linux-cve-announce - CVE-2024-50191: ext4: don't set SB

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Message-ID: <2024110851-CVE-2024-50191-f31c@gregkh>
Date: Fri,  8 Nov 2024 06:43:54 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-50191: ext4: don't set SB_RDONLY after filesystem errors

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

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

ext4: don't set SB_RDONLY after filesystem errors

When the filesystem is mounted with errors=remount-ro, we were setting
SB_RDONLY flag to stop all filesystem modifications. We knew this misses
proper locking (sb->s_umount) and does not go through proper filesystem
remount procedure but it has been the way this worked since early ext2
days and it was good enough for catastrophic situation damage
mitigation. Recently, syzbot has found a way (see link) to trigger
warnings in filesystem freezing because the code got confused by
SB_RDONLY changing under its hands. Since these days we set
EXT4_FLAGS_SHUTDOWN on the superblock which is enough to stop all
filesystem modifications, modifying SB_RDONLY shouldn't be needed. So
stop doing that.

The Linux kernel CVE team has assigned CVE-2024-50191 to this issue.

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

	Fixed in 5.15.168 with commit fbb177bc1d64
	Fixed in 6.1.113 with commit 4061e07f040a
	Fixed in 6.6.57 with commit 58c0648e4c77
	Fixed in 6.11.4 with commit ee77c3884691
	Fixed in 6.12-rc1 with commit d3476f3dad4a

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-2024-50191
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/fbb177bc1d6487cd3e9b50ae0be2781b7297980d
	https://git.kernel.org/stable/c/4061e07f040a091f694f461b86a26cf95ae66439
	https://git.kernel.org/stable/c/58c0648e4c773f5b54f0cb63bc8c7c6bf52719a9
	https://git.kernel.org/stable/c/ee77c388469116565e009eaa704a60bc78489e09
	https://git.kernel.org/stable/c/d3476f3dad4ad68ae5f6b008ea6591d1520da5d8