ntfs: validate usa_ofs before preserving the update sequence number

{
  "id": "fe38e6e9e9777666d82b02abf048f73830f64a7404323d8740b181489323f61c",
  "url": "https://osv.dev/vulnerability/CVE-2026-90117",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ntfs: validate usa_ofs before preserving the update sequence number",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ntfs: validate usa_ofs before preserving the update sequence number When ntfs_mft_record_alloc() reuses a free mft record it reads the old update sequence number straight from the on-disk record: usn = *(__le16 *)((u8 *)m + le16_to_cpu(m->usa_ofs)); Here m points into the raw $MFT page-cache folio, which still holds unvalidated, MST-protected bytes: the folio is read by a plain iomap_read_folio() and neither post_read_mst_fixup() nor ntfs_mft_record_check() has run on it (both work on private copies). m->usa_ofs is therefore an untrusted u16, and a corrupted record can put it past the end of the record so the two-byte read lands outside the folio. Reading such a record while creating a file gives, under KASAN: BUG: KASAN: use-after-free in ntfs_mft_record_alloc+... Read of size 2 at addr ... ntfs_mft_record_alloc -> __ntfs_create -> ntfs_create -> path_openat Only preserve the old update sequence number when usa_ofs is even and in range, mirroring the check ntfs_mft_record_check() already applies; otherwise leave usn zero, which the existing restore below skips.",
    "evidence": "osv:CVE-2026-90117",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.2.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-90117",
      "aliases": [
        "CVE-2026-90117"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "495e90fa334828d4119061e2726af51d0a0fb4ed"
                },
                {
                  "fixed": "ea5a3c30710710c1dc5e483d3313309ec2e868f7"
                },
                {
                  "fixed": "81684340963da2e898eabb8c1e274433d9375bc6"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90117.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "7.1.0"
                },
                {
                  "fixed": "7.2.6"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90117.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:41.318797964Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/81684340963da2e898eabb8c1e274433d9375bc6",
        "https://git.kernel.org/stable/c/ea5a3c30710710c1dc5e483d3313309ec2e868f7",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90117.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-90117",
        "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/2026/90xxx/CVE-2026-90117.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-90117",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 509151,
  "published_at": "2026-09-17T16:06:22.705+00:00"
}