Re: [PATCH] x86: Don't randomize stack unless current->personality permits it

[Al Boldi <a1426z@gawab.com>]

Frank van Maarseveen wrote:
> On Wed, Jul 12, 2006 at 06:03:18PM +0200, Andi Kleen wrote:
> > Al Boldi <a1426z@gawab.com> writes:
> > > Frank van Maarseveen wrote:
> > > > Do not randomize stack location unless current->personality permits
> > > > it.
>
> [...]
>
> > > 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
>
> Actually, randomize_stack_top() checks
>
> 	if (current->flags & PF_RANDOMIZE) {
>
> and it's only called from load_elf_binary() right after this:
>
> 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
> 		current->flags |= PF_RANDOMIZE;
>
> Further on create_elf_tables() is called and that one calls
> arch_align_stack() so maybe it is more appropriate to test (current->flags
> & PF_RANDOMIZE) in arch_align_stack() instead of recomputing it.

exec.c uses arch_align_stack() also for non-elf.

BTW, why does randomize_stack_top() mod against (8192*1024) instead of (8192) 
like arch_align_stack()?


Thanks!

--
Al

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