Re: [PATCH] drm/virtio: add driver_priv validation in virtio_gpu_create_context

[Dmitry Osipenko]

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@xxxxxxxxx>
> ---
>  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