linux-kernel - Re: [PATCH v2 0/3] Allow individual features to be locked down

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Message-ID: <7hmu5jbctmzdp75kipvjr3dzdmnkl4fpg3tkr4jcc5jcqzse6i@rpocehoxrjis>
Date: Thu, 14 Aug 2025 12:51:20 +0200
From: Nicolas Bouchinet <nicolas.bouchinet@....cyber.gouv.fr>
To: Nikolay Borisov <nik.borisov@...e.com>
Cc: linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org, 
	paul@...l-moore.com, serge@...lyn.com, jmorris@...ei.org, dan.j.williams@...el.com, 
	Xiujianfeng <xiujianfeng@...wei.com>
Subject: Re: [PATCH v2 0/3] Allow individual features to be locked down

On Thu, Aug 14, 2025 at 01:02:36PM +0300, Nikolay Borisov wrote:
> 
> 
> On 8/14/25 11:59, Nicolas Bouchinet wrote:
> > Hi Nikolay,
> > 
> > After discussing with Xiu, we have decided not to accept this patchset.
> > 
> > The goal of Lockdown being to draw a clear line between ring-0 and uid-0,
> > having a more granular way to activate Lockdown will break it. Primarily
> > because most lockdown-reasons can be bypassed if used independently.
> > 
> > Even if the goal of Lockdown were to be redefined, we would need to ensure the
> > security interdependence between different lockdown-reasons. This is highly
> > tied to where people calls the `security_locked_down` hook and thus is out of
> > our maintenance scope.
> > 
> > Having coarse-grained lockdown reasons and integrity/confidentiality levels
> > allows us to ensure that all of the reasons are correctly locked down.
> > 
> > Best regards,
> > 
> > Nicolas
> 
> Thanks for the feedback, to try and not have all this code go to waste, what
> about consdering patch 2 - kunits tests. Apart from
> lockdown_test_individual_level() the other tests are applicable to the
> existing lockdown implementation and can aid in future developments?
> 

Yes of course, thanks a lot for those tests. Can you adapt them and send
them separately for review ?

i.e, the `lockdown_test_no_downgrade` should check for -EPERM.

FYI, I have a three week holiday starting today. I'll return on
Septembre the 8th. I let Xiu review those patches until then.