CVE-2024-56780 Information

Jan 09, 2025 cve

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.

Reference

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

Share on: