mm/util: don't read __page_2 for order-1 folios in snapshot_page()

{
  "id": "74902d26514d2a577efcd89e3cadc862ebaf4f4807caeea412b9ca71a20ea899",
  "url": "https://osv.dev/vulnerability/CVE-2026-80685",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mm/util: don't read __page_2 for order-1 folios in snapshot_page()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mm/util: don't read __page_2 for order-1 folios in snapshot_page() snapshot_page() currently reads __page_2 after checking nr_pages > 1, but it should only do so when nr_pages > 2. If an order-1 folio is allocated at the end of a vmemmap section, __page_2 will not exist and reading it will cause a fault. During DLPAR memory remove on a 22 TB ppc64le LPAR, snapshot_page() oopsed on the page isolation path while reading an order-1 folio's __page_2 from an adjacent absent section (unmapped vmemmap). Fix this to avoid reading memmap that doesn't exist (e.g., a vmemmap hole).",
    "evidence": "osv:CVE-2026-80685",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.44",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.8",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-80685",
      "aliases": [
        "CVE-2026-80685"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "fixed": "9668ffe0e2a5e2399dce281620198a2e415871fc"
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "6.12.111"
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                {
                  "fixed": "6.13"
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            },
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "4117738bd42c8ab58090729daf0f8472a936f662"
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          "versions": [
            "v6.12.112",
            "v6.12.111"
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          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.15.0"
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                {
                  "fixed": "6.18.44"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.8"
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80685.json"
          }
        }
      ],
      "modified": "2026-10-08T02:52:03.254437071Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/7441d6348c70738e9ed307510db171c7a9b3f4bf",
        "https://git.kernel.org/stable/c/9668ffe0e2a5e2399dce281620198a2e415871fc",
        "https://git.kernel.org/stable/c/c649324571206a30949765320b91ccdb4c1722dc",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80685.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-80685",
        "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/2026/80xxx/CVE-2026-80685.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-80685",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 98366,
  "published_at": "2026-08-28T06:52:51.305+00:00"
}