CVE-2025-23132

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.

This vulnerability is rated as Moderate because exploitation requires local access and specific concurrent filesystem operations on an active f2fs mount, limiting the attack surface. In standard Red Hat Enterprise Linux environments, f2fs is not configured as a default filesystem and requires explicit mounting. A local user capable of triggering simultaneous filesystem checkpoint syncs and remounts could induce kernel warnings and denial of service through kernel instability, without affecting confidentiality or integrity.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.