linux-cve-announce - CVE-2022-49726: clocksource: hyper-v: unexport __init-annotated hv_init

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Message-ID: <2025022633-CVE-2022-49726-582f@gregkh>
Date: Wed, 26 Feb 2025 03:24:49 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49726: clocksource: hyper-v: unexport __init-annotated hv_init_clocksource()

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

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

clocksource: hyper-v: unexport __init-annotated hv_init_clocksource()

EXPORT_SYMBOL and __init is a bad combination because the .init.text
section is freed up after the initialization. Hence, modules cannot
use symbols annotated __init. The access to a freed symbol may end up
with kernel panic.

modpost used to detect it, but it has been broken for a decade.

Recently, I fixed modpost so it started to warn it again, then this
showed up in linux-next builds.

There are two ways to fix it:

  - Remove __init
  - Remove EXPORT_SYMBOL

I chose the latter for this case because the only in-tree call-site,
arch/x86/kernel/cpu/mshyperv.c is never compiled as modular.
(CONFIG_HYPERVISOR_GUEST is boolean)

The Linux kernel CVE team has assigned CVE-2022-49726 to this issue.


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

	Issue introduced in 5.3 with commit dd2cb348613b44f9d948b068775e159aad298599 and fixed in 5.4.200 with commit cff3a7ce6e81418b6e8bac941779bbf5d342d626
	Issue introduced in 5.3 with commit dd2cb348613b44f9d948b068775e159aad298599 and fixed in 5.10.124 with commit db965e2757d95f695e606856418cd84003dd036d
	Issue introduced in 5.3 with commit dd2cb348613b44f9d948b068775e159aad298599 and fixed in 5.15.49 with commit 0414eab7c78f3518143d383e448d44fc573ac6d2
	Issue introduced in 5.3 with commit dd2cb348613b44f9d948b068775e159aad298599 and fixed in 5.18.6 with commit 937fcbb55a1e48a6422e87e8f49422c92265f102
	Issue introduced in 5.3 with commit dd2cb348613b44f9d948b068775e159aad298599 and fixed in 5.19 with commit 245b993d8f6c4e25f19191edfbd8080b645e12b1

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-2022-49726
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/clocksource/hyperv_timer.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/cff3a7ce6e81418b6e8bac941779bbf5d342d626
	https://git.kernel.org/stable/c/db965e2757d95f695e606856418cd84003dd036d
	https://git.kernel.org/stable/c/0414eab7c78f3518143d383e448d44fc573ac6d2
	https://git.kernel.org/stable/c/937fcbb55a1e48a6422e87e8f49422c92265f102
	https://git.kernel.org/stable/c/245b993d8f6c4e25f19191edfbd8080b645e12b1