saa7164_encoder_register() allocates a video_device and releases it from
the fail_reg 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)

  saa7164_encoder_register()
    -> fail_reg
       -> video_device_release(port->v4l_device)

Use video_device_release_empty() while registering the device so that
registration failure paths do not free port->v4l_device through
vdev->release(). saa7164_encoder_register() then releases
port->v4l_device exactly once from fail_reg. 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: c759b2970c56 ("media: media/saa7164: fix saa7164_encoder_register() memory leak bugs")
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
 drivers/media/pci/saa7164/saa7164-encoder.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/pci/saa7164/saa7164-encoder.c b/drivers/media/pci/saa7164/saa7164-encoder.c
index 64380741b984..e23b44d1fc3b 100644
--- a/drivers/media/pci/saa7164/saa7164-encoder.c
+++ b/drivers/media/pci/saa7164/saa7164-encoder.c
@@ -1081,6 +1081,7 @@ int saa7164_encoder_register(struct saa7164_port *port)
 	}
 
 	port->v4l_device->ctrl_handler = hdl;
+	port->v4l_device->release = video_device_release_empty;
 	v4l2_ctrl_handler_setup(hdl);
 	video_set_drvdata(port->v4l_device, port);
 	result = video_register_device(port->v4l_device,
@@ -1090,6 +1091,7 @@ int saa7164_encoder_register(struct saa7164_port *port)
 			dev->name);
 		goto fail_reg;
 	}
+	port->v4l_device->release = video_device_release;
 
 	printk(KERN_INFO "%s: registered device video%d [mpeg]\n",
 		dev->name, port->v4l_device->num);
-- 
2.43.0