Re: [PATCH v6 0/3] ima: Detect changes to files via kstat changes rather than i_version

Frederick Lawler
2026-02-12T20:01:22Z

On Thu, Feb 12, 2026 at 02:45:58PM -0500, Mimi Zohar wrote:
> On Mon, 2026-02-09 at 15:21 -0600, Frederick Lawler wrote:
> > We uncovered a case in kernels >= 6.13 where XFS is no longer updating
> > struct kstat.change_cookie on i_op getattr() access calls. Instead, XFS is
> > using multigrain ctime (as well as other file systems) for
> > change detection in commit 1cf7e834a6fb ("xfs: switch to
> > multigrain timestamps").
> >
> > Because file systems may implement i_version as they see fit, IMA
> > unnecessarily measures files.
>
> Statements like this are wrong and certainly unnecessary. Refer to commit
> db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version"). Directly
> accessing the i_version still worked on local filesystems.

Sorry, that's the intention I was trying to get across.

>
> I'll be posting a patch shortly that falls back to directly reading the
> i_version, when STATX_CHANGE_COOKIE is not supported. It cleans up the file
> change detection code, making it more readable and should simplify adding the
> ctime file change detection.
>
> > We're proposing to compare against the kstat.change_cookie
> > directly to the cached version, and fall back to a ctime comparison,
> > if STATX_CHANGE_COOKIE is not supplied by vfs_getattr_nosec()'s result
> > mask.
>
> Please rebase your proposed change on this patch.
>

Sounds good. I'll keep an eye out for it.