[PATCH 6.12 098/567] Input: lkkbd - disable pending work before freeing device

Greg Kroah-Hartman
2026-01-06T17:19:44Z

From: Minseong Kim <ii4gsp@gmail.com>

commit e58c88f0cb2d8ed89de78f6f17409d29cfab6c5c upstream.

lkkbd_interrupt() schedules lk->tq via schedule_work(), and the work
handler lkkbd_reinit() dereferences the lkkbd structure and its
serio/input_dev fields.

lkkbd_disconnect() and error paths in lkkbd_connect() free the lkkbd
structure without preventing the reinit work from being queued again
until serio_close() returns. This can allow the work handler to run
after the structure has been freed, leading to a potential use-after-free.

Use disable_work_sync() instead of cancel_work_sync() to ensure the
reinit work cannot be re-queued, and call it both in lkkbd_disconnect()
and in lkkbd_connect() error paths after serio_open().

Signed-off-by: Minseong Kim <ii4gsp@gmail.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20251212052314.16139-1-ii4gsp@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/input/keyboard/lkkbd.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/input/keyboard/lkkbd.c
+++ b/drivers/input/keyboard/lkkbd.c
@@ -670,7 +670,8 @@ static int lkkbd_connect(struct serio *s

return 0;

- fail3: serio_close(serio);
+ fail3: disable_work_sync(&lk->tq);
+ serio_close(serio);
fail2: serio_set_drvdata(serio, NULL);
fail1: input_free_device(input_dev);
kfree(lk);
@@ -684,6 +685,8 @@ static void lkkbd_disconnect(struct seri
{
struct lkkbd *lk = serio_get_drvdata(serio);

+ disable_work_sync(&lk->tq);
+
input_get_device(lk->dev);
input_unregister_device(lk->dev);
serio_close(serio);