linux-cve-announce - CVE-2024-40917: memblock: make memblock_set_node() also warn about use of MAX

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Message-ID: <2024071211-CVE-2024-40917-0a05@gregkh>
Date: Fri, 12 Jul 2024 14:27:15 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-40917: memblock: make memblock_set_node() also warn about use of MAX_NUMNODES

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

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

memblock: make memblock_set_node() also warn about use of MAX_NUMNODES

On an (old) x86 system with SRAT just covering space above 4Gb:

    ACPI: SRAT: Node 0 PXM 0 [mem 0x100000000-0xfffffffff] hotplug

the commit referenced below leads to this NUMA configuration no longer
being refused by a CONFIG_NUMA=y kernel (previously

    NUMA: nodes only cover 6144MB of your 8185MB e820 RAM. Not used.
    No NUMA configuration found
    Faking a node at [mem 0x0000000000000000-0x000000027fffffff]

was seen in the log directly after the message quoted above), because of
memblock_validate_numa_coverage() checking for NUMA_NO_NODE (only). This
in turn led to memblock_alloc_range_nid()'s warning about MAX_NUMNODES
triggering, followed by a NULL deref in memmap_init() when trying to
access node 64's (NODE_SHIFT=6) node data.

To compensate said change, make memblock_set_node() warn on and adjust
a passed in value of MAX_NUMNODES, just like various other functions
already do.

The Linux kernel CVE team has assigned CVE-2024-40917 to this issue.


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

	Issue introduced in 6.8 with commit ff6c3d81f2e8 and fixed in 6.9.6 with commit 22f742b8f738
	Issue introduced in 6.8 with commit ff6c3d81f2e8 and fixed in 6.10-rc4 with commit e0eec24e2e19

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-2024-40917
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:
	mm/memblock.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/22f742b8f738918f683198a18ec3c691acda14c4
	https://git.kernel.org/stable/c/e0eec24e2e199873f43df99ec39773ad3af2bff7