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Date: Fri, 18 Apr 2008 00:28:58 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Arjan van de Ven <arjan@infradead.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Pekka Enberg <penberg@cs.helsinki.fi>, linux-usb@vger.kernel.org,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       James Morris <jmorris@namei.org>, Stephen Smalley <sds@tycho.nsa.gov>
Subject: Re: 2.6.25-mm1: not looking good
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On Fri, 18 Apr 2008 09:19:45 +0200 Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > On Thu, 17 Apr 2008 22:49:08 -0700 Arjan van de Ven <arjan@infradead.org> wrote:
> > 
> > > On Thu, 17 Apr 2008 16:03:31 -0700
> > > Andrew Morton <akpm@linux-foundation.org> wrote:
> > > 
> > > > 
> > > > I repulled all the trees an hour or two ago, installed everything on
> > > > an 8-way x86_64 box and:
> > > > 
> > > > 
> > > > stack-protector:
> > > > 
> > > > Testing -fstack-protector-all feature
> > > > No -fstack-protector-stack-frame!
> > > > -fstack-protector-all test failed
> > > 
> > > do you have a stack-protector capable GCC? I guess not.
> > > 
> > > This is a catch-22. You do not have stack-protector. Should we make that 
> > > a silent failure? or do you want to know that you don't have a security
> > > feature you thought you had.... complaining seems to be the right thing to do imo.
> > 
> > A #warning sounds more appropriate.
> 
> this warning is telling the user that the security feature that got 
> enabled in the .config is completely, 100% not working due to using a
> stack-protector-incapable GCC.

I doubt if anyone will care much.

> it's analogous as if there was a bug in gcc that made SELinux totally 
> ineffective in some mitigate-exploit-damage scenarios.

Not really.  In the selinux case we don't know that it'll break at compile
time.  

> No harm done on a 
> perfectly bug-free system - but once a bug happens that SELinux should 
> have mitigated, the breakage becomes real. Having a prominent warning is 
> the _minimum_.
> 
> having a build failure would be nice too because this is a build 
> environment problem. (not a build warning - warnings can easily be 
> missed because on a typical kernel build there's so many false positives 
> that get emitted by various other warning mechanisms) Arjan?
> 

Yeah, #error would work too.