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

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Date:   Mon, 12 Jul 2021 23:59:37 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Xie Yongji <xieyongji@...edance.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        dri-devel@...ts.freedesktop.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH AUTOSEL 4.4 08/31] drm/virtio: Fixes a potential NULL
 pointer dereference on probe failure

Hi!

> From: Xie Yongji <xieyongji@...edance.com>
> 
> [ 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.

Best regards,
								Pavel
--
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany


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