On Sat, Oct 13, 2018 at 11:02 AM Akinobu Mita <akinobu.mita@xxxxxxxxx> wrote:
>
> The video device release() callback for video-i2c driver frees the whole
> struct video_i2c_data. If there is no user left for the video device
> when video_unregister_device() is called, the release callback is executed.
>
> However, in video_i2c_remove() some fields (v4l2_dev, lock, and queue_lock)
> in struct video_i2c_data are still accessed after video_unregister_device()
> is called.
>
> This fixes the use after free by moving the code from video_i2c_remove()
> to the release() callback.
>
> Fixes: 5cebaac60974 ("media: video-i2c: add video-i2c driver")
> Cc: Matt Ranostay <matt.ranostay@xxxxxxxxxxxx>
Reviewed-by: Matt Ranostay <matt.ranostay@xxxxxxxxxxxx>
> Cc: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> Cc: Hans Verkuil <hansverk@xxxxxxxxx>
> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> ---
> * v3
> - Move the code causing use-after-free from video_i2c_remove() to the
> video device release() callback.
> - Remove Acked-by line as there are enough changes from previous version
>
> drivers/media/i2c/video-i2c.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/i2c/video-i2c.c b/drivers/media/i2c/video-i2c.c
> index 06d29d8..f27d294 100644
> --- a/drivers/media/i2c/video-i2c.c
> +++ b/drivers/media/i2c/video-i2c.c
> @@ -510,7 +510,12 @@ static const struct v4l2_ioctl_ops video_i2c_ioctl_ops = {
>
> static void video_i2c_release(struct video_device *vdev)
> {
> - kfree(video_get_drvdata(vdev));
> + struct video_i2c_data *data = video_get_drvdata(vdev);
> +
> + v4l2_device_unregister(&data->v4l2_dev);
> + mutex_destroy(&data->lock);
> + mutex_destroy(&data->queue_lock);
> + kfree(data);
> }
>
> static int video_i2c_probe(struct i2c_client *client,
> @@ -608,10 +613,6 @@ static int video_i2c_remove(struct i2c_client *client)
> struct video_i2c_data *data = i2c_get_clientdata(client);
>
> video_unregister_device(&data->vdev);
> - v4l2_device_unregister(&data->v4l2_dev);
> -
> - mutex_destroy(&data->lock);
> - mutex_destroy(&data->queue_lock);
>
> return 0;
> }
> --
> 2.7.4
>
