Re: [PATCH v2] drm/virtio: do not enforce blob_alignment in cross-domain contexts

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] drm/virtio: blob size alignment check is bypassed for 2D devices
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commit e9be6e8827fcf796e95413bb22d054eb21acf9b4
Author: Val Packett <val@invisiblethingslab.com>

drm/virtio: do not enforce blob_alignment in cross-domain contexts

This commit stops enforcing blob_alignment requirements in cross-domain
contexts. Resources created under these contexts are arbitrary shared system
memory files rather than GPU rendering contexts, so alignment is no longer
strictly enforced.

Link: https://lore.kernel.org/all/20261006004044.2242154-1-val@invisiblethingslab.com/

> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> index 81e70a12b3569..c28534593b2f4 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
> @@ -539,7 +539,9 @@ static int verify_blob(struct virtio_gpu_device *vgdev,
>  	params->blob_flags = rc_blob->blob_flags;
>  	params->blob_hints = rc_blob->blob_hints;
>  
> -	if (vgdev->has_blob_alignment &&
> +	if (vgdev->has_blob_alignment && vgdev->has_virgl_3d &&
> +	    (vfpriv->context_init & VIRTIO_GPU_CONTEXT_INIT_CAPSET_ID_MASK) !=
> +	    VIRTIO_GPU_CAPSET_CROSS_DOMAIN &&
>  	    !IS_ALIGNED(params->size, vgdev->blob_alignment))
>  		return -EINVAL;

[Severity: Medium]
Does adding the vgdev->has_virgl_3d check here completely bypass the size
alignment validation for 2D devices?

If has_virgl_3d is false, the condition short-circuits and skips the
IS_ALIGNED() check entirely. This seems to allow userspace to request
unaligned blob sizes on non-3D devices, which could potentially cause
host-side errors or command rejection.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261006154913.2689067-2-val@invisiblethingslab.com?part=1