[PATCH] media: rockchip: rga: avoid double free on video register failure

[Guangshuo Li]

rga_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)

  rga_probe()
    -> rel_vdev
       -> video_device_release(vfd)

Use video_device_release_empty() while registering the device so that
registration failure paths do not free vfd through vdev->release().
rga_probe() then releases 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: f7e7b48e6d79 ("[media] rockchip/rga: v4l2 m2m support")
Signed-off-by: Guangshuo Li <lgs201920130244 at gmail.com>
---
 drivers/media/platform/rockchip/rga/rga.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/platform/rockchip/rga/rga.c b/drivers/media/platform/rockchip/rga/rga.c
index fea63b94c5f3..90ae01de3216 100644
--- a/drivers/media/platform/rockchip/rga/rga.c
+++ b/drivers/media/platform/rockchip/rga/rga.c
@@ -851,6 +851,7 @@ static int rga_probe(struct platform_device *pdev)
 		goto unreg_v4l2_dev;
 	}
 	*vfd = rga_videodev;
+	vfd->release = video_device_release_empty;
 	vfd->lock = &rga->mutex;
 	vfd->v4l2_dev = &rga->v4l2_dev;
 
@@ -895,6 +896,8 @@ static int rga_probe(struct platform_device *pdev)
 		goto free_dma;
 	}
 
+	vfd->release = video_device_release;
+
 	v4l2_info(&rga->v4l2_dev, "Registered %s as /dev/%s\n",
 		  vfd->name, video_device_node_name(vfd));
 
-- 
2.43.0