arm64: contpte: fix set_access_flags() no-op check for SMMU/ATS faults

{
  "id": "e2d1b484a4d5dd66a4764e8b35946b3502a108fc435fdba51e498147e0af6a0d",
  "url": "https://osv.dev/vulnerability/CVE-2026-43486",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "arm64: contpte: fix set_access_flags() no-op check for SMMU/ATS faults",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: arm64: contpte: fix set_access_flags() no-op check for SMMU/ATS faults contpte_ptep_set_access_flags() compared the gathered ptep_get() value against the requested entry to detect no-ops. ptep_get() ORs AF/dirty from all sub-PTEs in the CONT block, so a dirty sibling can make the target appear already-dirty. When the gathered value matches entry, the function returns 0 even though the target sub-PTE still has PTE_RDONLY set in hardware. For a CPU with FEAT_HAFDBS this gathered view is fine, since hardware may set AF/dirty on any sub-PTE and CPU TLB behavior is effectively gathered across the CONT range. But page-table walkers that evaluate each descriptor individually (e.g. a CPU without DBM support, or an SMMU without HTTU, or with HA/HD disabled in CD.TCR) can keep faulting on the unchanged target sub-PTE, causing an infinite fault loop. Gathering can therefore cause false no-ops when only a sibling has been updated: - write faults: target still has PTE_RDONLY (needs PTE_RDONLY cleared) - read faults: target still lacks PTE_AF Fix by checking each sub-PTE against the requested AF/dirty/write state (the same bits consumed by __ptep_set_access_flags()), using raw per-PTE values rather than the gathered ptep_get() view, before returning no-op. Keep using the raw target PTE for the write-bit unfold decision. Per Arm ARM (DDI 0487) D8.7.1 (\"The Contiguous bit\"), any sub-PTE in a CONT range may become the effecti",
    "evidence": "osv:CVE-2026-43486",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.78",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.19",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.9",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-43486",
      "aliases": [
        "CVE-2026-43486"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "4602e5757bcceb231c3a13c36c373ad4a750eddb"
                },
                {
                  "fixed": "05d239f2c95e66e27e7fb4e99ee07eb56e3e34b0"
                },
                {
                  "fixed": "6f92a7a8b48a523f910ef25dd83808710724f59b"
                },
                {
                  "fixed": "09d620555e59768776090073a2c59d2bc8506eb3"
                },
                {
                  "fixed": "97c5550b763171dbef61e6239cab372b9f9cd4a2"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43486.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.9.0"
                },
                {
                  "fixed": "6.12.78"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.19"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "6.19.9"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43486.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:51.403623353Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/05d239f2c95e66e27e7fb4e99ee07eb56e3e34b0",
        "https://git.kernel.org/stable/c/09d620555e59768776090073a2c59d2bc8506eb3",
        "https://git.kernel.org/stable/c/6f92a7a8b48a523f910ef25dd83808710724f59b",
        "https://git.kernel.org/stable/c/97c5550b763171dbef61e6239cab372b9f9cd4a2",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43486.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-43486",
        "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/2026/43xxx/CVE-2026-43486.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-43486",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 519615,
  "published_at": "2026-05-13T15:08:32.085+00:00"
}