Re: [PATCH v5] RO/NX protection for loadable kernel modules

[Jesper Nilsson <jesper.nilsson@axis.com>]

On Sun, Jul 12, 2009 at 06:40:39AM +0200, Rusty Russell wrote:
> On Sun, 12 Jul 2009 01:19:58 am Arjan van de Ven wrote:
> > Rusty Russell <rusty@rustcorp.com.au> wrote:
> > > I have a question about this patch though: I think it's unsafe in
> > > general to mark the last partial page as NX (we asked for executable
> > > pages, this could remove executable from some unrelated allocation).
> >
> > we vmalloc / g_f_p modules right? so we don't share the last page.
> 
> Historically yes, but I don't think we should be counting on it.  It makes 
> sense to kmalloc for small modules, and it's arch specific code.
> 
> OTOH, a quick grep shows currently only cris does kmalloc, and that's a config
> option.

...which is a not often used debug option.

> It might be time to unify this code.  If we rename MODULE_START to 
> MODULE_VADDR on MIPS, then ignoring CRIS there's only two real variants; 
> vmalloc and __vmalloc.
> 
> (I like the idea of trying kmalloc and falling back, simply because it reduces 
> TLB pressure, but that's probably best done after unification).
> 
> Thoughts?
> Rusty.

/^JN - Jesper Nilsson
-- 
               Jesper Nilsson -- jesper.nilsson@axis.com