Re: [PATCH] Input: cyttsp4_core - change del_timer_sync() to timer_shutdown_sync()

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Sep 08, 2023 at 05:41:35AM +0400, Denis Efremov (Oracle) wrote:
> From: Duoming Zhou <duoming@zju.edu.cn>
> 
> The watchdog_timer can schedule tx_timeout_task and watchdog_work
> can also arm watchdog_timer. The process is shown below:
> 
> ----------- timer schedules work ------------
> cyttsp4_watchdog_timer() //timer handler
>   schedule_work(&cd->watchdog_work)
> 
> ----------- work arms timer ------------
> cyttsp4_watchdog_work() //workqueue callback function
>   cyttsp4_start_wd_timer()
>     mod_timer(&cd->watchdog_timer, ...)
> 
> Although del_timer_sync() and cancel_work_sync() are called in
> cyttsp4_remove(), the timer and workqueue could still be rearmed.
> As a result, the possible use after free bugs could happen. The
> process is shown below:
> 
>   (cleanup routine)           |  (timer and workqueue routine)
> cyttsp4_remove()              | cyttsp4_watchdog_timer() //timer
>   cyttsp4_stop_wd_timer()     |   schedule_work()
>     del_timer_sync()          |
>                               | cyttsp4_watchdog_work() //worker
>                               |   cyttsp4_start_wd_timer()
>                               |     mod_timer()
>     cancel_work_sync()        |
>                               | cyttsp4_watchdog_timer() //timer
>                               |   schedule_work()
>     del_timer_sync()          |
>   kfree(cd) //FREE            |
>                               | cyttsp4_watchdog_work() // reschedule!
>                               |   cd-> //USE
> 
> This patch changes del_timer_sync() to timer_shutdown_sync(),
> which could prevent rearming of the timer from the workqueue.
> 
> Cc: stable@vger.kernel.org
> Fixes: CVE-2023-4134

"CVE" is not a valid Fixes tag :(

> Fixes: 17fb1563d69b ("Input: cyttsp4 - add core driver for Cypress TMA4XX touchscreen devices")
> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
> Link: https://lore.kernel.org/r/20230421082919.8471-1-duoming@zju.edu.cn
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Signed-off-by: Denis Efremov (Oracle) <efremov@linux.com>
> ---
> 
> I've only added Cc: stable and Fixes tag.

What is the commit id in Linus's tree for this?

thanks,

greg k-h