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SubjectRe: [PATCH net] xirc2ps_cs: Fix use after free bug in xirc2ps_detach
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);
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