Input: byd - synchronize timer deletion before freeing private data

[ Upstream commit c83e79c ]

byd_disconnect() uses timer_delete() before freeing the driver's private
data.  This does not wait for a running byd_clear_touch() callback, which
dereferences the private data and its psmouse pointer.  A callback racing
with disconnect can therefore access the private data after it has been
freed.  The timer can also still be re-armed by byd_process_byte() while
the disconnect is in progress.

Use timer_shutdown_sync() before freeing the private data: it waits for
a running callback and turns any later re-arm attempt into a no-op.

Fixes: 2d5f561 ("Input: byd - enable absolute mode")
Cc: stable@vger.kernel.org
Signed-off-by: Linmao Li <lilinmao@kylinos.cn>
Link: https://patch.msgid.link/20260720061259.1601281-1-lilinmao@kylinos.cn
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
[ changed `del_timer()` to `timer_shutdown_sync()` since 6.12 predates the `del_timer()` → `timer_delete()` rename ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Linmao Li

drivers/input/mouse/byd.c

@@ -426,7 +426,7 @@ static void byd_disconnect(struct psmouse *psmouse)
 	struct byd_data *priv = psmouse->private;
 
 	if (priv) {
-		del_timer(&priv->timer);
+		timer_shutdown_sync(&priv->timer);
 		kfree(psmouse->private);
 		psmouse->private = NULL;
 	}