[PATCH v2] Input: byd - synchronize timer deletion before freeing private data

[Linmao Li]

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: 2d5f5611dd0d ("Input: byd - enable absolute mode")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Linmao Li <lilinmao@xxxxxxxxxx>
---
v2:
- use timer_shutdown_sync() instead of timer_delete_sync() so the
  timer cannot be re-armed by byd_process_byte() while disconnect is
  in progress (Sashiko review, Dmitry)

 drivers/input/mouse/byd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/mouse/byd.c b/drivers/input/mouse/byd.c
index f5770a3af2f1..5fc3c629590a 100644
--- a/drivers/input/mouse/byd.c
+++ b/drivers/input/mouse/byd.c
@@ -423,7 +423,7 @@ static void byd_disconnect(struct psmouse *psmouse)
 	struct byd_data *priv = psmouse->private;
 
 	if (priv) {
-		timer_delete(&priv->timer);
+		timer_shutdown_sync(&priv->timer);
 		kfree(psmouse->private);
 		psmouse->private = NULL;
 	}
-- 
2.25.1