[PATCH 6.12 099/567] Input: alps - fix use-after-free bugs caused by dev3_register_work

Greg Kroah-Hartman
2026-01-06T17:19:48Z

From: Duoming Zhou <duoming@zju.edu.cn>

commit bf40644ef8c8a288742fa45580897ed0e0289474 upstream.

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@kernel.org
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://patch.msgid.link/b57b0a9ccca51a3f06be141bfc02b9ffe69d1845.1765939397.git.duoming@zju.edu.cn
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/input/mouse/alps.c | 1 +
1 file changed, 1 insertion(+)

--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -2977,6 +2977,7 @@ static void alps_disconnect(struct psmou

psmouse_reset(psmouse);
timer_shutdown_sync(&priv->timer);
+ disable_delayed_work_sync(&priv->dev3_register_work);
if (priv->dev2)
input_unregister_device(priv->dev2);
if (!IS_ERR_OR_NULL(priv->dev3))