linux-cve-announce - CVE-2023-54021: ext4: set goal start correctly in ext4_mb_normalize

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Message-ID: <2025122433-CVE-2023-54021-15bf@gregkh>
Date: Wed, 24 Dec 2025 11:57:05 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-54021: ext4: set goal start correctly in ext4_mb_normalize_request

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

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

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

ext4: set goal start correctly in ext4_mb_normalize_request

We need to set ac_g_ex to notify the goal start used in
ext4_mb_find_by_goal. Set ac_g_ex instead of ac_f_ex in
ext4_mb_normalize_request.
Besides we should assure goal start is in range [first_data_block,
blocks_count) as ext4_mb_initialize_context does.

[ Added a check to make sure size is less than ar->pright; otherwise
  we could end up passing an underflowed value of ar->pright - size to
  ext4_get_group_no_and_offset(), which will trigger a BUG_ON later on.
  - TYT ]

The Linux kernel CVE team has assigned CVE-2023-54021 to this issue.


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

	Fixed in 4.14.316 with commit 2479bb6cbdb4d56b807bbe5229e3e26a6f1f4530
	Fixed in 4.19.284 with commit 390eee955d4de4662db5e3e9e9a9eae020432cb7
	Fixed in 5.4.244 with commit cee78217a7ae72d11c2e21e1a5263b8044489823
	Fixed in 5.10.181 with commit 3ca3005b502ca8ea87d6a344323b179b48c4e4a3
	Fixed in 5.15.113 with commit bc4a3e1d07a86ae5845321d371190244acacb2f2
	Fixed in 6.1.30 with commit c6bee8970075b256fc1b07bf4873049219380818
	Fixed in 6.3.4 with commit abb330ffaa3a0ae7ce632e28c9260b461c01f19f
	Fixed in 6.4 with commit b07ffe6927c75d99af534d685282ea188d9f71a6

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-2023-54021
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:
	fs/ext4/mballoc.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/2479bb6cbdb4d56b807bbe5229e3e26a6f1f4530
	https://git.kernel.org/stable/c/390eee955d4de4662db5e3e9e9a9eae020432cb7
	https://git.kernel.org/stable/c/cee78217a7ae72d11c2e21e1a5263b8044489823
	https://git.kernel.org/stable/c/3ca3005b502ca8ea87d6a344323b179b48c4e4a3
	https://git.kernel.org/stable/c/bc4a3e1d07a86ae5845321d371190244acacb2f2
	https://git.kernel.org/stable/c/c6bee8970075b256fc1b07bf4873049219380818
	https://git.kernel.org/stable/c/abb330ffaa3a0ae7ce632e28c9260b461c01f19f
	https://git.kernel.org/stable/c/b07ffe6927c75d99af534d685282ea188d9f71a6