NFSv4/flexfiles: reject zero filehandle version count

{
  "id": "39e5accdee938927f931db7c383bf65c0ef8a99cd31d52ffe969dc238acccfba",
  "url": "https://osv.dev/vulnerability/CVE-2026-53392",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "NFSv4/flexfiles: reject zero filehandle version count",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: NFSv4/flexfiles: reject zero filehandle version count ff_layout_alloc_lseg() decodes the filehandle-version array count from the flexfiles layout body. The value is used as the count for kzalloc_objs(), and the current code only rejects NULL. A zero count yields ZERO_SIZE_PTR, which can be stored in dss_info->fh_versions even though later flexfiles paths assume that at least one filehandle version exists. Reject fh_count == 0 before the allocation, matching the existing zero version_count validation in the flexfiles GETDEVICEINFO parser. A QEMU/KASAN run with a malformed flexfiles layout hit: KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:ff_layout_encode_ff_layoutupdate.isra.0+0x15f/0x750 ff_layout_encode_layoutreturn+0x683/0x970 nfs4_xdr_enc_layoutreturn+0x278/0x3a0 Kernel panic - not syncing: Fatal exception The patched kernel rejects the malformed layout without KASAN/oops/panic, and a valid fh_count=1 regression still opens, reads, and unmounts cleanly.",
    "evidence": "osv:CVE-2026-53392",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "evidence": "/affected/1/ranges"
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        "affected_versions": []
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    "severity": "high",
    "structured": {
      "id": "CVE-2026-53392",
      "aliases": [
        "CVE-2026-53392"
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      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
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      ],
      "modified": "2026-10-28T02:30:31.551590707Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/18cc6d57a14fa65ab2a2b52279f549041c4bc9cf",
        "https://git.kernel.org/stable/c/2131ed64b767ffa8bcdb3677d90f3964e39aabc8",
        "https://git.kernel.org/stable/c/2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2",
        "https://git.kernel.org/stable/c/7779c85028a0676fb190cde4f0c540f4f8e97761",
        "https://git.kernel.org/stable/c/9033591535c066726f5b505126ccb4068b98fa4f",
        "https://git.kernel.org/stable/c/be7829715e341b42846437dd9e721005db59f0cc",
        "https://git.kernel.org/stable/c/d8c90c7cc061265d5f2813a1f5c82ef2f4707e67",
        "https://git.kernel.org/stable/c/eeabb9020721db6bc132e68eeae380b8d4fb4b04",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53392.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-53392",
        "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/2026/53xxx/CVE-2026-53392.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-53392",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 498699,
  "published_at": "2026-07-19T12:01:56.101+00:00"
}