linux-cve-announce - CVE-2023-54246: rcuscale: Move rcu_scale_writer() schedule_timeout_uninterruptible() to

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Message-ID: <2025123052-CVE-2023-54246-8abc@gregkh>
Date: Tue, 30 Dec 2025 13:20:12 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-54246: rcuscale: Move rcu_scale_writer() schedule_timeout_uninterruptible() to _idle()

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

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

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

rcuscale: Move rcu_scale_writer() schedule_timeout_uninterruptible() to _idle()

The rcuscale.holdoff module parameter can be used to delay the start
of rcu_scale_writer() kthread.  However, the hung-task timeout will
trigger when the timeout specified by rcuscale.holdoff is greater than
hung_task_timeout_secs:

runqemu kvm nographic slirp qemuparams="-smp 4 -m 2048M"
bootparams="rcuscale.shutdown=0 rcuscale.holdoff=300"

[  247.071753] INFO: task rcu_scale_write:59 blocked for more than 122 seconds.
[  247.072529]       Not tainted 6.4.0-rc1-00134-gb9ed6de8d4ff #7
[  247.073400] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  247.074331] task:rcu_scale_write state:D stack:30144 pid:59    ppid:2      flags:0x00004000
[  247.075346] Call Trace:
[  247.075660]  <TASK>
[  247.075965]  __schedule+0x635/0x1280
[  247.076448]  ? __pfx___schedule+0x10/0x10
[  247.076967]  ? schedule_timeout+0x2dc/0x4d0
[  247.077471]  ? __pfx_lock_release+0x10/0x10
[  247.078018]  ? enqueue_timer+0xe2/0x220
[  247.078522]  schedule+0x84/0x120
[  247.078957]  schedule_timeout+0x2e1/0x4d0
[  247.079447]  ? __pfx_schedule_timeout+0x10/0x10
[  247.080032]  ? __pfx_rcu_scale_writer+0x10/0x10
[  247.080591]  ? __pfx_process_timeout+0x10/0x10
[  247.081163]  ? __pfx_sched_set_fifo_low+0x10/0x10
[  247.081760]  ? __pfx_rcu_scale_writer+0x10/0x10
[  247.082287]  rcu_scale_writer+0x6b1/0x7f0
[  247.082773]  ? mark_held_locks+0x29/0xa0
[  247.083252]  ? __pfx_rcu_scale_writer+0x10/0x10
[  247.083865]  ? __pfx_rcu_scale_writer+0x10/0x10
[  247.084412]  kthread+0x179/0x1c0
[  247.084759]  ? __pfx_kthread+0x10/0x10
[  247.085098]  ret_from_fork+0x2c/0x50
[  247.085433]  </TASK>

This commit therefore replaces schedule_timeout_uninterruptible() with
schedule_timeout_idle().

The Linux kernel CVE team has assigned CVE-2023-54246 to this issue.


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

	Fixed in 5.10.197 with commit 55887adc76e19aec9763186e2c1d0a3481d20e96
	Fixed in 5.15.133 with commit 4f03fba096bfded90e0d71eba8839a46922164d1
	Fixed in 6.1.55 with commit 83ed0cdb6ae0383dd14b02375c353773836884ed
	Fixed in 6.5.5 with commit 9416dccb31fdb190d25d57e97674f232651f6560
	Fixed in 6.6 with commit e60c122a1614b4f65b29a7bef9d83b9fd30e937a

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-2023-54246
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:
	kernel/rcu/rcuscale.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/55887adc76e19aec9763186e2c1d0a3481d20e96
	https://git.kernel.org/stable/c/4f03fba096bfded90e0d71eba8839a46922164d1
	https://git.kernel.org/stable/c/83ed0cdb6ae0383dd14b02375c353773836884ed
	https://git.kernel.org/stable/c/9416dccb31fdb190d25d57e97674f232651f6560
	https://git.kernel.org/stable/c/e60c122a1614b4f65b29a7bef9d83b9fd30e937a