linux-cve-announce - CVE-2022-50771: rcu: Fix __this_cpu_read() lockdep warning in rcu_force_quiescent

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Message-ID: <2025122458-CVE-2022-50771-3440@gregkh>
Date: Wed, 24 Dec 2025 14:06:22 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50771: rcu: Fix __this_cpu_read() lockdep warning in rcu_force_quiescent_state()

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

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

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

rcu: Fix __this_cpu_read() lockdep warning in rcu_force_quiescent_state()

Running rcutorture with non-zero fqs_duration module parameter in a
kernel built with CONFIG_PREEMPTION=y results in the following splat:

BUG: using __this_cpu_read() in preemptible [00000000]
code: rcu_torture_fqs/398
caller is __this_cpu_preempt_check+0x13/0x20
CPU: 3 PID: 398 Comm: rcu_torture_fqs Not tainted 6.0.0-rc1-yoctodev-standard+
Call Trace:
<TASK>
dump_stack_lvl+0x5b/0x86
dump_stack+0x10/0x16
check_preemption_disabled+0xe5/0xf0
__this_cpu_preempt_check+0x13/0x20
rcu_force_quiescent_state.part.0+0x1c/0x170
rcu_force_quiescent_state+0x1e/0x30
rcu_torture_fqs+0xca/0x160
? rcu_torture_boost+0x430/0x430
kthread+0x192/0x1d0
? kthread_complete_and_exit+0x30/0x30
ret_from_fork+0x22/0x30
</TASK>

The problem is that rcu_force_quiescent_state() uses __this_cpu_read()
in preemptible code instead of the proper raw_cpu_read().  This commit
therefore changes __this_cpu_read() to raw_cpu_read().

The Linux kernel CVE team has assigned CVE-2022-50771 to this issue.

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

	Fixed in 5.4.229 with commit 3d92527a919edd1aa381bdd6c299dd75a8167396
	Fixed in 5.10.163 with commit 5a52380b8193cf8be6c4a6b94b86ef64ed80c0dc
	Fixed in 5.15.86 with commit 98a5b1265a36e9d843a51ddd6c9fa02da50d2c57
	Fixed in 6.0.16 with commit a74af9b937707b42c3fd041aae1ed4ce2f337307
	Fixed in 6.1.2 with commit 80a3e7ab477b3655615fc1627c88c248d4ad28d9
	Fixed in 6.2 with commit ceb1c8c9b8aa9199da46a0f29d2d5f08d9b44c15

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-2022-50771
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/tree.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/3d92527a919edd1aa381bdd6c299dd75a8167396
	https://git.kernel.org/stable/c/5a52380b8193cf8be6c4a6b94b86ef64ed80c0dc
	https://git.kernel.org/stable/c/98a5b1265a36e9d843a51ddd6c9fa02da50d2c57
	https://git.kernel.org/stable/c/a74af9b937707b42c3fd041aae1ed4ce2f337307
	https://git.kernel.org/stable/c/80a3e7ab477b3655615fc1627c88c248d4ad28d9
	https://git.kernel.org/stable/c/ceb1c8c9b8aa9199da46a0f29d2d5f08d9b44c15