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

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Message-ID: <CAGXu5jK=+FuL+JiSxcHy0i9Ppha=BQYdJW5zvbm1Redbo12wmw@mail.gmail.com>
Date:   Fri, 21 Sep 2018 20:02:57 -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 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. :)

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:

- 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!

-Kees

-- 
Kees Cook
Pixel Security