linux-cve-announce - CVE-2026-22989: nfsd: check that server is running in unlock

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Message-ID: <2026012350-CVE-2026-22989-06be@gregkh>
Date: Fri, 23 Jan 2026 16:25:00 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-22989: nfsd: check that server is running in unlock_filesystem

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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

nfsd: check that server is running in unlock_filesystem

If we are trying to unlock the filesystem via an administrative
interface and nfsd isn't running, it crashes the server. This
happens currently because nfsd4_revoke_states() access state
structures (eg., conf_id_hashtbl) that has been freed as a part
of the server shutdown.

[   59.465072] Call trace:
[   59.465308]  nfsd4_revoke_states+0x1b4/0x898 [nfsd] (P)
[   59.465830]  write_unlock_fs+0x258/0x440 [nfsd]
[   59.466278]  nfsctl_transaction_write+0xb0/0x120 [nfsd]
[   59.466780]  vfs_write+0x1f0/0x938
[   59.467088]  ksys_write+0xfc/0x1f8
[   59.467395]  __arm64_sys_write+0x74/0xb8
[   59.467746]  invoke_syscall.constprop.0+0xdc/0x1e8
[   59.468177]  do_el0_svc+0x154/0x1d8
[   59.468489]  el0_svc+0x40/0xe0
[   59.468767]  el0t_64_sync_handler+0xa0/0xe8
[   59.469138]  el0t_64_sync+0x1ac/0x1b0

Ensure this can't happen by taking the nfsd_mutex and checking that
the server is still up, and then holding the mutex across the call to
nfsd4_revoke_states().

The Linux kernel CVE team has assigned CVE-2026-22989 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.9 with commit 1ac3629bf012592cb0320e52a1cceb319a05ad17 and fixed in 6.12.66 with commit d95499900fe52f3d461ed26b7a30bebea8f12914
	Issue introduced in 6.9 with commit 1ac3629bf012592cb0320e52a1cceb319a05ad17 and fixed in 6.18.6 with commit e06c9f6c0f554148d4921c2a15bd054260a054ac
	Issue introduced in 6.9 with commit 1ac3629bf012592cb0320e52a1cceb319a05ad17 and fixed in 6.19-rc5 with commit d0424066fcd294977f310964bed6f2a487fa4515

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-22989
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/nfsd/nfs4state.c
	fs/nfsd/nfsctl.c
	fs/nfsd/state.h


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/d95499900fe52f3d461ed26b7a30bebea8f12914
	https://git.kernel.org/stable/c/e06c9f6c0f554148d4921c2a15bd054260a054ac
	https://git.kernel.org/stable/c/d0424066fcd294977f310964bed6f2a487fa4515