linux-kernel - Re: [PATCH] drm/virtio: add driver_priv validation in virtio_gpu_create

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Message-ID: <6ca1e5de-2188-466f-a05c-ba190702d7a5@collabora.com>
Date: Thu, 11 Apr 2024 15:31:24 +0300
From: Dmitry Osipenko <dmitry.osipenko@...labora.com>
To: Maxim Korotkov <korotkov.maxim.s@...il.com>,
 David Airlie <airlied@...hat.com>
Cc: Gerd Hoffmann <kraxel@...hat.com>,
 Gurchetan Singh <gurchetansingh@...omium.org>, Chia-I Wu
 <olvaffe@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Daniel Vetter <daniel@...ll.ch>, Ivan Kapranov <i.kapranov@...uritycode.ru>,
 lvc-project@...uxtesting.org, dri-devel@...ts.freedesktop.org,
 virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/virtio: add driver_priv validation in
 virtio_gpu_create_context

On 3/28/24 16:43, Maxim Korotkov wrote:
> The pointer file->driver_priv was dereferenced without checking
> against NULL, but in the "virtio_gpu_transfer_to_host_ioctl" function
> it was checked against NULL after calling virtio_gpu_create_context
> function.
> 
> Found by Security Code and Linux Verification Center(linuxtesting.org)
> Fixes: 72b48ae800da ("drm/virtio: enqueue virtio_gpu_create_context after the first 3D ioctl")
> Signed-off-by: Maxim Korotkov <korotkov.maxim.s@...il.com>
> ---
>  drivers/gpu/drm/virtio/virtgpu_ioctl.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> index e4f76f315550..98fe9ad4ed15 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> @@ -64,6 +64,9 @@ void virtio_gpu_create_context(struct drm_device *dev, struct drm_file *file)
>  	struct virtio_gpu_device *vgdev = dev->dev_private;
>  	struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
>  
> +	if (!vfpriv)
> +		return;
> +
>  	mutex_lock(&vfpriv->context_lock);
>  	if (vfpriv->context_created)
>  		goto out_unlock;

NULL check in virtio_gpu_transfer_to_host_ioctl() is bogus, vfpriv can't
be NULL there.

-- 
Best regards,
Dmitry