linux-cve-announce - CVE-2022-50296: UM: cpuinfo: Fix a warning for CONFIG_CPUMASK

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Message-ID: <2025091557-CVE-2022-50296-7d7e@gregkh>
Date: Mon, 15 Sep 2025 16:45:58 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-50296: UM: cpuinfo: Fix a warning for CONFIG_CPUMASK_OFFSTACK

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

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

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

UM: cpuinfo: Fix a warning for CONFIG_CPUMASK_OFFSTACK

When CONFIG_CPUMASK_OFFSTACK and CONFIG_DEBUG_PER_CPU_MAPS is selected,
cpu_max_bits_warn() generates a runtime warning similar as below while
we show /proc/cpuinfo. Fix this by using nr_cpu_ids (the runtime limit)
instead of NR_CPUS to iterate CPUs.

[    3.052463] ------------[ cut here ]------------
[    3.059679] WARNING: CPU: 3 PID: 1 at include/linux/cpumask.h:108 show_cpuinfo+0x5e8/0x5f0
[    3.070072] Modules linked in: efivarfs autofs4
[    3.076257] CPU: 0 PID: 1 Comm: systemd Not tainted 5.19-rc5+ #1052
[    3.099465] Stack : 9000000100157b08 9000000000f18530 9000000000cf846c 9000000100154000
[    3.109127]         9000000100157a50 0000000000000000 9000000100157a58 9000000000ef7430
[    3.118774]         90000001001578e8 0000000000000040 0000000000000020 ffffffffffffffff
[    3.128412]         0000000000aaaaaa 1ab25f00eec96a37 900000010021de80 900000000101c890
[    3.138056]         0000000000000000 0000000000000000 0000000000000000 0000000000aaaaaa
[    3.147711]         ffff8000339dc220 0000000000000001 0000000006ab4000 0000000000000000
[    3.157364]         900000000101c998 0000000000000004 9000000000ef7430 0000000000000000
[    3.167012]         0000000000000009 000000000000006c 0000000000000000 0000000000000000
[    3.176641]         9000000000d3de08 9000000001639390 90000000002086d8 00007ffff0080286
[    3.186260]         00000000000000b0 0000000000000004 0000000000000000 0000000000071c1c
[    3.195868]         ...
[    3.199917] Call Trace:
[    3.203941] [<90000000002086d8>] show_stack+0x38/0x14c
[    3.210666] [<9000000000cf846c>] dump_stack_lvl+0x60/0x88
[    3.217625] [<900000000023d268>] __warn+0xd0/0x100
[    3.223958] [<9000000000cf3c90>] warn_slowpath_fmt+0x7c/0xcc
[    3.231150] [<9000000000210220>] show_cpuinfo+0x5e8/0x5f0
[    3.238080] [<90000000004f578c>] seq_read_iter+0x354/0x4b4
[    3.245098] [<90000000004c2e90>] new_sync_read+0x17c/0x1c4
[    3.252114] [<90000000004c5174>] vfs_read+0x138/0x1d0
[    3.258694] [<90000000004c55f8>] ksys_read+0x70/0x100
[    3.265265] [<9000000000cfde9c>] do_syscall+0x7c/0x94
[    3.271820] [<9000000000202fe4>] handle_syscall+0xc4/0x160
[    3.281824] ---[ end trace 8b484262b4b8c24c ]---

The Linux kernel CVE team has assigned CVE-2022-50296 to this issue.


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

	Fixed in 4.9.331 with commit 8f96aa67c2ccbd7e41b8dc992b8d13cfe206d571
	Fixed in 4.14.296 with commit dbd964a733db015bbb9dff592c259c736398140f
	Fixed in 4.19.262 with commit 844748412be03a236dcf4a208b588162a275e189
	Fixed in 5.4.220 with commit cd251d39b13485eb94ee65bb000d024e02c00e45
	Fixed in 5.10.150 with commit 6a73e6edcbf3cdd82796dcdf0c0f5fe5d91021af
	Fixed in 5.15.75 with commit 7efe61dc6aa45aab8a40e304fa2dae21e33b0db4
	Fixed in 5.19.17 with commit 5177bdc38eaa1c1ca6302214ab06913540cd00a2
	Fixed in 6.0.3 with commit 2e3863cc02c156b51b50592d43ffa6a13b680b0d
	Fixed in 6.1 with commit 16c546e148fa6d14a019431436a6f7b4087dbccd

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-2022-50296
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:
	arch/um/kernel/um_arch.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/8f96aa67c2ccbd7e41b8dc992b8d13cfe206d571
	https://git.kernel.org/stable/c/dbd964a733db015bbb9dff592c259c736398140f
	https://git.kernel.org/stable/c/844748412be03a236dcf4a208b588162a275e189
	https://git.kernel.org/stable/c/cd251d39b13485eb94ee65bb000d024e02c00e45
	https://git.kernel.org/stable/c/6a73e6edcbf3cdd82796dcdf0c0f5fe5d91021af
	https://git.kernel.org/stable/c/7efe61dc6aa45aab8a40e304fa2dae21e33b0db4
	https://git.kernel.org/stable/c/5177bdc38eaa1c1ca6302214ab06913540cd00a2
	https://git.kernel.org/stable/c/2e3863cc02c156b51b50592d43ffa6a13b680b0d
	https://git.kernel.org/stable/c/16c546e148fa6d14a019431436a6f7b4087dbccd