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

[Simon Horman <simon.horman@corigine.com>]

On Fri, Mar 10, 2023 at 12:57:29AM +0800, Zheng Wang wrote:
> 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:
> 
> Fix it by finishing the work before cleanup in xirc2ps_detach
> 
> CPU0                  CPU1
> 
>                     |xirc2ps_tx_timeout_task
> xirc2ps_detach      |
>   free_netdev       |
>     kfree(dev);     |
>                     |
>                     | do_reset
>                     |   //use
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> ---
>  drivers/net/ethernet/xircom/xirc2ps_cs.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/xircom/xirc2ps_cs.c b/drivers/net/ethernet/xircom/xirc2ps_cs.c
> index 894e92ef415b..ea7b06f75691 100644
> --- a/drivers/net/ethernet/xircom/xirc2ps_cs.c
> +++ b/drivers/net/ethernet/xircom/xirc2ps_cs.c
> @@ -503,7 +503,10 @@ static void
>  xirc2ps_detach(struct pcmcia_device *link)
>  {
>      struct net_device *dev = link->priv;
> -
> +		struct local_info *local;
> +
> +		local = netdev_priv(dev);
> +		cancel_work_sync(&local->tx_timeout_task)
>      dev_dbg(&link->dev, "detach\n");
>  
>      unregister_netdev(dev);

This doesn't compile.
Also, the indentation is incorrect.

I think what should have been posted is:

diff --git a/drivers/net/ethernet/xircom/xirc2ps_cs.c b/drivers/net/ethernet/xircom/xirc2ps_cs.c
index 894e92ef415b..b607fea486ab 100644
--- a/drivers/net/ethernet/xircom/xirc2ps_cs.c
+++ b/drivers/net/ethernet/xircom/xirc2ps_cs.c
@@ -503,7 +503,10 @@ static void
 xirc2ps_detach(struct pcmcia_device *link)
 {
     struct net_device *dev = link->priv;
+    struct local_info *local;
 
+    local = netdev_priv(dev);
+    cancel_work_sync(&local->tx_timeout_task);
     dev_dbg(&link->dev, "detach\n");
 
     unregister_netdev(dev);