[PATCH 6/7] v4l2-device: v4l2_device_release_subdev_node can't reference sd

[Hans Verkuil <hverkuil-cisco@xs4all.nl>]

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.

Signed-off-by: Hans Verkuil <hverkuil-cisco@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);
 }
-- 
2.20.1