CVE-2024-56780: quota: flush quota_release_work upon quota writeback

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-01-08 · updated 2026-10-15

Description

In the Linux kernel, the following vulnerability has been resolved: quota: flush quota_release_work upon quota writeback One of the paths quota writeback is called from is: freeze_super() sync_filesystem() ext4_sync_fs() dquot_writeback_dquots() Since we currently don't always flush the quota_release_work queue in this path, we can end up with the following race: 1. dquot are added to releasing_dquots list during regular operations. 2. FS Freeze starts, however, this does not flush the quota_release_work queue. 3. Freeze completes. 4. Kernel eventually tries to flush the workqueue while FS is frozen which hits a WARN_ON since transaction gets started during frozen state: ext4_journal_check_start+0x28/0x110 [ext4] (unreliable) __ext4_journal_start_sb+0x64/0x1c0 [ext4] ext4_release_dquot+0x90/0x1d0 [ext4] quota_release_workfn+0x43c/0x4d0 Which is the following line: WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE); Which ultimately results in generic/390 failing due to dmesg noise. This was detected on powerpc machine 15 cores. To avoid this, make sure to flush the workqueue during dquot_writeback_dquots() so we dont have any pending workitems after freeze.

Affected products

Linux kernel: from 4.19.295 before 4.20; from 5.4.257 before 5.4.287; from 5.10.195 before 5.10.231; from 5.15.132 before 5.15.174; from 6.1.53 before 6.1.120; from 6.4.16 before 6.5 — fixed in 4.20, 5.10.231, 5.15.174, 5.4.287, 6.1.120, 6.12.4

How to fix

Upgrade to a fixed version: Linux kernel 4.20, 5.10.231, 5.15.174, 5.4.287. Check the vendor advisory for mitigations.

References

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