Re: [PATCH v3 1/1] security: Add CONFIG_LSM_AUTO to handle default LSM stack ordering

From: "Mickaël Salaün" <mic@digikod.net>
To: Paul Moore <paul@paul-moore.com>, Kees Cook <keescook@chromium.org>
Cc: "Casey Schaufler" <casey@schaufler-ca.com>,
	"Nicolas Iooss" <nicolas.iooss@m4x.org>,
	"James Morris" <jmorris@namei.org>,
	"Serge E . Hallyn" <serge@hallyn.com>,
	linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	"Mickaël Salaün" <mic@linux.microsoft.com>
Subject: Re: [PATCH v3 1/1] security: Add CONFIG_LSM_AUTO to handle default LSM stack ordering
Date: Fri, 4 Nov 2022 17:29:15 +0100	[thread overview]
Message-ID: <c7808c82-621e-c20d-bff3-03a66df5528a@digikod.net> (raw)
In-Reply-To: <CAHC9VhSMLjzxyu0F82NZoea-q4yMgHeCZ0-TRcvxKks4WeKacQ@mail.gmail.com>

On 18/10/2022 21:31, Paul Moore wrote:
> On Tue, Oct 18, 2022 at 1:55 AM Kees Cook <keescook@chromium.org> wrote:
>> On Mon, Oct 17, 2022 at 09:45:21PM -0400, Paul Moore wrote:

[...]

>>> We can have defaults, like we do know, but I'm in no hurry to remove
>>> the ability to allow admins to change the ordering at boot time.
>>
>> My concern is with new LSMs vs the build system. A system builder will
>> be prompted for a new CONFIG_SECURITY_SHINY, but won't be prompted
>> about making changes to CONFIG_LSM to include it.
> 
> I would argue that if an admin/builder doesn't understand what a shiny
> new LSM does, they shouldn't be enabling that shiny new LSM.  Adding
> new, potentially restrictive, controls to your kernel build without a
> basic understanding of those controls is a recipe for disaster and I
> try to avoid recommending disaster as a planned course of action :)

It depends on what this shiny new LSMs do *by default*. In the case of 
Landlock, it do nothing unless a process does specific system calls 
(same as for most new kernel features: sysfs entries, syscall flags…). I 
guess this is the same for most LSMs.