Re: [PATCH AUTOSEL 4.4 08/31] drm/virtio: Fixes a potential NULL pointer dereference on probe failure

[Sasha Levin]

On Mon, Jul 12, 2021 at 11:59:37PM +0200, Pavel Machek wrote:
> Hi!
>
> > From: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
> >
> > [ Upstream commit 17f46f488a5d82c5568e6e786cd760bba1c2ee09 ]
> >
> > The dev->dev_private might not be allocated if virtio_gpu_pci_quirk()
> > or virtio_gpu_init() failed. In this case, we should avoid the cleanup
> > in virtio_gpu_release().
>
> The check is in wrong place at least in 4.4:
>
> > +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c
> > @@ -257,6 +257,9 @@ int virtio_gpu_driver_unload(struct drm_device *dev)
> >  	flush_work(&vgdev->config_changed_work);
> >  	vgdev->vdev->config->del_vqs(vgdev->vdev);
> >
> > +	if (!vgdev)
> > +		return;
> > +
>
> Pointer is dereferenced before being tested.

Heh, yes, thanks for catching that. I'll drop it for now and rework it
next week.

--
Thanks,
Sasha