linux-kernel - Re: [RFC PATCH] binfmt_elf: Fix PIE execution with randomization disabled

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Message-ID: <alpine.LNX.2.00.1110031651400.31654@pobox.suse.cz>
Date:	Mon, 3 Oct 2011 16:53:34 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Josh Boyer <jwboyer@...hat.com>
Cc:	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Andrew Morton <akpm00@...il.com>, Ingo Molnar <mingo@...e.hu>,
	hongjiu.lu@...el.com, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <rmk@....linux.org.uk>
Subject: Re: [RFC PATCH] binfmt_elf: Fix PIE execution with randomization
 disabled

On Thu, 29 Sep 2011, Josh Boyer wrote:

> Perhaps another check here for randomize?  Something like:
> 
> #if defined(CONFIG_X86) || defined(CONFIG_ARM)
> 		if (current->flags & PF_RANDOMIZE)
> 			load_bias = 0;
> 		else if (vaddr)
> 			load_bias = 0;
> 		else
> 			load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE);
> #else
> 		load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
> #endif
> 
> If that's stupid, then feel free to tell me.  I won't pretend like I
> understand what is going on here yet, but based on the explanation you
> provided that might work.

I have just verified my hunch that the original patch from H.J. / Josh 
breaks ASLR completely, so Andrew, please drop it for now.

I am now looking into how to fix things properly.

Josh, looking at what you are proposing -- do you see any reason to make 
the behavior different in #else branch and in !(current->flags & 
PF_RANDOMIZE) case?

-- 
Jiri Kosina
SUSE Labs
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