linux-cve-announce - CVE-2022-49090: arch/arm64: Fix topology initialization for core scheduling

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Message-ID: <2025022658-CVE-2022-49090-c4ae@gregkh>
Date: Wed, 26 Feb 2025 02:54:55 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49090: arch/arm64: Fix topology initialization for core scheduling

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

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

arch/arm64: Fix topology initialization for core scheduling

Arm64 systems rely on store_cpu_topology() to call update_siblings_masks()
to transfer the toplogy to the various cpu masks. This needs to be done
before the call to notify_cpu_starting() which tells the scheduler about
each cpu found, otherwise the core scheduling data structures are setup
in a way that does not match the actual topology.

With smt_mask not setup correctly we bail on `cpumask_weight(smt_mask) == 1`
for !leaders in:

 notify_cpu_starting()
   cpuhp_invoke_callback_range()
     sched_cpu_starting()
       sched_core_cpu_starting()

which leads to rq->core not being correctly set for !leader-rq's.

Without this change stress-ng (which enables core scheduling in its prctl
tests in newer versions -- i.e. with PR_SCHED_CORE support) causes a warning
and then a crash (trimmed for legibility):

[ 1853.805168] ------------[ cut here ]------------
[ 1853.809784] task_rq(b)->core != rq->core
[ 1853.809792] WARNING: CPU: 117 PID: 0 at kernel/sched/fair.c:11102 cfs_prio_less+0x1b4/0x1c4
...
[ 1854.015210] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
...
[ 1854.231256] Call trace:
[ 1854.233689]  pick_next_task+0x3dc/0x81c
[ 1854.237512]  __schedule+0x10c/0x4cc
[ 1854.240988]  schedule_idle+0x34/0x54

The Linux kernel CVE team has assigned CVE-2022-49090 to this issue.


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

	Issue introduced in 5.14 with commit 9edeaea1bc452372718837ed2ba775811baf1ba1 and fixed in 5.15.34 with commit 87f5d66daa5f457449bb95d6b8d18bb7596aa627
	Issue introduced in 5.14 with commit 9edeaea1bc452372718837ed2ba775811baf1ba1 and fixed in 5.16.20 with commit 790c1567582bda8f1153015436e3330a7c6eb278
	Issue introduced in 5.14 with commit 9edeaea1bc452372718837ed2ba775811baf1ba1 and fixed in 5.17.3 with commit c78a1b2d0bff678570c8dc9f14035606f5e5257d
	Issue introduced in 5.14 with commit 9edeaea1bc452372718837ed2ba775811baf1ba1 and fixed in 5.18 with commit 5524cbb1bfcdff0cad0aaa9f94e6092002a07259

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-2022-49090
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/arm64/kernel/smp.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/87f5d66daa5f457449bb95d6b8d18bb7596aa627
	https://git.kernel.org/stable/c/790c1567582bda8f1153015436e3330a7c6eb278
	https://git.kernel.org/stable/c/c78a1b2d0bff678570c8dc9f14035606f5e5257d
	https://git.kernel.org/stable/c/5524cbb1bfcdff0cad0aaa9f94e6092002a07259