[PATCH] drm/virtio: Fix NULL dereference error in virtio_gpu_poll

[Gerd Hoffmann]

On Thu, Nov 04, 2021 at 02:42:49PM -0700, Vivek Kasireddy wrote:
> When virgl is not enabled, vfpriv pointer would not be allocated.
> Therefore, check for a valid value before dereferencing.
> 
> Reported-by: Christian Zigotzky <chzigotzky at xenosoft.de>
> Cc: Gurchetan Singh <gurchetansingh at chromium.org>
> Cc: Gerd Hoffmann <kraxel at redhat.com>
> Signed-off-by: Vivek Kasireddy <vivek.kasireddy at intel.com>
> ---
>  drivers/gpu/drm/virtio/virtgpu_drv.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
> index 749db18dcfa2..d86e1ad4a972 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
> @@ -163,10 +163,11 @@ static __poll_t virtio_gpu_poll(struct file *filp,
>  	struct drm_file *drm_file = filp->private_data;
>  	struct virtio_gpu_fpriv *vfpriv = drm_file->driver_priv;
>  	struct drm_device *dev = drm_file->minor->dev;
> +	struct virtio_gpu_device *vgdev = dev->dev_private;
>  	struct drm_pending_event *e = NULL;
>  	__poll_t mask = 0;
>  
> -	if (!vfpriv->ring_idx_mask)
> +	if (!vgdev->has_virgl_3d || !vfpriv || !vfpriv->ring_idx_mask)
>  		return drm_poll(filp, wait);
>  
>  	poll_wait(filp, &drm_file->event_wait, wait);

Pushed to drm-misc-next-fixes.

thanks,
  Gerd