Re: [PATCH] memstick: r592: Fix UAF bug in r592_remove due to race condition

[Ulf Hansson]

On Tue, 7 Mar 2023 at 17:44, Zheng Wang <zyytlz.wz@xxxxxxx> wrote:
>
> In r592_probe, dev->detect_timer was bound with r592_detect_timer.
> In r592_irq function, the timer function will be invoked by mod_timer.
>
> If we remove the module which will call hantro_release to make cleanup,
> there may be a unfinished work. The possible sequence is as follows,
> which will cause a typical UAF bug.
>
> Fix it by canceling the work before cleanup in r592_remove.
>
> CPU0                  CPU1
>
>                     |r592_detect_timer
> r592_remove         |
>   memstick_free_host|
>   put_device;       |
>   kfree(host);      |
>                     |
>                     | queue_work
>                     |   &host->media_checker //use
>
> Signed-off-by: Zheng Wang <zyytlz.wz@xxxxxxx>

Applied for next, thanks!

Kind regards
Uffe


> ---
>  drivers/memstick/host/r592.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/memstick/host/r592.c b/drivers/memstick/host/r592.c
> index 1d35d147552d..2bfa7eaae80a 100644
> --- a/drivers/memstick/host/r592.c
> +++ b/drivers/memstick/host/r592.c
> @@ -829,7 +829,7 @@ static void r592_remove(struct pci_dev *pdev)
>         /* Stop the processing thread.
>         That ensures that we won't take any more requests */
>         kthread_stop(dev->io_thread);
> -
> +       del_timer_sync(&dev->detect_timer);
>         r592_enable_device(dev, false);
>
>         while (!error && dev->req) {
> --
> 2.25.1
>