CVE-2026-80685 (GCVE-0-2026-80685)

Vulnerability from cvelistv5 – Published: 2026-08-28 06:52 – Updated: 2026-08-29 06:22
VLAI
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).
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 31a31da8a6187f1e5448ec73222e01d7d3fed4aa , < 9668ffe0e2a5e2399dce281620198a2e415871fc (git)
Affected: 31a31da8a6187f1e5448ec73222e01d7d3fed4aa , < c649324571206a30949765320b91ccdb4c1722dc (git)
Affected: 31a31da8a6187f1e5448ec73222e01d7d3fed4aa , < 7441d6348c70738e9ed307510db171c7a9b3f4bf (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.18.44 , ≤ 6.18.* (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/util: don\u0027t read __page_2 for order-1 folios in snapshot_page()\n\nsnapshot_page() currently reads __page_2 after checking nr_pages \u003e 1, but\nit should only do so when nr_pages \u003e 2.\n\nIf an order-1 folio is allocated at the end of a vmemmap section,\n__page_2 will not exist and reading it will cause a fault.\n\nDuring DLPAR memory remove on a 22 TB ppc64le LPAR, snapshot_page() oopsed\non the page isolation path while reading an order-1 folio\u0027s __page_2 from\nan adjacent absent section (unmapped vmemmap).\n\nFix this to avoid reading memmap that doesn\u0027t exist (e.g., a vmemmap\nhole)."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
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              "lang": "en",
              "value": "AV:L - Reachable via local read(2) on /proc/kpageflags or /proc/kpagecount (kpage_read\u2192stable_page_flags/get_kpage_count\u2192snapshot_page); the reported production crash also occurs on the memory-hotplug page-isolation dump_page path during offline_pages/DLPAR, with no network or physical-bus entry point.\nAC:L - A container/user-namespace root can sequentially scan PFNs via /proc/kpageflags until snapshot_page hits an order-1 folio at a vmemmap section boundary; on large SPARSEMEM_VMEMMAP systems such folios exist naturally (22 TB ppc64le LPAR oops) without races or attacker-uncontrollable timing.\nPR:L - /proc/kpage* is mode 0400 (root-only); exploitation needs only namespace/container root or CAP_SYS_ADMIN in a user namespace to read host proc on typical Docker/K8s/cloud nodes\u2014not init-namespace root; the DLPAR offline path needs admin but is not the lowest-privilege vector.\nUI:N - The attacker performs their own /proc/kpageflags reads or triggers kernel debug dumps; no separate victim action such as opening a file, mounting a filesystem, or approving a prompt is required beyond having local proc access.\nS:U - Impact is a kernel oops/panic within the host kernel security boundary; there is no VM escape, IOMMU bypass, or cross-authority resource access beyond crashing or destabilizing the shared kernel.\nC:H - snapshot_page() performs memcpy of a full struct page from foliop-\u003e__page_2 when only two pages are valid for order-1 folios, reading beyond allocated vmemmap into an unmapped hole; this out-of-bounds kernel read can expose adjacent mapped memmap bytes to the snapshot buffer on some layouts before faulting.\nI:N - The defect is a read past valid folio memmap that page-faults in kernel mode; memcpy only fills a local page_snapshot buffer and does not corrupt kernel objects, enable arbitrary writes, or provide a control-flow hijack primitive.\nA:H - Reading absent vmemmap for order-1 folios at section boundaries causes a supervisor page fault and kernel oops, as demonstrated during DLPAR memory remove on ppc64le; repeated /proc/kpageflags scanning can reliably panic or hang large-memory cloud/LPAR hosts."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-29T06:22:12.733Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
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          "url": "https://git.kernel.org/stable/c/9668ffe0e2a5e2399dce281620198a2e415871fc"
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        {
          "url": "https://git.kernel.org/stable/c/c649324571206a30949765320b91ccdb4c1722dc"
        },
        {
          "url": "https://git.kernel.org/stable/c/7441d6348c70738e9ed307510db171c7a9b3f4bf"
        }
      ],
      "title": "mm/util: don\u0027t read __page_2 for order-1 folios in snapshot_page()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80685",
    "datePublished": "2026-08-28T06:52:51.305Z",
    "dateReserved": "2026-08-26T14:34:25.784Z",
    "dateUpdated": "2026-08-29T06:22:12.733Z",
    "state": "PUBLISHED"
  },
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    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-09-01T12:40:58+00:00",
      "cve": "CVE-2026-80685",
      "id": "CVE-2026-80685",
      "initial_release_date": "2026-08-28T00:00:00+00:00",
      "product_status:known_affected": "90",
      "product_status:known_not_affected": "184",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: mm/util: don\u0027t read __page_2 for order-1 folios in snapshot_page()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80685.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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