tree b44e6bd3db73721403c8c102b27d55c78cad8090
parent 6b7e661f9e9e48da93b6f8d233751ee9a73a09bb
author Ojaswin Mujoo <ojaswin@linux.ibm.com> 1732192734 +0530
committer Kevin Berry <kpberry@google.com> 1736710679 -0800

quota: flush quota_release_work upon quota writeback

[ Upstream commit ac6f420291b3fee1113f21d612fa88b628afab5b ]

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.

BUG=b/389044397
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2024-56780 in the Linux kernel.

cos-patch: security-moderate
Reported-by: Disha Goel <disgoel@linux.ibm.com>
CC: stable@vger.kernel.org
Fixes: dabc8b207566 ("quota: fix dqput() to follow the guarantees dquot_srcu should provide")
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Change-Id: I3afd1eadc5cfedf79c9d8a0da92771d8c1434eaa
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20241121123855.645335-2-ojaswin@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kernel CVE Triage Automation <cloud-image-kernel-cve-triage-automation@prod.google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/90262
Reviewed-by: Kevin Berry <kpberry@google.com>
Reviewed-by: Arnav Kansal <rnv@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>