> Yeah, you'll need to change the PTEs for those pages you created by
> calling get_user_page() by calling an mprotect like function; perhaps
> something like:

Thanks.  I've incorporated your changes (updated patch attached).

> > +               /* Move stack pages down in memory. */
> > +               if (stack_shift) {
> > +                       // FIXME: Verify the shift is OK.
> > +
>
> What exactly are you wondering about? the call to move_vma looks sane to
> me

My concern was that the binfmt handler may have setup other vm areas
which overlap the new range.  The move_vma() function doesn't do
overlap checking.  I'm not sure if this is something I need to guard
against, or if it falls in the "Don't do that!" category.

Ollie