linux-cve-announce - CVE-2023-53496: x86/platform/uv: Use alternate source for socket to node data

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Message-ID: <2025100125-CVE-2023-53496-b145@gregkh>
Date: Wed,  1 Oct 2025 13:45:48 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53496: x86/platform/uv: Use alternate source for socket to node data

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

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

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

x86/platform/uv: Use alternate source for socket to node data

The UV code attempts to build a set of tables to allow it to do
bidirectional socket<=>node lookups.

But when nr_cpus is set to a smaller number than actually present, the
cpu_to_node() mapping information for unused CPUs is not available to
build_socket_tables(). This results in skipping some nodes or sockets
when creating the tables and leaving some -1's for later code to trip.
over, causing oopses.

The problem is that the socket<=>node lookups are created by doing a
loop over all CPUs, then looking up the CPU's APICID and socket. But
if a CPU is not present, there is no way to start this lookup.

Instead of looping over all CPUs, take CPUs out of the equation
entirely. Loop over all APICIDs which are mapped to a valid NUMA node.
Then just extract the socket-id from the APICID.

This avoid tripping over disabled CPUs.

The Linux kernel CVE team has assigned CVE-2023-53496 to this issue.

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

	Issue introduced in 6.5 with commit 8a50c58519271dd24ba760bb282875f6ad66ee71 and fixed in 6.5.5 with commit 0d01a0c3046d1545391ef7bb1f114743d00e3793
	Issue introduced in 6.5 with commit 8a50c58519271dd24ba760bb282875f6ad66ee71 and fixed in 6.6 with commit 5290e88ba2c742ca77c5f5b690e5af549cfd8591

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-2023-53496
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/x86/kernel/apic/x2apic_uv_x.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/0d01a0c3046d1545391ef7bb1f114743d00e3793
	https://git.kernel.org/stable/c/5290e88ba2c742ca77c5f5b690e5af549cfd8591