linux-kernel - Re: [PATCH] binfmt_elf: randomize PIE binaries

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Date:	Thu, 19 Oct 2006 16:23:54 -0400
From:	Dave Jones <davej@...hat.com>
To:	Marcus Meissner <meissner@...e.de>
Cc:	linux-kernel@...r.kernel.org, akpm@...l.org
Subject: Re: [PATCH] binfmt_elf: randomize PIE binaries

On Thu, Oct 19, 2006 at 04:35:47PM +0200, Marcus Meissner wrote:

 > --- linux-2.6.18/fs/binfmt_elf.c.xx	2006-10-19 11:21:49.000000000 +0200
 > +++ linux-2.6.18/fs/binfmt_elf.c	2006-10-19 11:24:58.000000000 +0200
 > @@ -856,7 +856,12 @@ static int load_elf_binary(struct linux_
 >  			 * default mmap base, as well as whatever program they
 >  			 * might try to exec.  This is because the brk will
 >  			 * follow the loader, and is not movable.  */
 > -			load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
 > +			if (current->flags & PF_RANDOMIZE)
 > +				load_bias = randomize_range(0, ELF_ET_DYN_BASE,
 > +							    vaddr);
 > +			else
 > +				load_bias = ELF_ET_DYN_BASE - vaddr;
 > +			load_bias = ELF_PAGESTART(load_bias);
 >  		}
 >  
 >  		error = elf_map(bprm->file, load_bias + vaddr, elf_ppnt,


vaddr seems odd to be using as the len for randomize_range doesn't it ?
Should that be randomize_range(0, ELF_ET_DYN_BASE, ELF_ET_DYN_BASE - vaddr); 

maybe ?

Also, when we get to the elf_map(), we add vaddr back again, but in the
randomize_range case, we never subtracted it.  hmm?

	Dave

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