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

[Josh Boyer <jwboyer@redhat.com>]

On Mon, Oct 03, 2011 at 04:53:34PM +0200, Jiri Kosina wrote:
> 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.

Yes, please drop the original.

> 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?

I was mostly just trying to adapt H.J.'s patch to account for the
PF_RANDOMIZE case.  Looking at it a bit more, I'm not sure why they
would need to be different.  H.J., do you recall why you made that
change originally?

josh