linux-kernel - Re: [PATCH v4 00/19] LSM: Module stacking for SARA and Landlock

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Message-ID: <CAGXu5j+7FpFDNuOowdHzJ5RXgfETQMv=Fe-EU1gWo+nWK+goZA@mail.gmail.com>
Date:   Sat, 22 Sep 2018 19:43:36 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     LSM <linux-security-module@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        SE Linux <selinux@...ho.nsa.gov>,
        LKLM <linux-kernel@...r.kernel.org>,
        John Johansen <john.johansen@...onical.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Salvatore Mesoraca <s.mesoraca16@...il.com>
Subject: Re: [PATCH v4 00/19] LSM: Module stacking for SARA and Landlock

On Sat, Sep 22, 2018 at 9:38 AM, Casey Schaufler <casey@...aufler-ca.com> wrote:
> On 9/21/2018 8:02 PM, Kees Cook wrote:
>> On Fri, Sep 21, 2018 at 4:59 PM, Casey Schaufler <casey@...aufler-ca.com> wrote:
>>> v4: Finer granularity in the patches and other
>>>     cleanups suggested by Kees Cook.
>>>     Removed dead code created by the removal of SELinux
>>>     credential blob poisoning.
>> Thanks for the splitting, this really does make it easier to review
>> (at least for me). I think this looks really good, though obviously
>> I'd like to refactor it slightly on top of my series. :)
>
> Whichever goes on top is fine with me. What's one
> more patch set merge, after all?
>
>> One additional thought I had was about the blobs allocations: some are
>> separate kmem caches, and some are kmalloc. I'm thinking it might make
>> sense to use separate kmem caches for two reasons:
>
> I had seriously considered doing that. I can't see any reason
> not to. It's something that could be done at any time, and with
> all the other things that had to change it just didn't get in.

Yup; that is an easy future change. Not needed now!

>
>> - they're going to always be the same size and are regularly
>> allocated/freed, so it may offer a performance benefit.
>>
>> - they're explicitly not supposed to be exposed to userspace, so
>> hardened usercopy would protect them if they were not kmalloc()ed.
>>
>> I'm excited about getting this landed!
>
> Soon. Real soon. I hope. I would very much like for
> someone from the SELinux camp to chime in, especially on
> the selinux_is_enabled() removal.

Agreed.

> On a somewhat related note, I will be out for the first three
> weeks of October, returning just in time for the Linux Security
> Summit in Edinburgh. My connectivity will be severely limited.
> I don't expect to accomplish anything while I'm out.

If you're okay with it, I can help with changes while you're out -- I
want to try to rebase it on my tree and see how it looks anyway. :)

-Kees

-- 
Kees Cook
Pixel Security