linux-kernel - Re: [PATCH v3 1/3] security: Introduce LSM_ORDER

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Date:   Fri, 10 Mar 2023 08:57:36 +0100
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     Paul Moore <paul@...l-moore.com>
Cc:     zohar@...ux.ibm.com, dmitry.kasatkin@...il.com, jmorris@...ei.org,
        serge@...lyn.com, mic@...ikod.net, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, keescook@...omium.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v3 1/3] security: Introduce LSM_ORDER_LAST and set it
 for the integrity LSM

On Thu, 2023-03-09 at 18:44 -0500, Paul Moore wrote:
> On Thu, Mar 9, 2023 at 3:55 AM Roberto Sassu
> <roberto.sassu@...weicloud.com> wrote:
> > From: Roberto Sassu <roberto.sassu@...wei.com>
> > 
> > Introduce LSM_ORDER_LAST, to satisfy the requirement of LSMs needing to be
> > last, e.g. the 'integrity' LSM, without changing the kernel command line or
> > configuration.
> > 
> > Also, set this order for the 'integrity' LSM. While not enforced, this is
> > the only LSM expected to use it.
> > 
> > Similarly to LSM_ORDER_FIRST, LSMs with LSM_ORDER_LAST are always enabled
> > and put at the end of the LSM list.
> 
> Since you are respinning this patchset anyway, I might make it clear
> that the LSM_ORDER_LAST LSMs are always enabled only when they are
> enabled at kernel configure/build time.  Simply marking a LSM as
> LSM_ORDER_LAST does not mean you don't have to explicitly select the
> LSM in the rest of the Kconfig.

Ok, yes, better to clarify.

Thanks

Roberto

> > Finally, for LSM_ORDER_MUTABLE LSMs, set the found variable to true if an
> > LSM is found, regardless of its order. In this way, the kernel would not
> > wrongly report that the LSM is not built-in in the kernel if its order is
> > LSM_ORDER_LAST.
> > 
> > Fixes: 79f7865d844c ("LSM: Introduce "lsm=" for boottime LSM selection")
> > Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> > ---
> >  include/linux/lsm_hooks.h |  1 +
> >  security/integrity/iint.c |  1 +
> >  security/security.c       | 12 +++++++++---
> >  3 files changed, 11 insertions(+), 3 deletions(-)