linux-kernel - xfs/ima: Regression caching i

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Message-ID: <aTspr4_h9IU4EyrR@CMGLRV3>
Date: Thu, 11 Dec 2025 14:29:35 -0600
From: Frederick Lawler <fred@...udflare.com>
To: Jeff Layton <jlayton@...nel.org>
Cc: Christian Brauner <brauner@...nel.org>,
	"Darrick J. Wong" <djwong@...nel.org>,
	Josef Bacik <josef@...icpanda.com>,
	Carlos Maiolino <cem@...nel.org>, linux-xfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org,
	linux-integrity@...r.kernel.org,
	Roberto Sassu <roberto.sassu@...wei.com>,
	kernel-team@...udflare.com
Subject: xfs/ima: Regression caching i_version

Hi Jeff,

While testing 6.18, I think I found a regression with
commit 1cf7e834a6fb ("xfs: switch to multigrain timestamps") since 6.13
where IMA is no longer able to properly cache i_version when we overlay
tmpfs on top of XFS. Each measurement diff check in function
process_measurement() reports that the i_version is
always set to zero for iint->real_inode.version.

The function ima_collect_measurement() is looking to extract the version
from the cookie on next measurement to cache i_version.

I'm unclear from the commit description what the right approach here is:
update in IMA land by checking for time changes, or do
something else such as adding the cookie back.

Thanks,
Fred