---
id: CVE-2026-89663
title: 'nfsd: revoke copy-notify stateids before dropping their reference'
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…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-825
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 <
    5f00e0ab4de45d4f9e4bd0883cf2517acf63fc0d
  - >-
    Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 <
    06a62f6dbc60791f4229c6950b1eec6b18df9af1
  - >-
    Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 <
    a1fca0f7bbb7b100a39c7ba8dd7922c87c4237a3
  - >-
    Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 <
    caddbeffab1eaba1d2bcf5ceda35547863466705
  - >-
    Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 <
    6b8149448cdcb476fba4559d1ecc247efee9971b
  - >-
    Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 <
    b56d2c5f01cddbeca7d11cce81d97db4ec9a464f
  - >-
    Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 <
    ff8a3cff02b92b2a82f1a9876038fcf953ae9c25
  - >-
    Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 <
    3b0c3595db99bb4bebd7c8aa8a36f3c50e411bb7
  - Linux 5.6
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:50:34.792Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89663'
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'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89663.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89663'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532231'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89663'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89663'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89663.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00455
epssPercentile: 0.39353
scores:
  cna: 8.8
  vendor: 7
ingestedAt: '2026-09-14T15:23:07.450Z'
---

## Overview

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).

## Affected

- `Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 < 5f00e0ab4de45d4f9e4bd0883cf2517acf63fc0d`
- `Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 < 06a62f6dbc60791f4229c6950b1eec6b18df9af1`
- `Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 < a1fca0f7bbb7b100a39c7ba8dd7922c87c4237a3`
- `Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 < caddbeffab1eaba1d2bcf5ceda35547863466705`
- `Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 < 6b8149448cdcb476fba4559d1ecc247efee9971b`
- `Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 < b56d2c5f01cddbeca7d11cce81d97db4ec9a464f`
- `Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 < ff8a3cff02b92b2a82f1a9876038fcf953ae9c25`
- `Linux >= 624322f1adc58acd0b69f77a6ddc764207e97241 < 3b0c3595db99bb4bebd7c8aa8a36f3c50e411bb7`
- `Linux 5.6`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-27 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89663.json)