CVE-2026-98156 (GCVE-0-2026-98156)
Vulnerability from cvelistv5
Published
2026-09-25 10:36
Modified
2026-10-21 12:54
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
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 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.
References
Impacted products
Vendor Product Version
Linux Linux Version: a3b815f09bb846255c458c181b8a5b1cc66891b4
Version: a3b815f09bb846255c458c181b8a5b1cc66891b4
Version: a3b815f09bb846255c458c181b8a5b1cc66891b4
Version: a3b815f09bb846255c458c181b8a5b1cc66891b4
Version: a3b815f09bb846255c458c181b8a5b1cc66891b4
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/gpu/drm/virtio/virtgpu_drv.h",
            "drivers/gpu/drm/virtio/virtgpu_object.c",
            "drivers/gpu/drm/virtio/virtgpu_vq.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "32e999ccf5f6453b3b4df8264ff1b03c6720292f",
              "status": "affected",
              "version": "a3b815f09bb846255c458c181b8a5b1cc66891b4",
              "versionType": "git"
            },
            {
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              "status": "affected",
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              "versionType": "git"
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            {
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              "status": "affected",
              "version": "a3b815f09bb846255c458c181b8a5b1cc66891b4",
              "versionType": "git"
            },
            {
              "lessThan": "455184dbe9652d01470d3c5cf5edd09a7a673a99",
              "status": "affected",
              "version": "a3b815f09bb846255c458c181b8a5b1cc66891b4",
              "versionType": "git"
            },
            {
              "lessThan": "6a736d2f9d0c6e6217fe7532bc4c50ceca71db78",
              "status": "affected",
              "version": "a3b815f09bb846255c458c181b8a5b1cc66891b4",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/gpu/drm/virtio/virtgpu_drv.h",
            "drivers/gpu/drm/virtio/virtgpu_object.c",
            "drivers/gpu/drm/virtio/virtgpu_vq.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.20"
            },
            {
              "lessThan": "4.20",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.160",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.114",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.160",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.114",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.53",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.7",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "4.20",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/virtio: use the DMA API for resource backing on Xen\n\nOn a Xen PV domain page addresses bear no relation to the real machine\naddresses the host would have to use to reach it.\nvirtio_ring.c handles this correctly, vring_use_map_api() returns true\nfor any xen_domain() regardless of VIRTIO_F_ACCESS_PLATFORM.\n\nvirtio-gpu makes the same decision independently, but its copy\nlooks only at the feature bit:\n\n\tbool use_dma_api = !virtio_has_dma_quirk(vgdev-\u003evdev);\n\nQEMU does not set iommu_platform on virtio-vga by default, so\nVIRTIO_F_ACCESS_PLATFORM is not negotiated, use_dma_api is false, and\nvirtio_gpu_object_shmem_init() describes the framebuffer\u0027s backing pages\nto the host with sg_phys().  Those are guest-physical addresses. In a PV\ndomain they resolve, on the host side, to pages belonging to some other\ndomain, so the host scans out unrelated memory.\n\nMove the decision into virtio_gpu_use_dma_api() and give it the\nxen_domain() check, like vring_use_map_api() has. This\nadditionally enables the dma_sync_sgtable_for_device() calls in\nvirtgpu_vq.c, which are required for correctness whenever swiotlb\nis in play.\n\nReproduced with a Xen 4.21 PV dom0 nested inside QEMU 8.2 with\nvirtio-vga, on both a distro 6.8 kernel and 6.18 LTS. A PVH dom0\nworks fine and doesn\u0027t need this fix because it is identity-mapped,\nonly PV dom0s are affected."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The attacker is a local process in the Xen PV dom0. It opens the virtio-gpu render node and calls VIRTGPU_RESOURCE_CREATE, which runs virtio_gpu_object_shmem_init(), and then VIRTGPU_TRANSFER_TO_HOST or TRANSFER_FROM_HOST. No remote peer supplies the bad sg_phys() addresses; the guest driver builds them itself.\nAC:H - The bug only exists on a Xen PV dom0 nested inside QEMU with virtio-vga and without iommu_platform, so VIRTIO_F_ACCESS_PLATFORM is not negotiated. This is a rare deployment the attacker cannot create. The attacker also cannot choose which foreign machine frames the pseudo-physical pfns resolve to.\nPR:L - VIRTGPU_RESOURCE_CREATE, TRANSFER_TO_HOST and TRANSFER_FROM_HOST are all marked DRM_RENDER_ALLOW. Any user with access to /dev/dri/renderD* (render group or a logind seat ACL) can reach them without root.\nUI:N - The attacker creates the resource and issues the transfer ioctls entirely on their own. No other user has to act.\nS:C - virtio_gpu_object_shmem_init() hands the host guest-pseudo-physical addresses, which the host resolves to machine frames owned by other Xen domains or by Xen itself. So a flaw in the dom0 driver affects memory outside that domain\u0027s security authority.\nC:H - virtio_gpu_cmd_transfer_to_host_2d/3d make the host copy unrelated machine pages (other domains\u0027 memory) into a host resource, which is then scanned out. With virgl, the attacker could plausibly copy that resource into memory they can read back.\nI:H - With virgl, VIRTGPU_TRANSFER_FROM_HOST makes the host write resource data to the wrong backing addresses. Those addresses are machine frames belonging to other domains or the hypervisor, so this is an uncontrolled cross-domain memory write.\nA:H - Host writes into foreign machine frames through the bad backing entries can corrupt Xen or other domains\u0027 memory, crashing them. The unsynced swiotlb path (missing dma_sync_sgtable_for_device) also corrupts display data."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:54:43.922Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/32e999ccf5f6453b3b4df8264ff1b03c6720292f"
        },
        {
          "url": "https://git.kernel.org/stable/c/3f130cc6826fabf50e01fe8e4ff3ed1fcae50d36"
        },
        {
          "url": "https://git.kernel.org/stable/c/93c557e947ef0040004b1ac6a1c1265d79a957e1"
        },
        {
          "url": "https://git.kernel.org/stable/c/455184dbe9652d01470d3c5cf5edd09a7a673a99"
        },
        {
          "url": "https://git.kernel.org/stable/c/6a736d2f9d0c6e6217fe7532bc4c50ceca71db78"
        }
      ],
      "title": "drm/virtio: use the DMA API for resource backing on Xen",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98156",
    "datePublished": "2026-09-25T10:36:26.409Z",
    "dateReserved": "2026-09-25T10:25:14.320Z",
    "dateUpdated": "2026-10-21T12:54:43.922Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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