will call xirc_tx_timeout->schedule_work to start the
work.

When we call xirc2ps_detach to remove the driver, there
may be a sequence as follows:

Stop responding to timeout tasks and complete scheduled
tasks before cleanup in xirc2ps_detach, which will fix
the problem.

CPU0                  CPU1

                    |xirc2ps_tx_timeout_task
xirc2ps_detach      |
  free_netdev       |
    kfree(dev);     |
                    |
                    | do_reset
                    |   //use dev

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Zheng Wang <zyytlz.wz@xxxxxxx>
---
v2:
- fix indentation error suggested by Simon Horman,
and stop the timeout tasks  suggested by Yunsheng Lin
---
 drivers/net/ethernet/xircom/xirc2ps_cs.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/xircom/xirc2ps_cs.c b/drivers/net/ethernet/xircom/xirc2ps_cs.c
index 894e92ef415b..c77ca11d9497 100644
--- a/drivers/net/ethernet/xircom/xirc2ps_cs.c
+++ b/drivers/net/ethernet/xircom/xirc2ps_cs.c
@@ -503,6 +503,11 @@ static void
 xirc2ps_detach(struct pcmcia_device *link)
 {
     struct net_device *dev = link->priv;
+		struct local_info *local = netdev_priv(dev);
+
+		netif_carrier_off(dev);
+		netif_tx_disable(dev);
+		cancel_work_sync(&local->tx_timeout_task);
 
     dev_dbg(&link->dev, "detach\n");
 
-- 
2.25.1