Re: [PATCH v2 RESEND 1/2] Input: alps - fix use-after-free bugs caused by dev3_register_work

[Dmitry Torokhov]

On Wed, Dec 17, 2025 at 11:00:17AM +0800, Duoming Zhou wrote:
> The dev3_register_work delayed work item is initialized within
> alps_reconnect() and scheduled upon receipt of the first bare
> PS/2 packet from an external PS/2 device connected to the ALPS
> touchpad. During device detachment, the original implementation
> calls flush_workqueue() in psmouse_disconnect() to ensure
> completion of dev3_register_work. However, the flush_workqueue()
> in psmouse_disconnect() only blocks and waits for work items that
> were already queued to the workqueue prior to its invocation. Any
> work items submitted after flush_workqueue() is called are not
> included in the set of tasks that the flush operation awaits.
> This means that after flush_workqueue() has finished executing,
> the dev3_register_work could still be scheduled. Although the
> psmouse state is set to PSMOUSE_CMD_MODE in psmouse_disconnect(),
> the scheduling of dev3_register_work remains unaffected.
> 
> The race condition can occur as follows:
> 
> CPU 0 (cleanup path)     | CPU 1 (delayed work)
> psmouse_disconnect()     |
>   psmouse_set_state()    |
>   flush_workqueue()      | alps_report_bare_ps2_packet()
>   alps_disconnect()      |   psmouse_queue_work()
>     kfree(priv); // FREE | alps_register_bare_ps2_mouse()
>                          |   priv = container_of(work...); // USE
>                          |   priv->dev3 // USE
> 
> Add disable_delayed_work_sync() in alps_disconnect() to ensure
> that dev3_register_work is properly canceled and prevented from
> executing after the alps_data structure has been deallocated.
> 
> This bug is identified by static analysis.
> 
> Fixes: 04aae283ba6a ("Input: ALPS - do not mix trackstick and external PS/2 mouse data")
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>

Applied, thank you.

-- 
Dmitry