nfsd: fix layout fence worker double-reference race

{
  "id": "6b3c048bc21967b7e01114d202dcc040023b000108116721da718a6516527fd0",
  "url": "https://osv.dev/vulnerability/CVE-2026-89681",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "nfsd: fix layout fence worker double-reference race",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: nfsd: fix layout fence worker double-reference race The workqueue core clears WORK_STRUCT_PENDING before the callback is invoked, so delayed_work_pending() in lm_breaker_timedout() can return false while the fence worker is already running. This lets the breaker take a duplicate sc_count reference and schedule a new worker that coalesces with the in-progress one. The extra reference is never put, leaking the layout stateid. Replace the racy delayed_work_pending() check with an ls_fence_inflight boolean set atomically with refcount_inc_not_zero() under ls_lock, and cleared under ls_lock before the final nfs4_put_stid() on the dispose path; the retry path intentionally retains it. Remove the self-rearm mod_delayed_work() at the top of the worker.",
    "evidence": "osv:CVE-2026-89681",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-89681",
      "aliases": [
        "CVE-2026-89681"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "f52792f484ba2316853736856dde19b7e7458861"
                },
                {
                  "fixed": "a278d361e0e8f242211891193d56483a7a9f47a8"
                },
                {
                  "fixed": "8580571227451384399b3fa53fcde19848c48e5a"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89681.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "7.1.0"
                },
                {
                  "fixed": "7.2.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89681.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:45.850029202Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/8580571227451384399b3fa53fcde19848c48e5a",
        "https://git.kernel.org/stable/c/a278d361e0e8f242211891193d56483a7a9f47a8",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89681.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89681",
        "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-2026-89681.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89681",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 513958,
  "published_at": "2026-09-11T19:46:04.121+00:00"
}