linux-kernel - Re: [PATCH v2 05/20] randstruct: Whitelist struct security_hook

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Date:   Tue, 30 May 2017 20:34:30 +1000 (AEST)
From:   James Morris <jmorris@...ei.org>
To:     Kees Cook <keescook@...omium.org>
cc:     Christoph Hellwig <hch@...radead.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        James Morris <james.l.morris@...cle.com>,
        Laura Abbott <labbott@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v2 05/20] randstruct: Whitelist struct security_hook_heads
 cast

On Sat, 27 May 2017, Kees Cook wrote:

> On Sat, May 27, 2017 at 1:41 AM, Christoph Hellwig <hch@...radead.org> wrote:
> > On Fri, May 26, 2017 at 01:17:09PM -0700, Kees Cook wrote:
> >> The LSM initialization routines walk security_hook_heads as an array
> >> of struct list_head instead of via names to avoid a ton of needless
> >> source. Whitelist this to avoid the false positive warning from the
> >> plugin:
> >
> > I think this crap just needs to be fixed properly.  If not it almost
> > defeats the protections as the "security" ops are just about everywhere.
> 
> There's nothing unsafe about 3dfc9b02864b19f4dab376f14479ee4ad1de6c9e,
> it just avoids tons of needless code. 

Removing needless code is a security feature, ideally.

> Tetsuo has some other ideas for
> cleaning it up further, but I don't like it because it removes
> compile-time verification of function types. There have been a lot of
> trade-offs in getting this working correctly, so I don't have any
> problem with how it looks currently. It's just a collision of
> assumptions between randstruct (omg, you're accessing a randomized
> struct with a different struct!) and the security head list (all
> entries are lists, and we're just initializing them).

Fix randstruct perhaps, rather than modifying kernel code to shut it up.

-- 
James Morris
<jmorris@...ei.org>