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.

Classification

CVE ID: CVE-2024-56780

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 5.07% (scored less or equal to compared to others)

EPSS Date: 2025-02-06 (when was this score calculated)

References

https://git.kernel.org/stable/c/a5abba5e0e586e258ded3e798fe5f69c66fec198
https://git.kernel.org/stable/c/6f3821acd7c3143145999248087de5fb4b48cf26
https://git.kernel.org/stable/c/ab6cfcf8ed2c7496f55d020b65b1d8cd55d9a2cb
https://git.kernel.org/stable/c/3e6ff207cd5bd924ad94cd1a7c633bcdac0ba1cb
https://git.kernel.org/stable/c/bcacb52a985f1b6d280f698a470b873dfe52728a
https://git.kernel.org/stable/c/8ea87e34792258825d290f4dc5216276e91cb224
https://git.kernel.org/stable/c/ac6f420291b3fee1113f21d612fa88b628afab5b

Timeline