CVE-2026-98156

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

Published Sep 25, 2026 CVSS 3.1 · 7.8 High EPSS < 1% KEV · Not listed
Description
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

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4904-1 linux-6.12 security update
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9091-1 Linux kernel (NVIDIA Tegra) vulnerabilities
History
Type Values Removed Values Added
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:o:linux:linux_kernel:7.3:rc1:*:*:*:*:*:*
Type Values Removed Values Added
Weaknesses CWE-200
CWE-279
Type Values Removed Values Added
Weaknesses CWE-200
CWE-279
Type Values Removed Values Added
Weaknesses CWE-200
CWE-284
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-200
CWE-284
Type Values Removed Values Added
Description 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.
Title drm/virtio: use the DMA API for resource backing on Xen
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 21, 2026, 12:54 PM
Reserved
Sep 25, 2026, 10:25 AM
Status
Modified
Published
Sep 25, 2026, 11:17 AM
Modified
Oct 21, 2026, 1:21 PM
Severity
Moderate
Public date
Sep 25, 2026, 12:00 AM