---
id: CVE-2026-98156
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  drm/virtio: use the DMA API for resource backing on Xen

  On a Xen PV domain page addresses bear no relation to the real machine
  addresses the host would have to use to …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  drm/virtio: use the DMA API for resource backing on Xen

  On a Xen PV domain page addresses bear no relation to the real machine
  addresses the host would have to use to …
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= a3b815f09bb846255c458c181b8a5b1cc66891b4 <
    93c557e947ef0040004b1ac6a1c1265d79a957e1
  - >-
    Linux >= a3b815f09bb846255c458c181b8a5b1cc66891b4 <
    455184dbe9652d01470d3c5cf5edd09a7a673a99
  - >-
    Linux >= a3b815f09bb846255c458c181b8a5b1cc66891b4 <
    6a736d2f9d0c6e6217fe7532bc4c50ceca71db78
  - Linux 4.20
published: '2026-09-25'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T15:18:07.240'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-98156'
references:
  - url: 'https://git.kernel.org/stable/c/455184dbe9652d01470d3c5cf5edd09a7a673a99'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6a736d2f9d0c6e6217fe7532bc4c50ceca71db78'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/93c557e947ef0040004b1ac6a1c1265d79a957e1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-25T11:06:38.803Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

drm/virtio: use the DMA API for resource backing on Xen

On a Xen PV domain page addresses bear no relation to the real machine
addresses the host would have to use to reach it.
virtio_ring.c handles this correctly, vring_use_map_api() returns true
for any xen_domain() regardless of VIRTIO_F_ACCESS_PLATFORM.

virtio-gpu makes the same decision independently, but its copy
looks only at the feature bit:

	bool use_dma_api = !virtio_has_dma_quirk(vgdev->vdev);

QEMU does not set iommu_platform on virtio-vga by default, so
VIRTIO_F_ACCESS_PLATFORM is not negotiated, use_dma_api is false, and
virtio_gpu_object_shmem_init() describes the framebuffer's backing pages
to the host with sg_phys().  Those are guest-physical addresses. In a PV
domain they resolve, on the host side, to pages belonging to some other
domain, so the host scans out unrelated memory.

Move the decision into virtio_gpu_use_dma_api() and give it the
xen_domain() check, like vring_use_map_api() has. This
additionally enables the dma_sync_sgtable_for_device() calls in
virtgpu_vq.c, which are required for correctness whenever swiotlb
is in play.

Reproduced with a Xen 4.21 PV dom0 nested inside QEMU 8.2 with
virtio-vga, on both a distro 6.8 kernel and 6.18 LTS. A PVH dom0
works fine and doesn't need this fix because it is identity-mapped,
only PV dom0s are affected.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.