linux-cve-announce - CVE-2023-53149: ext4: avoid deadlock in fs reclaim with page writeback

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Message-ID: <2025091552-CVE-2023-53149-2f0a@gregkh>
Date: Mon, 15 Sep 2025 16:02:12 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53149: ext4: avoid deadlock in fs reclaim with page writeback

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

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

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

ext4: avoid deadlock in fs reclaim with page writeback

Ext4 has a filesystem wide lock protecting ext4_writepages() calls to
avoid races with switching of journalled data flag or inode format. This
lock can however cause a deadlock like:

CPU0                            CPU1

ext4_writepages()
  percpu_down_read(sbi->s_writepages_rwsem);
                                ext4_change_inode_journal_flag()
                                  percpu_down_write(sbi->s_writepages_rwsem);
                                    - blocks, all readers block from now on
  ext4_do_writepages()
    ext4_init_io_end()
      kmem_cache_zalloc(io_end_cachep, GFP_KERNEL)
        fs_reclaim frees dentry...
          dentry_unlink_inode()
            iput() - last ref =>
              iput_final() - inode dirty =>
                write_inode_now()...
                  ext4_writepages() tries to acquire sbi->s_writepages_rwsem
                    and blocks forever

Make sure we cannot recurse into filesystem reclaim from writeback code
to avoid the deadlock.

The Linux kernel CVE team has assigned CVE-2023-53149 to this issue.


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

	Issue introduced in 4.7 with commit c8585c6fcaf2011de54c3592e80a634a2b9e1a7f and fixed in 6.2.16 with commit 2ec97dc90df40c50e509809dc9a198638a7e18b6
	Issue introduced in 4.7 with commit c8585c6fcaf2011de54c3592e80a634a2b9e1a7f and fixed in 6.3.3 with commit 4b4340bf04ce9a52061f15000ecedd126abc093c
	Issue introduced in 4.7 with commit c8585c6fcaf2011de54c3592e80a634a2b9e1a7f and fixed in 6.4 with commit 00d873c17e29cc32d90ca852b82685f1673acaa5

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-2023-53149
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/ext4.h
	fs/ext4/inode.c
	fs/ext4/migrate.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/2ec97dc90df40c50e509809dc9a198638a7e18b6
	https://git.kernel.org/stable/c/4b4340bf04ce9a52061f15000ecedd126abc093c
	https://git.kernel.org/stable/c/00d873c17e29cc32d90ca852b82685f1673acaa5