CVE-2026-89663 (GCVE-0-2026-89663)
Vulnerability from cvelistv5
Published
2026-09-11 19:45
Modified
2026-10-19 08:50
Severity ?
8.8 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: revoke copy-notify stateids before dropping their reference Copy-notify stateids live in the s2s_cp_stateids IDR and on their parent stid's sc_cp_list, pinned by a single membership reference. _free_cpntf_state_locked() only unlinks an entry once its refcount reaches zero, so any revoke path that runs while a concurrent find_cpntf_state()/manage_cpntf_state() holder has elevated cs_count drops the reference without unlinking, leaving the entry discoverable with its membership reference already consumed. A second revoke or a laundromat tick then frees it while the reader still holds the pointer -- a KASAN-detectable use-after-free at the reader's nfs4_put_cpntf_state(). This affected all three revoke paths: - The parent-stid drain (nfs4_free_cpntf_statelist()) repeatedly called _free_cpntf_state_locked() on the first list entry; a holder that had bumped cs_count made it return early, so the next iteration re-decremented and burned the holder's reference. - OFFLOAD_CANCEL (manage_cpntf_state()) and laundromat expiry likewise used _free_cpntf_state_locked() and could drop 2->1 without unlinking. Add revoke_cpntf_state_locked(), which unhashes the entry from the IDR and sc_cp_list first (deferring the final free to any holder), and use it from all three revoke paths. The drain now walks with list_for_each_entry_safe() and revokes each entry unconditionally, so it terminates in one pass per entry regardless of cs_count. The unhash is gated on !list_empty(&cps->cp_list); the idr_remove() gate matters because idr_alloc_cyclic() may have recycled the so_id by then. Keep _free_cpntf_state_locked() for the reference-holder put path only, where a concurrent revoke may already have unlinked the entry (its list_del_init() then a no-op).
References
Impacted products
Vendor Product Version
Linux Linux Version: 624322f1adc58acd0b69f77a6ddc764207e97241
Version: 624322f1adc58acd0b69f77a6ddc764207e97241
Version: 624322f1adc58acd0b69f77a6ddc764207e97241
Version: 624322f1adc58acd0b69f77a6ddc764207e97241
Version: 624322f1adc58acd0b69f77a6ddc764207e97241
Version: 624322f1adc58acd0b69f77a6ddc764207e97241
Version: 624322f1adc58acd0b69f77a6ddc764207e97241
Version: 624322f1adc58acd0b69f77a6ddc764207e97241
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{
  "containers": {
    "cna": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4state.c"
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          "vendor": "Linux",
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: revoke copy-notify stateids before dropping their reference\n\nCopy-notify stateids live in the s2s_cp_stateids IDR and on their parent\nstid\u0027s sc_cp_list, pinned by a single membership reference.\n_free_cpntf_state_locked() only unlinks an entry once its refcount reaches\nzero, so any revoke path that runs while a concurrent\nfind_cpntf_state()/manage_cpntf_state() holder has elevated cs_count drops\nthe reference without unlinking, leaving the entry discoverable with its\nmembership reference already consumed. A second revoke or a laundromat tick\nthen frees it while the reader still holds the pointer -- a\nKASAN-detectable use-after-free at the reader\u0027s nfs4_put_cpntf_state().\n\nThis affected all three revoke paths:\n\n  - The parent-stid drain (nfs4_free_cpntf_statelist()) repeatedly called\n    _free_cpntf_state_locked() on the first list entry; a holder that had\n    bumped cs_count made it return early, so the next iteration\n    re-decremented and burned the holder\u0027s reference.\n\n  - OFFLOAD_CANCEL (manage_cpntf_state()) and laundromat expiry likewise\n    used _free_cpntf_state_locked() and could drop 2-\u003e1 without unlinking.\n\nAdd revoke_cpntf_state_locked(), which unhashes the entry from the IDR and\nsc_cp_list first (deferring the final free to any holder), and use it from\nall three revoke paths. The drain now walks with list_for_each_entry_safe()\nand revokes each entry unconditionally, so it terminates in one pass per\nentry regardless of cs_count. The unhash is gated on\n!list_empty(\u0026cps-\u003ecp_list); the idr_remove() gate matters because\nidr_alloc_cyclic() may have recycled the so_id by then. Keep\n_free_cpntf_state_locked() for the reference-holder put path only, where a\nconcurrent revoke may already have unlinked the entry (its list_del_init()\nthen a no-op)."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The flaw is in the in-kernel NFS server (nfsd); COPY_NOTIFY, READ using a copy-notify stateid, CLOSE, and OFFLOAD_CANCEL are processed from NFSv4.2 compounds over TCP/2049, so a remote NFS client reaches the use-after-free over the network.\nAC:L - A malicious client fully controls both sides of the race: one compound READs with the copy-notify stateid so find_cpntf_state holds a cs_count reference while a concurrent CLOSE or OFFLOAD_CANCEL drains it; nfs4_free_cpntf_statelist then double-decrements and kfree\u0027s the still-linked object with no condition outside attacker control.\nPR:L - The attacker must be an established NFSv4.2 client of an export holding a valid open, lock, or delegation stateid to issue COPY_NOTIFY, which is authenticated low-privilege service access rather than a pre-authentication nfsd path.\nUI:N - No victim action is required; the attacking client drives COPY_NOTIFY, the concurrent READ that holds the cpntf reference, and CLOSE or OFFLOAD_CANCEL on its own NFS connections.\nS:U - The use-after-free corrupts kernel slab memory within the host nfsd security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - Use-after-free of struct nfs4_cpntf_state lets a concurrent find_cpntf_state reader dereference a kfree\u0027d object; heap reuse of that slab gives the attacker control over freed contents, enabling arbitrary kernel memory disclosure.\nI:H - After the drain kfree, the holder still writes cpntf_time and later nfs4_put_cpntf_state runs _free_cpntf_state_locked on the freed object, a use-after-free write primitive usable for controlled memory modification and control-flow hijacking.\nA:H - The KASAN-detectable use-after-free at nfs4_put_cpntf_state oopses or panics nfsd worker threads, fully disrupting availability of the NFS server host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:50:34.792Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/5f00e0ab4de45d4f9e4bd0883cf2517acf63fc0d"
        },
        {
          "url": "https://git.kernel.org/stable/c/06a62f6dbc60791f4229c6950b1eec6b18df9af1"
        },
        {
          "url": "https://git.kernel.org/stable/c/a1fca0f7bbb7b100a39c7ba8dd7922c87c4237a3"
        },
        {
          "url": "https://git.kernel.org/stable/c/caddbeffab1eaba1d2bcf5ceda35547863466705"
        },
        {
          "url": "https://git.kernel.org/stable/c/6b8149448cdcb476fba4559d1ecc247efee9971b"
        },
        {
          "url": "https://git.kernel.org/stable/c/b56d2c5f01cddbeca7d11cce81d97db4ec9a464f"
        },
        {
          "url": "https://git.kernel.org/stable/c/ff8a3cff02b92b2a82f1a9876038fcf953ae9c25"
        },
        {
          "url": "https://git.kernel.org/stable/c/3b0c3595db99bb4bebd7c8aa8a36f3c50e411bb7"
        }
      ],
      "title": "nfsd: revoke copy-notify stateids before dropping their reference",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89663",
    "datePublished": "2026-09-11T19:45:50.577Z",
    "dateReserved": "2026-09-11T19:38:34.744Z",
    "dateUpdated": "2026-10-19T08:50:34.792Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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