---
id: CVE-2026-22980
title: 'nfsd: provide locking for v4_end_grace'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nfsd: provide locking for v4_end_grace

  Writing to v4_end_grace can race with server shutdown and result in
  memory being accessed after it was freed - reclaim_str_hasht…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 <
    ca97360860eb02e3ae4ba42c19b439a0fcecbf06
  - >-
    Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 <
    e8bfa2401d4c51eca6e48e9b33c798828ca9df61
  - >-
    Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 <
    34eb22836e0cdba093baac66599d68c4cd245a9d
  - >-
    Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 <
    06600719d0f7a723811c45e4d51f5b742f345309
  - >-
    Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 <
    ba4811c8b433bfa681729ca42cc62b6034f223b0
  - >-
    Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 <
    53f07d095e7e680c5e4569a55a019f2c0348cdc6
  - >-
    Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 <
    2857bd59feb63fcf40fe4baf55401baea6b4feb4
  - Linux 3.18
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-06-16T20:36:55.336499Z'
published: '2026-01-23'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:44:27.990Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-22980'
references:
  - url: 'https://git.kernel.org/stable/c/ca97360860eb02e3ae4ba42c19b439a0fcecbf06'
  - url: 'https://git.kernel.org/stable/c/e8bfa2401d4c51eca6e48e9b33c798828ca9df61'
  - url: 'https://git.kernel.org/stable/c/34eb22836e0cdba093baac66599d68c4cd245a9d'
  - url: 'https://git.kernel.org/stable/c/06600719d0f7a723811c45e4d51f5b742f345309'
  - url: 'https://git.kernel.org/stable/c/ba4811c8b433bfa681729ca42cc62b6034f223b0'
  - url: 'https://git.kernel.org/stable/c/53f07d095e7e680c5e4569a55a019f2c0348cdc6'
  - url: 'https://git.kernel.org/stable/c/2857bd59feb63fcf40fe4baf55401baea6b4feb4'
tags:
  - cve.org
epss: 0.00149
epssPercentile: 0.04493
ingestedAt: '2026-09-08T15:33:26.994Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

nfsd: provide locking for v4_end_grace

Writing to v4_end_grace can race with server shutdown and result in
memory being accessed after it was freed - reclaim_str_hashtbl in
particularly.

We cannot hold nfsd_mutex across the nfsd4_end_grace() call as that is
held while client_tracking_op->init() is called and that can wait for
an upcall to nfsdcltrack which can write to v4_end_grace, resulting in a
deadlock.

nfsd4_end_grace() is also called by the landromat work queue and this
doesn't require locking as server shutdown will stop the work and wait
for it before freeing anything that nfsd4_end_grace() might access.

However, we must be sure that writing to v4_end_grace doesn't restart
the work item after shutdown has already waited for it.  For this we
add a new flag protected with nn->client_lock.  It is set only while it
is safe to make client tracking calls, and v4_end_grace only schedules
work while the flag is set with the spinlock held.

So this patch adds a nfsd_net field "client_tracking_active" which is
set as described.  Another field "grace_end_forced", is set when
v4_end_grace is written.  After this is set, and providing
client_tracking_active is set, the laundromat is scheduled.
This "grace_end_forced" field bypasses other checks for whether the
grace period has finished.

This resolves a race which can result in use-after-free.

## Affected

- `Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 < ca97360860eb02e3ae4ba42c19b439a0fcecbf06`
- `Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 < e8bfa2401d4c51eca6e48e9b33c798828ca9df61`
- `Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 < 34eb22836e0cdba093baac66599d68c4cd245a9d`
- `Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 < 06600719d0f7a723811c45e4d51f5b742f345309`
- `Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 < ba4811c8b433bfa681729ca42cc62b6034f223b0`
- `Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 < 53f07d095e7e680c5e4569a55a019f2c0348cdc6`
- `Linux >= 7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 < 2857bd59feb63fcf40fe4baf55401baea6b4feb4`
- `Linux 3.18`

## Remediation

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