linux-cve-announce - CVE-2025-21811: nilfs2: protect access to buffers with no active references

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Message-ID: <2025022754-CVE-2025-21811-beb7@gregkh>
Date: Thu, 27 Feb 2025 12:00:05 -0800
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21811: nilfs2: protect access to buffers with no active references

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

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

nilfs2: protect access to buffers with no active references

nilfs_lookup_dirty_data_buffers(), which iterates through the buffers
attached to dirty data folios/pages, accesses the attached buffers without
locking the folios/pages.

For data cache, nilfs_clear_folio_dirty() may be called asynchronously
when the file system degenerates to read only, so
nilfs_lookup_dirty_data_buffers() still has the potential to cause use
after free issues when buffers lose the protection of their dirty state
midway due to this asynchronous clearing and are unintentionally freed by
try_to_free_buffers().

Eliminate this race issue by adjusting the lock section in this function.

The Linux kernel CVE team has assigned CVE-2025-21811 to this issue.


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

	Issue introduced in 3.10 with commit 8c26c4e2694a163d525976e804d81cd955bbb40c and fixed in 6.1.129 with commit 58c27fa7a610b6e8d44e6220e7dbddfbaccaf439
	Issue introduced in 3.10 with commit 8c26c4e2694a163d525976e804d81cd955bbb40c and fixed in 6.6.76 with commit 8e1b9201c9a24638cf09c6e1c9f224157328010b
	Issue introduced in 3.10 with commit 8c26c4e2694a163d525976e804d81cd955bbb40c and fixed in 6.12.13 with commit 4b08d23d7d1917bef4fbee8ad81372f49b006656
	Issue introduced in 3.10 with commit 8c26c4e2694a163d525976e804d81cd955bbb40c and fixed in 6.13.2 with commit c437dfac9f7a5a46ac2a5e6d6acd3059e9f68188
	Issue introduced in 3.10 with commit 8c26c4e2694a163d525976e804d81cd955bbb40c and fixed in 6.14-rc1 with commit 367a9bffabe08c04f6d725032cce3d891b2b9e1a

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-2025-21811
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/nilfs2/segment.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/58c27fa7a610b6e8d44e6220e7dbddfbaccaf439
	https://git.kernel.org/stable/c/8e1b9201c9a24638cf09c6e1c9f224157328010b
	https://git.kernel.org/stable/c/4b08d23d7d1917bef4fbee8ad81372f49b006656
	https://git.kernel.org/stable/c/c437dfac9f7a5a46ac2a5e6d6acd3059e9f68188
	https://git.kernel.org/stable/c/367a9bffabe08c04f6d725032cce3d891b2b9e1a