linux-cve-announce - CVE-2025-23132: f2fs: quota: fix to avoid warning in dquot_writeback

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Message-ID: <2025041631-CVE-2025-23132-cbf9@gregkh>
Date: Wed, 16 Apr 2025 16:13:43 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-23132: f2fs: quota: fix to avoid warning in dquot_writeback_dquots()

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

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

f2fs: quota: fix to avoid warning in dquot_writeback_dquots()

F2FS-fs (dm-59): checkpoint=enable has some unwritten data.

------------[ cut here ]------------
WARNING: CPU: 6 PID: 8013 at fs/quota/dquot.c:691 dquot_writeback_dquots+0x2fc/0x308
pc : dquot_writeback_dquots+0x2fc/0x308
lr : f2fs_quota_sync+0xcc/0x1c4
Call trace:
dquot_writeback_dquots+0x2fc/0x308
f2fs_quota_sync+0xcc/0x1c4
f2fs_write_checkpoint+0x3d4/0x9b0
f2fs_issue_checkpoint+0x1bc/0x2c0
f2fs_sync_fs+0x54/0x150
f2fs_do_sync_file+0x2f8/0x814
__f2fs_ioctl+0x1960/0x3244
f2fs_ioctl+0x54/0xe0
__arm64_sys_ioctl+0xa8/0xe4
invoke_syscall+0x58/0x114

checkpoint and f2fs_remount may race as below, resulting triggering warning
in dquot_writeback_dquots().

atomic write                                    remount
                                                - do_remount
                                                 - down_write(&sb->s_umount);
                                                  - f2fs_remount
- ioctl
 - f2fs_do_sync_file
  - f2fs_sync_fs
   - f2fs_write_checkpoint
    - block_operations
     - locked = down_read_trylock(&sbi->sb->s_umount)
       : fail to lock due to the write lock was held by remount
                                                 - up_write(&sb->s_umount);
     - f2fs_quota_sync
      - dquot_writeback_dquots
       - WARN_ON_ONCE(!rwsem_is_locked(&sb->s_umount))
       : trigger warning because s_umount lock was unlocked by remount

If checkpoint comes from mount/umount/remount/freeze/quotactl, caller of
checkpoint has already held s_umount lock, calling dquot_writeback_dquots()
in the context should be safe.

So let's record task to sbi->umount_lock_holder, so that checkpoint can
know whether the lock has held in the context or not by checking current
w/ it.

In addition, in order to not misrepresent caller of checkpoint, we should
not allow to trigger async checkpoint for those callers: mount/umount/remount/
freeze/quotactl.

The Linux kernel CVE team has assigned CVE-2025-23132 to this issue.


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

	Issue introduced in 4.20 with commit af033b2aa8a874fd5737fafe90d159136527b5b4 and fixed in 6.14.2 with commit d7acf0a6c87aa282c86a36dbaa2f92fda88c5884
	Issue introduced in 4.20 with commit af033b2aa8a874fd5737fafe90d159136527b5b4 and fixed in 6.15-rc1 with commit eb85c2410d6f581e957cd03a644ff6ddbe592af9

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-2025-23132
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/f2fs/checkpoint.c
	fs/f2fs/f2fs.h
	fs/f2fs/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/d7acf0a6c87aa282c86a36dbaa2f92fda88c5884
	https://git.kernel.org/stable/c/eb85c2410d6f581e957cd03a644ff6ddbe592af9