linux-kernel - Re: [RFC 2/2] ima: Fix detection of read/write violations on stacked filesystems

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Date: Tue, 16 Apr 2024 08:18:09 -0400
From: Mimi Zohar <zohar@...ux.ibm.com>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: Stefan Berger <stefanb@...ux.ibm.com>,
        Amir Goldstein
 <amir73il@...il.com>, linux-integrity@...r.kernel.org,
        linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        roberto.sassu@...wei.com, Christian Brauner <brauner@...nel.org>
Subject: Re: [RFC 2/2] ima: Fix detection of read/write violations on
 stacked filesystems

On Tue, 2024-04-16 at 10:05 +0200, Miklos Szeredi wrote:
> On Mon, 15 Apr 2024 at 20:35, Mimi Zohar <zohar@...ux.ibm.com> wrote:
> 
> > Although "Changes to the underlying filesystems while part of a mounted overlay
> > filesystem are not allowed.", from an integrity perspective these changes might
> > affect overlay files.  So they need to be detected and possibly re-measured, re-
> > appraised, and/or re-audited [1, 2].
> 
> How are changes of non-overlay files detected?

Originally there was a single measureent unless the filesystem was mounted with
SB_I_VERSION.  With commit a2a2c3c8580a ("ima: Use i_version only when
filesystem supports it") this changed to always re-measure the file if the
filesystem wasn't mounted with SB_I_VERSION.

With commit db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version")
it's not directly accessing i_version.

thanks,

Mimi