KVM: Reject wrapped offset in kvm_reset_dirty_gfn()

{
  "id": "aef4128ee7d73ebdcf2fd730f70da26c19d00bb50ed941d424441339da51e5f3",
  "url": "https://osv.dev/vulnerability/CVE-2026-52969",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "KVM: Reject wrapped offset in kvm_reset_dirty_gfn()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: KVM: Reject wrapped offset in kvm_reset_dirty_gfn() kvm_reset_dirty_gfn() guards the gfn range with if (!memslot || (offset + __fls(mask)) >= memslot->npages) return; but offset is u64 and the addition is unchecked. The check can be silently bypassed by a u64 wrap. The dirty ring backing those entries is MAP_SHARED at KVM_DIRTY_LOG_PAGE_OFFSET of the vcpu fd, so the VMM can rewrite the slot and offset fields of any entry between when the kernel pushes them and when KVM_RESET_DIRTY_RINGS consumes them. On reset, kvm_dirty_ring_reset() re-reads the values via READ_ONCE() and feeds them straight back into this check; only the flags handshake is treated as the handover, the slot/offset payload is taken on trust. Crafting two entries entry[i].offset = 0xffffffffffffffc1 entry[i+1].offset = 0 makes the coalescing loop in kvm_dirty_ring_reset() compute delta = (s64)(0 - 0xffffffffffffffc1) = 63 which falls in [0, BITS_PER_LONG), so it folds entry[i+1] into the existing mask by setting bit 63. The trailing kvm_reset_dirty_gfn() call then sees offset = 0xffffffffffffffc1 and __fls(mask) = 63; the sum is 0 in u64 and the bounds check passes. That offset propagates into kvm_arch_mmu_enable_log_dirty_pt_masked() unchanged. On the legacy MMU path -- kvm_memslots_have_rmaps() == true, i.e. shadow paging, any VM that has allocated shadow roots, or a write-tracked slot -- it reaches gfn_to_rmap(), which indexes slot->arch.rm",
    "evidence": "osv:CVE-2026-52969",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.15.209",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.175",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.141",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.91",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.33",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.0.10",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-52969",
      "aliases": [
        "CVE-2026-52969"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fb04a1eddb1a65b6588a021bdc132270d5ae48bb"
                },
                {
                  "fixed": "74f1a22f7a80f03d28ad8551a2d25d563433addf"
                },
                {
                  "fixed": "0eb281eb95b2d4eea4db1da5fe91023aecc97095"
                },
                {
                  "fixed": "01b71b930f15728aa8599478a7ce90c19dcd9fc2"
                },
                {
                  "fixed": "b315b033a877b1ee6d827810b5d7bb4392ffcf8d"
                },
                {
                  "fixed": "0d419c23bb11b5c9664de777c47c1f04a235882d"
                },
                {
                  "fixed": "ecf9b3ea7847fe14f34b8c41f00de1eb95c747da"
                },
                {
                  "fixed": "577a8d3bae0531f0e5ccfac919cd8192f920a804"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-52969.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.209"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.175"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.141"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.91"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.33"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.0.10"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-52969.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:52.963598758Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/01b71b930f15728aa8599478a7ce90c19dcd9fc2",
        "https://git.kernel.org/stable/c/0d419c23bb11b5c9664de777c47c1f04a235882d",
        "https://git.kernel.org/stable/c/0eb281eb95b2d4eea4db1da5fe91023aecc97095",
        "https://git.kernel.org/stable/c/577a8d3bae0531f0e5ccfac919cd8192f920a804",
        "https://git.kernel.org/stable/c/74f1a22f7a80f03d28ad8551a2d25d563433addf",
        "https://git.kernel.org/stable/c/b315b033a877b1ee6d827810b5d7bb4392ffcf8d",
        "https://git.kernel.org/stable/c/ecf9b3ea7847fe14f34b8c41f00de1eb95c747da",
        "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52969.json",
        "https://access.redhat.com/security/cve/CVE-2026-52969",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52969.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-52969",
        "https://bugzilla.redhat.com/show_bug.cgi?id=2492434",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52969.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-52969",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 521533,
  "published_at": "2026-06-24T16:28:48.085+00:00"
}