linux-cve-announce - CVE-2022-49348: ext4: filter out EXT4_FC_REPLAY from on-disk superblock field s

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Message-ID: <2025022642-CVE-2022-49348-d5db@gregkh>
Date: Wed, 26 Feb 2025 03:10:22 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49348: ext4: filter out EXT4_FC_REPLAY from on-disk superblock field s_state

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

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

ext4: filter out EXT4_FC_REPLAY from on-disk superblock field s_state

The EXT4_FC_REPLAY bit in sbi->s_mount_state is used to indicate that
we are in the middle of replay the fast commit journal.  This was
actually a mistake, since the sbi->s_mount_info is initialized from
es->s_state.  Arguably s_mount_state is misleadingly named, but the
name is historical --- s_mount_state and s_state dates back to ext2.

What should have been used is the ext4_{set,clear,test}_mount_flag()
inline functions, which sets EXT4_MF_* bits in sbi->s_mount_flags.

The problem with using EXT4_FC_REPLAY is that a maliciously corrupted
superblock could result in EXT4_FC_REPLAY getting set in
s_mount_state.  This bypasses some sanity checks, and this can trigger
a BUG() in ext4_es_cache_extent().  As a easy-to-backport-fix, filter
out the EXT4_FC_REPLAY bit for now.  We should eventually transition
away from EXT4_FC_REPLAY to something like EXT4_MF_REPLAY.

The Linux kernel CVE team has assigned CVE-2022-49348 to this issue.

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

	Fixed in 5.10.121 with commit cc5b09cb6dacd4b32640537929ab4ee8fb2b9e04
	Fixed in 5.15.46 with commit b99fd73418350dea360da8311e87a6a7b0e15a4c
	Fixed in 5.17.14 with commit af2f1932743fb52ebcb008ad7ac500d9df0aa796
	Fixed in 5.18.3 with commit 55b4dbb29054a05d839562f6d635ce05669b016d
	Fixed in 5.19 with commit c878bea3c9d724ddfa05a813f30de3d25a0ba83f

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-2022-49348
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/super.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/cc5b09cb6dacd4b32640537929ab4ee8fb2b9e04
	https://git.kernel.org/stable/c/b99fd73418350dea360da8311e87a6a7b0e15a4c
	https://git.kernel.org/stable/c/af2f1932743fb52ebcb008ad7ac500d9df0aa796
	https://git.kernel.org/stable/c/55b4dbb29054a05d839562f6d635ce05669b016d
	https://git.kernel.org/stable/c/c878bea3c9d724ddfa05a813f30de3d25a0ba83f