From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-89681: nfsd: fix layout fence worker double-reference race
Date: Fri, 11 Sep 2026 21:46:10 +0200 [thread overview]
Message-ID: <2026091151-CVE-2026-89681-2a18@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
nfsd: fix layout fence worker double-reference race
The workqueue core clears WORK_STRUCT_PENDING before the callback
is invoked, so delayed_work_pending() in lm_breaker_timedout() can
return false while the fence worker is already running. This lets
the breaker take a duplicate sc_count reference and schedule a new
worker that coalesces with the in-progress one. The extra reference
is never put, leaking the layout stateid.
Replace the racy delayed_work_pending() check with an
ls_fence_inflight boolean set atomically with
refcount_inc_not_zero() under ls_lock, and cleared under ls_lock
before the final nfs4_put_stid() on the dispose path; the retry
path intentionally retains it. Remove the self-rearm
mod_delayed_work() at the top of the worker.
The Linux kernel CVE team has assigned CVE-2026-89681 to this issue.
Affected and fixed versions
===========================
Issue introduced in 7.1 with commit f52792f484ba2316853736856dde19b7e7458861 and fixed in 7.2.4 with commit a278d361e0e8f242211891193d56483a7a9f47a8
Issue introduced in 7.1 with commit f52792f484ba2316853736856dde19b7e7458861 and fixed in 7.3-rc1 with commit 8580571227451384399b3fa53fcde19848c48e5a
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-2026-89681
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/nfs4layouts.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/a278d361e0e8f242211891193d56483a7a9f47a8
https://git.kernel.org/stable/c/8580571227451384399b3fa53fcde19848c48e5a
reply other threads:[~2026-09-11 20:02 UTC|newest]
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