linux-kernel - Re: [PATCH] binfmt_elf: fix PIE load with randomization disabled

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Message-ID: <alpine.LNX.2.00.1312092154350.24835@pobox.suse.cz>
Date:	Mon, 9 Dec 2013 21:57:19 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	"H.J. Lu" <hjl.tools@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Josh Boyer <jwboyer@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] binfmt_elf: fix PIE load with randomization disabled

On Mon, 9 Dec 2013, H.J. Lu wrote:

> Normally, a PIE executable has zero virtual address on the first PT_LOAD
> segment and kernel will load such executable at random address when
> randomization is enabled.  If randomization is disabled, kernel will load
> it at a fixed address.  But if a PIE executable has non-zero virtual
> address on the first PT_LOAD segment, kernel will load such executable
> at the non-zero virtual address when randomization is enabled. But when
> randomization is disabled, kernel ignores the non-zero virtual address
> at the non-zero virtual address when randomization is enabled. 

Hmm ... isn't actually this the thing that needs to be fixed instead? 

IOW, when randomization is enabled, is there a reason not to load on 
randomized address? (even if the first PT_LOAD segment has non-zero 
vaddr?)

> But when randomization is disabled, kernel ignores the non-zero virtual 
> address on the first PT_LOAD segment and loads it at the fixed address.  
> This patch makes kernel consistent by loading PIE executable with 
> non-zero virtual address at the non-zero virtual address, regardless if 
> randomization is enabled or disabled.

-- 
Jiri Kosina
SUSE Labs
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