Re: [PATCH] brk: COMPAT_BRK: fix detection of randomized brk (wasRe: [regression v2.6.38] Re: [PATCH v2] brk: fix min_brk lower boundcomputation forCOMPAT_BRK)

[Jiri Kosina]

On Wed, 6 Apr 2011, Geert Uytterhoeven wrote:

> > From: Jiri Kosina <jkosina@xxxxxxx>
> > 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@xxxxxxx>
> > Tested-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > ---
> >
> > 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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