In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/virtio: use the DMA API for resource backing on Xen<\/p>\n
On 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.<\/p>\n
virtio-gpu makes the same decision independently, but its copy
\nlooks only at the feature bit:<\/p>\n
\tbool use_dma_api = !virtio_has_dma_quirk(vgdev->vdev);<\/p>\n
QEMU 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.<\/p>\n
Move 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.<\/p>\n
Reproduced 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.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/virtio: use the DMA API for resource backing on Xen<\/p>\n
On a Xen PV domain page addresses bear no relation to the real machine
\nadd<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-29310","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/29310","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=29310"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=29310"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=29310"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}