[PATCH] media: mediatek: jpeg: avoid double free on video register failure

[Guangshuo Li]

mtk_jpeg_probe() allocates a video_device with video_device_alloc() and
releases it from the err_vfd_jpeg_register 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)

  mtk_jpeg_probe()
    -> err_vfd_jpeg_register
       -> video_device_release(jpeg->vdev)

Use video_device_release_empty() while registering the device so that
registration failure paths do not free jpeg->vdev through vdev->release().
mtk_jpeg_probe() then releases jpeg->vdev exactly once from
err_vfd_jpeg_register. 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: 2ac8015f156b ("media: platform: Rename existing functions/defines/variables")
Signed-off-by: Guangshuo Li <lgs201920130244 at gmail.com>
---
 drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
index c01124a349f6..9888ac8dd6e4 100644
--- a/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
+++ b/drivers/media/platform/mediatek/jpeg/mtk_jpeg_core.c
@@ -1362,7 +1362,7 @@ static int mtk_jpeg_probe(struct platform_device *pdev)
 	jpeg->vdev->fops = &mtk_jpeg_fops;
 	jpeg->vdev->ioctl_ops = jpeg->variant->ioctl_ops;
 	jpeg->vdev->minor = -1;
-	jpeg->vdev->release = video_device_release;
+	jpeg->vdev->release = video_device_release_empty;
 	jpeg->vdev->lock = &jpeg->lock;
 	jpeg->vdev->v4l2_dev = &jpeg->v4l2_dev;
 	jpeg->vdev->vfl_dir = VFL_DIR_M2M;
@@ -1374,6 +1374,7 @@ static int mtk_jpeg_probe(struct platform_device *pdev)
 		v4l2_err(&jpeg->v4l2_dev, "Failed to register video device\n");
 		goto err_vfd_jpeg_register;
 	}
+	jpeg->vdev->release = video_device_release;
 
 	video_set_drvdata(jpeg->vdev, jpeg);
 	v4l2_info(&jpeg->v4l2_dev,
-- 
2.43.0