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From: Al Boldi <a1426z@gawab.com>
To: Andi Kleen <ak@suse.de>
Subject: Re: [PATCH] x86: Don't randomize stack unless current->personality permits it
Date: Wed, 12 Jul 2006 23:12:19 +0300
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Andi Kleen wrote:
> Al Boldi <a1426z@gawab.com> writes:
> > Frank van Maarseveen wrote:
> > > Do not randomize stack location unless current->personality permits
> > > it.
> > >
> > > Signed-off-by: Frank van Maarseveen <frankvm@frankvm.com>
> > > ---
> > >
> > > The problem seems also present in
> > >
> > >         arch/um/kernel/process_kern.c
> > >         arch/x86_64/kernel/process.c
> > >
> > >  arch/i386/kernel/process.c |    3 ++-
> > >  1 files changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff -rup a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
> > > --- a/arch/i386/kernel/process.c        2006-06-23 16:08:13.000000000
> > > +0200 +++ b/arch/i386/kernel/process.c        2006-07-11
> > > 14:39:20.000000000 +0200 @@ -38,6 +38,7 @@
> > >  #include <linux/kallsyms.h>
> > >  #include <linux/ptrace.h>
> > >  #include <linux/random.h>
> > > +#include <linux/personality.h>
> > >
> > >  #include <asm/uaccess.h>
> > >  #include <asm/pgtable.h>
> > > @@ -898,7 +899,7 @@ asmlinkage int sys_get_thread_area(struc
> > >
> > >  unsigned long arch_align_stack(unsigned long sp)
> > >  {
> > > -       if (randomize_va_space)
> > > +       if (!(current->personality & ADDR_NO_RANDOMIZE) &&
> > > randomize_va_space) sp -= get_random_int() % 8192;
> > >         return sp & ~0xf;
> > >  }
> >
> > It still blips on my system.
> >
> > echo 0 > /proc/sys/kernel/randomize_va_space makes the blips go away.
> >
> > ???
>
> fs/binfmt_elf.c:randomize_stack_top would need the same check

It already checks for it, but makes no difference.

Thanks for looking into this!

--
Al