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To: Al Boldi <a1426z@gawab.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: Don't randomize stack unless current->personality permits it
References: <200607112257.22069.a1426z@gawab.com>
From: Andi Kleen <ak@suse.de>
Date: 12 Jul 2006 18:03:18 +0200
In-Reply-To: <200607112257.22069.a1426z@gawab.com>
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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
-Andi