nfsd: fix cpntf publish race in nfs4_init_cp_state

{
  "id": "99f876d028cc08c7d4b09077e5896d02cf7ce06e067bf4cd1ca89af77bbe3246",
  "url": "https://osv.dev/vulnerability/CVE-2026-89684",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "nfsd: fix cpntf publish race in nfs4_init_cp_state",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: nfsd: fix cpntf publish race in nfs4_init_cp_state nfs4_alloc_init_cpntf_state() published the new cpntf entry into the s2s_cp_stateids IDR (with cs_type set) in one s2s_cp_lock section, then took the lock again to list_add() it onto p_stid->sc_cp_list. In the gap the entry is reachable by so_id but cp_list is still {NULL,NULL} from kzalloc. A racing OFFLOAD_CANCEL (so_id is echoed to the client as cnr_stateid, so any NFSv4.2 client can drive it) reaches manage_cpntf_state() -> _free_cpntf_state_locked() and does list_del() on the zeroed list_head, oopsing the server. Fold the cs_type assignment and the list_add() into the same critical section as idr_alloc_cyclic(), so a concurrent lookup either misses the entry or sees a fully linked cp_list. INIT_LIST_HEAD() the entry after allocation and switch _free_cpntf_state_locked() to list_del_init() so a stale unlink is a no-op. nfs4_init_copy_state() passes NULL p_stid and skips the list_add, preserving NFS4_COPY_STID semantics.",
    "evidence": "osv:CVE-2026-89684",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.270",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.221",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.188",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.157",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.109",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.50",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-89684",
      "aliases": [
        "CVE-2026-89684"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
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              "type": "GIT",
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                {
                  "fixed": "6ac469a274e3c7d87fc46ba46d83b95009680407"
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                {
                  "fixed": "8eeca993357a0bc35aaefebfd7462ac7b0a21d9a"
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                {
                  "fixed": "bfeac42d9074e539bacd1898dd8c14b7f5776620"
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        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "5.6.0"
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89684.json"
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      ],
      "modified": "2026-10-28T02:30:23.166574195Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/21d6c5957f5ca97d7352e60f55ea412beb9419f5",
        "https://git.kernel.org/stable/c/63e18fc65587fd3f7b4c6d70e96d32fc41d82ba3",
        "https://git.kernel.org/stable/c/6ac469a274e3c7d87fc46ba46d83b95009680407",
        "https://git.kernel.org/stable/c/8eeca993357a0bc35aaefebfd7462ac7b0a21d9a",
        "https://git.kernel.org/stable/c/a631a26a8777bb235eabd478bbbaf26a4db750bf",
        "https://git.kernel.org/stable/c/be3a5c1d857b0dcbc11796cea603ef25834f75b2",
        "https://git.kernel.org/stable/c/bfeac42d9074e539bacd1898dd8c14b7f5776620",
        "https://git.kernel.org/stable/c/c7270f62e7a05a2ee68aa2b74262b658a14463bd",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89684.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89684",
        "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/2026/89xxx/CVE-2026-89684.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89684",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 489716,
  "published_at": "2026-09-11T19:46:06.374+00:00"
}