Hi Hans,
Thank you for the patch.
On Thu, Feb 21, 2019 at 03:21:47PM +0100, Hans Verkuil wrote:
> When the v4l-subdev device node is released it calls the
> v4l2_device_release_subdev_node() function which sets sd->devnode
> to NULL.
>
> However, the v4l2_subdev struct may already be released causing this
> to write in freed memory.
>
> Instead just use the regular video_device_release release function
> (just calls kfree) and set sd->devnode to NULL right after the
> video_unregister_device() call.
This seems a bit of a workaround. The devnode can access the subdev in
multiple ways, it should really keep a reference to the subdev to ensure
it doesn't get freed early.
> Signed-off-by: Hans Verkuil <hverkuil-ci...@xs4all.nl>
> ---
> drivers/media/v4l2-core/v4l2-device.c | 10 ++--------
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-device.c
> b/drivers/media/v4l2-core/v4l2-device.c
> index e0ddb9a52bd1..57a7b220fa4d 100644
> --- a/drivers/media/v4l2-core/v4l2-device.c
> +++ b/drivers/media/v4l2-core/v4l2-device.c
> @@ -216,13 +216,6 @@ int v4l2_device_register_subdev(struct v4l2_device
> *v4l2_dev,
> }
> EXPORT_SYMBOL_GPL(v4l2_device_register_subdev);
>
> -static void v4l2_device_release_subdev_node(struct video_device *vdev)
> -{
> - struct v4l2_subdev *sd = video_get_drvdata(vdev);
> - sd->devnode = NULL;
> - kfree(vdev);
> -}
> -
> int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
> {
> struct video_device *vdev;
> @@ -250,7 +243,7 @@ int v4l2_device_register_subdev_nodes(struct v4l2_device
> *v4l2_dev)
> vdev->dev_parent = sd->dev;
> vdev->v4l2_dev = v4l2_dev;
> vdev->fops = &v4l2_subdev_fops;
> - vdev->release = v4l2_device_release_subdev_node;
> + vdev->release = video_device_release;
> vdev->ctrl_handler = sd->ctrl_handler;
> err = __video_register_device(vdev, VFL_TYPE_SUBDEV, -1, 1,
> sd->owner);
> @@ -319,6 +312,7 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev *sd)
> }
> #endif
> video_unregister_device(sd->devnode);
> + sd->devnode = NULL;
> if (!sd->owner_v4l2_dev)
> module_put(sd->owner);
> }
--
Regards,
Laurent Pinchart
