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

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Message-ID: <CAMe9rOoS6aZFCP=NNCcUuOanFcj0Y2Uq4jyC+KGC2qCR8M=s=A@mail.gmail.com>
Date:	Wed, 11 Dec 2013 05:41:32 -0800
From:	"H.J. Lu" <hjl.tools@...il.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Josh Boyer <jwboyer@...hat.com>
Subject: Re: [PATCH] binfmt_elf: fix PIE load with randomization disabled

On Wed, Dec 11, 2013 at 5:36 AM, Jiri Kosina <jkosina@...e.cz> wrote:
> On Mon, 9 Dec 2013, H.J. Lu wrote:
>
>> >> so that he could load his program compiled as PIE above 4GB.
>> >> If kernel is changed not to honor it, his program won't work any more.
>> >> In normal case, PIE has zero vaddr and this doesn't apply.
>> >>
>> >
>> > That doesn't seem to be PIE at all, and if it is PIE, then it should be
>> > relocatable (I agree btw with randomizing upward from the selected address.)
>>
>> Kernel can consider PIE with non-zero vaddr isn't real PIE.
>
> Why?
>
> I still think PIE with non-zero vaddr should be randomized by putting
> random offset to the vaddr. Don't you think so? Why?
>

When -Ttext-segment=XXX is used, the program is expected to
load at XXX, regardless -pie is used or not.  I will change the
linker to set type to ET_EXEC in this case so that it will be
independent of kernel.


-- 
H.J.
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