linux-kernel - Re: [PATCH] brk: COMPAT_BRK: fix detection of randomized brk (was Re: [regression v2.6.38] Re: [PATCH v2] brk: fix min_brk lower bound computation forCOMPAT

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Message-ID: <alpine.LNX.2.00.1104061341550.5855@pobox.suse.cz>
Date:	Wed, 6 Apr 2011 13:42:44 -0700 (PDT)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Linux/m68k <linux-m68k@...r.kernel.org>
Subject: Re: [PATCH] brk: COMPAT_BRK: fix detection of randomized brk (was
 Re: [regression v2.6.38] Re: [PATCH v2] brk: fix min_brk lower bound
 computation forCOMPAT_BRK)

On Wed, 6 Apr 2011, Geert Uytterhoeven wrote:

> > From: Jiri Kosina <jkosina@...e.cz>
> > Subject: brk: COMPAT_BRK: fix detection of randomized brk
> >
> > 5520e89 ("brk: fix min_brk lower bound computation for COMPAT_BRK")
> > tried to get the whole logic of brk randomization for legacy (libc5-based)
> > applications finally right.
> >
> > It turns out that the way to detect whether brk has actually been randomized in
> > the end or not introduced by that patch still doesn't work for those binaries,
> > as reported by Geert.
> >
> > I don't like it, but currently see no better option than a bit flag in
> > task_struct to catch the CONFIG_COMPAT_BRK && randomize_va_space == 2
> > case.
> >
> > Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> > Tested-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> > ---
> >
> > I am not really happy about introducing the bit flag, but I currently
> > don't see another option. And it's only for the legacy CONFIG_COMPAT_BRK
> > case anyway.
> >
> > Andrew, Ingo, any opinions/objections?
> >
> > If not -- Andrew, I guess this should go into current -rc still.
> 
> And in 2.6.38-stable.
> 
> Does anyone still have libc5 binaries for i386?

The first time we introduced brk randomization, Pavel Machek reported a 
problem with some libc5-based binary on some ancient x86 system he had.

So I am afraid there still might be sparse occurences out there.

-- 
Jiri Kosina
SUSE Labs, Novell Inc.
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