[PATCH 1/2] media: i2c: ov7740: Fix use-after-destroy in remove()

[Biren Pandya <birenpandya@gmail.com>]

The ov7740_remove() function had a severe teardown order bug where it
destroyed the driver's mutex before freeing the V4L2 control handler
which relies on that mutex, leading to a use-after-destroy kernel panic.
Furthermore, the driver explicitly called v4l2_ctrl_handler_free() and
mutex_destroy() sequentially, but then called ov7740_free_controls()
which invokes both of them a second time, resulting in a double-free.

This patch fixes the issue by unregistering the subdevice first, and
relying exclusively on ov7740_free_controls() to safely tear down the
mutex and control handler in the correct order.

Fixes: 39c5c4471b8d ("media: i2c: Add the ov7740 image sensor driver")
Signed-off-by: Biren Pandya <birenpandya@gmail.com>
---
 drivers/media/i2c/ov7740.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/media/i2c/ov7740.c b/drivers/media/i2c/ov7740.c
index 632fb80469be..62c124a1353a 100644
--- a/drivers/media/i2c/ov7740.c
+++ b/drivers/media/i2c/ov7740.c
@@ -1116,10 +1116,8 @@ static void ov7740_remove(struct i2c_client *client)
 	struct v4l2_subdev *sd = i2c_get_clientdata(client);
 	struct ov7740 *ov7740 = container_of(sd, struct ov7740, subdev);
 
-	mutex_destroy(&ov7740->mutex);
-	v4l2_ctrl_handler_free(ov7740->subdev.ctrl_handler);
-	media_entity_cleanup(&ov7740->subdev.entity);
 	v4l2_async_unregister_subdev(sd);
+	media_entity_cleanup(&ov7740->subdev.entity);
 	ov7740_free_controls(ov7740);
 
 	pm_runtime_get_sync(&client->dev);
-- 
2.50.1 (Apple Git-155)