---
id: CVE-2026-93221
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nfsd: convert nfsd_net boolean flags to unsigned long flags word

  nfsd_net contains several boolean fields that are accessed from
  concurrent contexts without serializat…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nfsd: convert nfsd_net boolean flags to unsigned long flags word

  nfsd_net contains several boolean fields that are accessed from
  concurrent contexts without serializat…
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 362063a595be959bc08f4163e6405a0266740091 <
    df5922fe09a8131c793ffa86adf204999b0470f8
  - >-
    Linux >= 362063a595be959bc08f4163e6405a0266740091 <
    11a5fe42e1811f793e04ef885b639ea7668f439d
  - Linux 5.2
published: '2026-09-24'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T05:17:00.150'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93221'
references:
  - url: 'https://git.kernel.org/stable/c/11a5fe42e1811f793e04ef885b639ea7668f439d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/df5922fe09a8131c793ffa86adf204999b0470f8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-24T15:45:56.669Z'
---

## Overview

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

nfsd: convert nfsd_net boolean flags to unsigned long flags word

nfsd_net contains several boolean fields that are accessed from
concurrent contexts without serialization.  In particular,
nfsd4_end_grace() guards its drain path with a plain bool:

    if (nn->grace_ended)
            return;
    nn->grace_ended = true;

The read and the write are independent, and nothing in struct
nfsd_net serializes them.  At least two contexts can reach this
code with no lock held:

    laundromat path
      laundry_wq kworker
        nfs4_laundromat()
          nfsd4_end_grace()

    RECLAIM_COMPLETE path
      nfsd compound kthread
        nfsd4_reclaim_complete()
          inc_reclaim_complete()
            nfsd4_end_grace()

Both callers can observe grace_ended == false on different CPUs,
both store true, and both proceed into nfsd4_record_grace_done(),
which invokes the active client_tracking_ops->grace_done callback.
For tracking ops that drain reclaim_str_hashtbl (legacy_tracking_ops
via nfsd4_recdir_purge_old, and the cld v1+ ops via
nfsd4_cld_grace_done), grace_done calls nfs4_release_reclaim(),
which walks every bucket of reclaim_str_hashtbl with no lock and
calls nfs4_remove_reclaim_record() (list_del + kfree) on each
entry.  Two concurrent walkers corrupt the list and double-free
every nfs4_client_reclaim.  A concurrent nfsd4_find_reclaim_client()
iterating the same bucket reads through freed memory.

A third call site exists in nfs4_state_start_net() on the
skip_grace startup path, but it runs under nfsd_mutex before any
client has connected and before the laundromat's first delayed
work fires, so it cannot race with the two callers above.

Replace the scattered boolean fields in nfsd_net with a single
unsigned long flags word and an enum nfsd_net_flag for the bit
positions.  The grace_ended race is fixed by using
test_and_set_bit(), which is atomic on all architectures.  The
remaining flags (grace_end_forced, in_grace, somebody_reclaimed,
track_reclaim_completes, nfsd_net_up, lockd_up) are converted to
use test_bit/set_bit/clear_bit for consistency.  This avoids
sub-word cmpxchg issues on architectures like Hexagon that only
support word-sized atomic operations.

## Remediation

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