iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry

{
  "id": "a4247492caad64fa4f5eff8f6134fd89c0082150cb4021bdfea28638e49c613f",
  "url": "https://osv.dev/vulnerability/CVE-2026-74439",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry device_pasid_table_teardown() zeroes the 128-bit scalable-mode context entry with context_clear_entry() while the Present bit is still set. This creates a window where the hardware can fetch a torn entry, with some fields already zeroed while Present is still set, leading to unpredictable behavior or spurious faults. The context-cache invalidation is issued only after the entry has been zeroed, and intel_pasid_free_table() then frees the PASID directory pages, so the IOMMU can keep walking a stale Present=1 entry that points at freed memory. While x86 provides strong write ordering, the compiler may reorder the two 64-bit writes to the entry, and the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes. Commit c1e4f1dccbe9d (\"iommu/vt-d: Clear Present bit before tearing down context entry\") fixed this exact pattern in domain_context_clear_one() and the copied-context path, but device_pasid_table_teardown() was not converted. Align it with the \"Guidance to Software for Invalidations\" in the VT-d spec, Section 6.5.3.3, using the same ownership handshake as the sibling fix: clear only the Present bit, flush it to the IOMMU, perform the context-cache invalidation, and only then zero the rest of the entry.",
    "evidence": "osv:CVE-2026-74439",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "6.12.97",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.40",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.5",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-74439",
      "aliases": [
        "CVE-2026-74439"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"
        }
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        {
          "ranges": [
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              "type": "ECOSYSTEM",
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
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          }
        }
      ],
      "modified": "2026-10-28T02:30:22.327044225Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/588718101e8449605f1c7e858fecb7cfa701cdab",
        "https://git.kernel.org/stable/c/7fd4077dc92b91b1b844333c0a06bb9e286db10a",
        "https://git.kernel.org/stable/c/e9e83bcfe37dc719182500dd823c03ab57d934f0",
        "https://git.kernel.org/stable/c/f46452c3df7a8d8a5addc0926e76ef19ea7da0a0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74439.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-74439",
        "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/2026/74xxx/CVE-2026-74439.json"
      }
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    "related_cves": [
      {
        "value": "CVE-2026-74439",
        "evidence": "/id"
      }
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 488770,
  "published_at": "2026-08-15T05:59:36.655+00:00"
}