media: vidtv: move kfree(dvb) to vidtv_bridge_dev_release()

Adding kfree(dvb) to vidtv_bridge_remove() will remove the memory
too soon: if an application still has an open filehandle to the device
when the driver is unloaded, then when that filehandle is closed, a
use-after-free access takes place to the freed memory.

Move the kfree(dvb) to vidtv_bridge_dev_release() instead.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: 76e21bb8 ("media: vidtv: Fix memory leak in remove")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/test-drivers/vidtv/vidtv_bridge.c

@@ -557,7 +557,6 @@ static int vidtv_bridge_remove(struct platform_device *pdev)
 	dvb_dmxdev_release(&dvb->dmx_dev);
 	dvb_dmx_release(&dvb->demux);
 	dvb_unregister_adapter(&dvb->adapter);
-	kfree(dvb);
 	dev_info(&pdev->dev, "Successfully removed vidtv\n");
 
 	return 0;
@@ -565,6 +564,10 @@ static int vidtv_bridge_remove(struct platform_device *pdev)
 
 static void vidtv_bridge_dev_release(struct device *dev)
 {
+	struct vidtv_dvb *dvb;
+
+	dvb = dev_get_drvdata(dev);
+	kfree(dvb);
 }
 
 static struct platform_device vidtv_bridge_dev = {