linux-kernel - Re: [PATCH] ima: don't clear IMA_DIGSIG flag when setting non-IMA xattr

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Message-ID: <9fb8781bfb9c9ae9dd0a1413e23cae20dcd7356a.camel@linux.ibm.com>
Date: Mon, 08 Sep 2025 16:58:05 -0400
From: Mimi Zohar <zohar@...ux.ibm.com>
To: Coiby Xu <coxu@...hat.com>
Cc: linux-integrity@...r.kernel.org, Roberto Sassu
 <roberto.sassu@...wei.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        Eric Snowberg <eric.snowberg@...cle.com>,
        Paul Moore	
 <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn"	
 <serge@...lyn.com>,
        "open list:SECURITY SUBSYSTEM"	
 <linux-security-module@...r.kernel.org>,
        open list	
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ima: don't clear IMA_DIGSIG flag when setting non-IMA
 xattr

On Mon, 2025-09-08 at 10:53 -0400, Mimi Zohar wrote:
> Hi Coiby,
> 
> On Mon, 2025-09-08 at 19:12 +0800, Coiby Xu wrote:
> > > 
> > > Even without an IMA appraise policy, the security xattrs are written out to the
> > > filesystem, but the IMA_DIGSIG flag is not cached.
> > 
> > It seems I miss some context for the above sentence. If no IMA policy is
> > configured, no ima_iint_cache will be created. If you mean non-appraisal
> > policy, will not caching IMA_DIGSIG flag cause any problem?
> 
> Sorry.  What I was trying to say is that your test program illustrates the
> problem both with or without any of the boot command line options as you
> suggested - "ima_appraise=fix evm=fix ima_policy=appraise_tcb".  Writing some
> other security xattr is a generic problem, whether the file is in policy or not,
> whether IMA or EVM are in fix mode or not.  The rpm-plugin-ima should install
> the IMA signature regardless.

My mistake.  An appraise policy indeed needs to be defined for the file
signature to be replaced with a file hash.

> 
> SELinux doesn't usually re-write the security.selinux xattr, so the problem is
> hard to reproduce after installing the rpm-plugin-ima with "dnf reinstall
> <package>".
> 
> thanks,
> 
> Mimi
>