{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98156","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-25T10:25:14.320Z","datePublished":"2026-09-25T10:36:26.409Z","dateUpdated":"2026-09-25T14:42:14.960Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-25T14:42:14.960Z"},"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->vdev);\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's 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't need this fix because it is identity-mapped,\nonly PV dom0s are affected."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"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's security authority.\nC:H - virtio_gpu_cmd_transfer_to_host_2d/3d make the host copy unrelated machine pages (other domains' 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' memory, crashing them. The unsynced swiotlb path (missing dma_sync_sgtable_for_device) also corrupts display data."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/virtio/virtgpu_drv.h","drivers/gpu/drm/virtio/virtgpu_object.c","drivers/gpu/drm/virtio/virtgpu_vq.c"],"versions":[{"version":"a3b815f09bb846255c458c181b8a5b1cc66891b4","lessThan":"93c557e947ef0040004b1ac6a1c1265d79a957e1","status":"affected","versionType":"git"},{"version":"a3b815f09bb846255c458c181b8a5b1cc66891b4","lessThan":"455184dbe9652d01470d3c5cf5edd09a7a673a99","status":"affected","versionType":"git"},{"version":"a3b815f09bb846255c458c181b8a5b1cc66891b4","lessThan":"6a736d2f9d0c6e6217fe7532bc4c50ceca71db78","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/virtio/virtgpu_drv.h","drivers/gpu/drm/virtio/virtgpu_object.c","drivers/gpu/drm/virtio/virtgpu_vq.c"],"versions":[{"version":"4.20","status":"affected"},{"version":"0","lessThan":"4.20","status":"unaffected","versionType":"semver"},{"version":"6.18.53","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.7","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20","versionEndExcluding":"7.3-rc2"}]}]}],"references":[{"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"}}}}