linux-kernel - Re: StackProtector Oopses

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Message-ID: <20080422072933.751fe86f@laptopd505.fenrus.org>
Date:	Tue, 22 Apr 2008 07:29:33 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Reuben Farrelly <reuben-linuxkernel@...b.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: StackProtector Oopses - Re: 2.6.25-mm1

On Tue, 22 Apr 2008 10:34:08 +0200
Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Arjan van de Ven <arjan@...radead.org> wrote:
> 
> > > yeah. Arjan - any new patches to try that might fix the bootup
> > > test?
> > 
> > I've looked at the disassembly and compared it to mine, and the gcc
> > is doing something... rather unexpected. The only thing I can think
> > of is the patch below, it should make it a ton more robust...
> 
> > -	memset(&foo, 0, 2*sizeof(foo)); /* deliberate buffer
> > overflow */
> > +	if (current->stack_canary == *(((unsigned long *)&foo)+1))
> > +		*(((unsigned long *)&foo)+1) = 0;
> > +	else
> > +		printk(KERN_ERR "No -ftack-protector canary
> > found\n");
> 
> ok, i queued this up. (with the typo that Valdis noticed fixed)
> 
> but ... this bug needs to be figured out, not worked around.

well what I figured out was that the stack layout was "different".
Why/how I don't know, but being more robust against that is a good idea
in general.


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