linux-kernel - Re: [PATCH 10/10] LSM: Blob sharing support for S.A.R.A and LandLock

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Date:   Thu, 13 Sep 2018 17:06:16 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     John Johansen <john.johansen@...onical.com>,
        Paul Moore <paul@...l-moore.com>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        LKML <linux-kernel@...r.kernel.org>,
        SE Linux <selinux@...ho.nsa.gov>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        "Schaufler, Casey" <casey.schaufler@...el.com>
Subject: Re: [PATCH 10/10] LSM: Blob sharing support for S.A.R.A and LandLock

On Thu, Sep 13, 2018 at 5:03 PM, Casey Schaufler <casey@...aufler-ca.com> wrote:
> On 9/13/2018 4:51 PM, Kees Cook wrote:
>> So, before we can really make a decision, I think we have to decide:
>> should ordering be arbitrary for even this level of stacking?
>
> Do we have a case where it matters? I know that I could write a
> module that would have issues if one hook got called and another
> didn't because because a precursor module hook failed. I don't
> think that any of the existing modules have this problem.

FWIW, I prefer having explicit ordering that cannot be changed at
runtime. I'm just concerned about painting ourselves (further) into a
corner with security= suddenly gaining ordering semantics, but maybe I
can just ignore this and we can point and laugh at anyone who gets
burned by some future change to making it order-sensitive. :)

-Kees

-- 
Kees Cook
Pixel Security