drm/xe/hmm: Don't dereference struct page pointers without notifier lock

{
  "id": "15f737b9e33d609945d13889b9425975ab40a176165f6ed3a8e18060824b3486",
  "url": "https://osv.dev/vulnerability/CVE-2025-21939",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "drm/xe/hmm: Don't dereference struct page pointers without notifier lock",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: drm/xe/hmm: Don't dereference struct page pointers without notifier lock The pnfs that we obtain from hmm_range_fault() point to pages that we don't have a reference on, and the guarantee that they are still in the cpu page-tables is that the notifier lock must be held and the notifier seqno is still valid. So while building the sg table and marking the pages accesses / dirty we need to hold this lock with a validated seqno. However, the lock is reclaim tainted which makes sg_alloc_table_from_pages_segment() unusable, since it internally allocates memory. Instead build the sg-table manually. For the non-iommu case this might lead to fewer coalesces, but if that's a problem it can be fixed up later in the resource cursor code. For the iommu case, the whole sg-table may still be coalesced to a single contigous device va region. This avoids marking pages that we don't own dirty and accessed, and it also avoid dereferencing struct pages that we don't own. v2: - Use assert to check whether hmm pfns are valid (Matthew Auld) - Take into account that large pages may cross range boundaries (Matthew Auld) v3: - Don't unnecessarily check for a non-freed sg-table. (Matthew Auld) - Add a missing up_read() in an error path. (Matthew Auld) (cherry picked from commit ea3e66d280ce2576664a862693d1da8fd324c317)",
    "evidence": "osv:CVE-2025-21939",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.19",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.13.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2025-21939",
      "aliases": [
        "CVE-2025-21939"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
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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": "81e058a3e7fd8593d076b4f26f7b8bb49f1d61e3"
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                {
                  "fixed": "2a24c98f0e4cc994334598d4f3a851972064809d"
                },
                {
                  "fixed": "f9326f529da7298a95643c3267f1c0fdb0db55eb"
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                {
                  "fixed": "0a98219bcc961edd3388960576e4353e123b4a51"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21939.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.10.0"
                },
                {
                  "fixed": "6.12.19"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.13.7"
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-21939.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:25.305113701Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0a98219bcc961edd3388960576e4353e123b4a51",
        "https://git.kernel.org/stable/c/2a24c98f0e4cc994334598d4f3a851972064809d",
        "https://git.kernel.org/stable/c/f9326f529da7298a95643c3267f1c0fdb0db55eb",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21939.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-21939",
        "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/2025/21xxx/CVE-2025-21939.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-21939",
        "evidence": "/id"
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    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 491750,
  "published_at": "2025-04-01T15:41:05.393+00:00"
}