linux-cve-announce - CVE-2023-54316: refscale: Fix uninitalized use of wait_queue_head

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Message-ID: <2025123037-CVE-2023-54316-f3c8@gregkh>
Date: Tue, 30 Dec 2025 13:24:09 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-54316: refscale: Fix uninitalized use of wait_queue_head_t

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

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

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

refscale: Fix uninitalized use of wait_queue_head_t

Running the refscale test occasionally crashes the kernel with the
following error:

[ 8569.952896] BUG: unable to handle page fault for address: ffffffffffffffe8
[ 8569.952900] #PF: supervisor read access in kernel mode
[ 8569.952902] #PF: error_code(0x0000) - not-present page
[ 8569.952904] PGD c4b048067 P4D c4b049067 PUD c4b04b067 PMD 0
[ 8569.952910] Oops: 0000 [#1] PREEMPT_RT SMP NOPTI
[ 8569.952916] Hardware name: Dell Inc. PowerEdge R750/0WMWCR, BIOS 1.2.4 05/28/2021
[ 8569.952917] RIP: 0010:prepare_to_wait_event+0x101/0x190
  :
[ 8569.952940] Call Trace:
[ 8569.952941]  <TASK>
[ 8569.952944]  ref_scale_reader+0x380/0x4a0 [refscale]
[ 8569.952959]  kthread+0x10e/0x130
[ 8569.952966]  ret_from_fork+0x1f/0x30
[ 8569.952973]  </TASK>

The likely cause is that init_waitqueue_head() is called after the call to
the torture_create_kthread() function that creates the ref_scale_reader
kthread.  Although this init_waitqueue_head() call will very likely
complete before this kthread is created and starts running, it is
possible that the calling kthread will be delayed between the calls to
torture_create_kthread() and init_waitqueue_head().  In this case, the
new kthread will use the waitqueue head before it is properly initialized,
which is not good for the kernel's health and well-being.

The above crash happened here:

	static inline void __add_wait_queue(...)
	{
		:
		if (!(wq->flags & WQ_FLAG_PRIORITY)) <=== Crash here

The offset of flags from list_head entry in wait_queue_entry is
-0x18. If reader_tasks[i].wq.head.next is NULL as allocated reader_task
structure is zero initialized, the instruction will try to access address
0xffffffffffffffe8, which is exactly the fault address listed above.

This commit therefore invokes init_waitqueue_head() before creating
the kthread.

The Linux kernel CVE team has assigned CVE-2023-54316 to this issue.


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

	Issue introduced in 5.9 with commit 653ed64b01dc5989f8f579d0038e987476c2c023 and fixed in 5.10.195 with commit 066fbd8bc981cf49923bf828b7b4092894df577f
	Issue introduced in 5.9 with commit 653ed64b01dc5989f8f579d0038e987476c2c023 and fixed in 5.15.132 with commit ec9d118ad99dc6f1bc674c1e649c25533d89b9ba
	Issue introduced in 5.9 with commit 653ed64b01dc5989f8f579d0038e987476c2c023 and fixed in 6.1.53 with commit e0322a255a2242dbe4686b6176b3c83dea490529
	Issue introduced in 5.9 with commit 653ed64b01dc5989f8f579d0038e987476c2c023 and fixed in 6.4.16 with commit e5de968a9032366198720eac4f368ed7e690b3ef
	Issue introduced in 5.9 with commit 653ed64b01dc5989f8f579d0038e987476c2c023 and fixed in 6.5.3 with commit 70a2856fd1d0a040c876ba9e3f89b949ae92e4dd
	Issue introduced in 5.9 with commit 653ed64b01dc5989f8f579d0038e987476c2c023 and fixed in 6.6 with commit f5063e8948dad7f31adb007284a5d5038ae31bb8

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-2023-54316
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/refscale.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/066fbd8bc981cf49923bf828b7b4092894df577f
	https://git.kernel.org/stable/c/ec9d118ad99dc6f1bc674c1e649c25533d89b9ba
	https://git.kernel.org/stable/c/e0322a255a2242dbe4686b6176b3c83dea490529
	https://git.kernel.org/stable/c/e5de968a9032366198720eac4f368ed7e690b3ef
	https://git.kernel.org/stable/c/70a2856fd1d0a040c876ba9e3f89b949ae92e4dd
	https://git.kernel.org/stable/c/f5063e8948dad7f31adb007284a5d5038ae31bb8