From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-90276: md/md-llbitmap: stop daemon timer rearm on destroy
Date: Thu, 17 Sep 2026 17:11:46 +0100 [thread overview]
Message-ID: <2026091749-CVE-2026-90276-fed2@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
md/md-llbitmap: stop daemon timer rearm on destroy
llbitmap_destroy() deletes pending_timer before flushing
md_llbitmap_io_wq. However, daemon_work can still be queued or running
after the timer has been deleted, and the daemon path can arm
pending_timer again when it finds dirty chunks that are not ready to
flush yet.
If that happens during teardown, pending_timer can remain armed after
llbitmap is freed and later dereference freed memory.
Add a BITMAP_SHUTDOWN bit to llbitmap->flags, set it before deleting
the timer, and make the timer and daemon paths stop queueing or rearming
work once teardown starts. Cancel daemon_work before flushing the shared
workqueue so no already queued daemon instance can race with the free.
Use timer_shutdown_sync() so a daemon instance that passed the shutdown
check before teardown cannot rearm the timer afterward.
BITMAP_SHUTDOWN is a runtime-only state. Mask it out when reading and
updating the llbitmap superblock so the shutdown state is never loaded
from disk or persisted to disk.
The Linux kernel CVE team has assigned CVE-2026-90276 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.18 with commit 5ab829f1971dc99f2aac10846c378e67fc875abc and fixed in 6.18.52 with commit c55aa6c17f019b6296952d336939891efa084c06
Issue introduced in 6.18 with commit 5ab829f1971dc99f2aac10846c378e67fc875abc and fixed in 7.2.6 with commit bb7f92d58fca9a9f06f3f51a82481c5f0bbbd46c
Issue introduced in 6.18 with commit 5ab829f1971dc99f2aac10846c378e67fc875abc and fixed in 7.3-rc1 with commit 5553d64e01d9a995be6c3de38501c6dd4ceede3b
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-2026-90276
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:
drivers/md/md-bitmap.h
drivers/md/md-llbitmap.c
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/c55aa6c17f019b6296952d336939891efa084c06
https://git.kernel.org/stable/c/bb7f92d58fca9a9f06f3f51a82481c5f0bbbd46c
https://git.kernel.org/stable/c/5553d64e01d9a995be6c3de38501c6dd4ceede3b
reply other threads:[~2026-09-17 16:23 UTC|newest]
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