[PATCH] media: meson: ge2d: avoid double free on video register failure

[Guangshuo Li <lgs201920130244@gmail.com>]

ge2d_probe() allocates a video_device with video_device_alloc() and
releases it from the rel_vdev error path if video_register_device()
fails.

This can double free the video_device when __video_register_device()
reaches device_register() and that call fails:

  video_register_device()
    -> __video_register_device()
       -> device_register() fails
          -> put_device(&vdev->dev)
             -> v4l2_device_release()
                -> vdev->release(vdev)
                   -> video_device_release(vdev)

  ge2d_probe()
    -> rel_vdev
       -> video_device_release(ge2d->vfd)

Use video_device_release_empty() while registering the device so that
registration failure paths do not free ge2d->vfd through vdev->release().
ge2d_probe() then releases ge2d->vfd exactly once from rel_vdev. Restore
video_device_release() after successful registration so the registered
device keeps its normal lifetime handling.

This issue was found by a static analysis tool I am developing.

Fixes: 59a635327ca7 ("media: meson: Add M2M driver for the Amlogic GE2D Accelerator Unit")
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
 drivers/media/platform/amlogic/meson-ge2d/ge2d.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/platform/amlogic/meson-ge2d/ge2d.c b/drivers/media/platform/amlogic/meson-ge2d/ge2d.c
index c5dc03905ce0..b367169e6ad8 100644
--- a/drivers/media/platform/amlogic/meson-ge2d/ge2d.c
+++ b/drivers/media/platform/amlogic/meson-ge2d/ge2d.c
@@ -983,6 +983,7 @@ static int ge2d_probe(struct platform_device *pdev)
 	}
 
 	*vfd = ge2d_videodev;
+	vfd->release = video_device_release_empty;
 	vfd->lock = &ge2d->mutex;
 	vfd->v4l2_dev = &ge2d->v4l2_dev;
 
@@ -1005,6 +1006,7 @@ static int ge2d_probe(struct platform_device *pdev)
 
 	v4l2_info(&ge2d->v4l2_dev, "Registered %s as /dev/%s\n",
 		  vfd->name, video_device_node_name(vfd));
+	vfd->release = video_device_release;
 
 	return 0;
 
-- 
2.43.0