nfsd: drop the stateid, not the stateowner, on seqid_op replay retry

{
  "id": "60c1206e9f8fa6fcc82149859477addaa500b57a8219137952926150810c5ab5",
  "url": "https://osv.dev/vulnerability/CVE-2026-89688",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "nfsd: drop the stateid, not the stateowner, on seqid_op replay retry",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: nfsd: drop the stateid, not the stateowner, on seqid_op replay retry In nfs4_preprocess_seqid_op() the stateid is obtained from nfsd4_lookup_stateid(), which holds a reference on the nfs4_stid (sc_count) but takes no reference on the stateowner. openlockstateid() merely casts that stid and likewise takes no reference. When nfsd4_cstate_assign_replay() returns -EAGAIN (the replay owner is being torn down, RP_UNHASHED) it has not taken a stateowner reference on that path. The error handling nevertheless called nfs4_put_stateowner(stp->st_stateowner), dropping an so_count reference the function never acquired -- risking a stateowner refcount underflow and use-after-free -- while leaking the sc_count reference held on the stid. The leaked stid reference can also stall a concurrent nfsd4_close_open_stateid() waiting for sc_count to drop. Drop the reference actually held -- the stid -- before retrying. The stateowner stays alive through the reference held by the stid. This mirrors the open path in nfsd4_process_open1(), where the put balances a reference that path explicitly holds on the stateowner.",
    "evidence": "osv:CVE-2026-89688",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "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": "critical",
    "structured": {
      "id": "CVE-2026-89688",
      "aliases": [
        "CVE-2026-89688"
      ],
      "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": [
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                  "introduced": "eec7620800081e27dbf8019ac2e66259f0d5bf6f"
                },
                {
                  "fixed": "69ed78b6b947c9257213164678b4edf17533093b"
                },
                {
                  "fixed": "00843074d9b84824552c9679d423d29500ca5de0"
                },
                {
                  "fixed": "f7cb90ddc021747fc9abfd4cf5252d425fd34eec"
                },
                {
                  "fixed": "5e4627d3513e60accfce9d5f4c7fa95251ef93d6"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89688.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.10.0"
                },
                {
                  "fixed": "6.12.109"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.50"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89688.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:48.723930635Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/00843074d9b84824552c9679d423d29500ca5de0",
        "https://git.kernel.org/stable/c/5e4627d3513e60accfce9d5f4c7fa95251ef93d6",
        "https://git.kernel.org/stable/c/69ed78b6b947c9257213164678b4edf17533093b",
        "https://git.kernel.org/stable/c/f7cb90ddc021747fc9abfd4cf5252d425fd34eec",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89688.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89688",
        "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-2026-89688.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89688",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 517134,
  "published_at": "2026-09-11T19:46:09.322+00:00"
}