linux-cve-announce - CVE-2024-26678: x86/efistub: Use 1:1 file:memory mapping for PE/COFF .compat section

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Date: Tue,  2 Apr 2024 09:01:55 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-26678: x86/efistub: Use 1:1 file:memory mapping for PE/COFF .compat section

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

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

x86/efistub: Use 1:1 file:memory mapping for PE/COFF .compat section

The .compat section is a dummy PE section that contains the address of
the 32-bit entrypoint of the 64-bit kernel image if it is bootable from
32-bit firmware (i.e., CONFIG_EFI_MIXED=y)

This section is only 8 bytes in size and is only referenced from the
loader, and so it is placed at the end of the memory view of the image,
to avoid the need for padding it to 4k, which is required for sections
appearing in the middle of the image.

Unfortunately, this violates the PE/COFF spec, and even if most EFI
loaders will work correctly (including the Tianocore reference
implementation), PE loaders do exist that reject such images, on the
basis that both the file and memory views of the file contents should be
described by the section headers in a monotonically increasing manner
without leaving any gaps.

So reorganize the sections to avoid this issue. This results in a slight
padding overhead (< 4k) which can be avoided if desired by disabling
CONFIG_EFI_MIXED (which is only needed in rare cases these days)

The Linux kernel CVE team has assigned CVE-2024-26678 to this issue.

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

	Issue introduced in 6.7 with commit 3e3eabe26dc8 and fixed in 6.7.5 with commit 4adeeff8c123
	Issue introduced in 6.7 with commit 3e3eabe26dc8 and fixed in 6.8 with commit 1ad55cecf22f

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-2024-26678
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/boot/header.S
	arch/x86/boot/setup.ld

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/4adeeff8c12321cd453412a659c3c0eeb9bb2397
	https://git.kernel.org/stable/c/1ad55cecf22f05f1c884adf63cc09d3c3e609ebf