Re: [PATCH] drm/nouveau: fix ramht wraparound

[Marcin Slusarz <marcin.slusarz-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Fri, Dec 21, 2012 at 10:15:48AM +1000, Ben Skeggs wrote:
> On Thu, Dec 20, 2012 at 11:37:12PM +0100, Marcin Slusarz wrote:
> > When hash collision occurs and it's near ramht object boundary, we could
> > read and possibly overwrite some memory after ramht object.
> > 
> > Signed-off-by: Marcin Slusarz <marcin.slusarz-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> > Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> > ---
> >  drivers/gpu/drm/nouveau/core/core/ramht.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/nouveau/core/core/ramht.c b/drivers/gpu/drm/nouveau/core/core/ramht.c
> > index 86a6404..6da314c 100644
> > --- a/drivers/gpu/drm/nouveau/core/core/ramht.c
> > +++ b/drivers/gpu/drm/nouveau/core/core/ramht.c
> > @@ -59,7 +59,7 @@ nouveau_ramht_insert(struct nouveau_ramht *ramht, int chid,
> >  		}
> >  
> >  		co += 8;
> > -		if (co >= nv_gpuobj(ramht)->size)
> > +		if (co + 8 > nv_gpuobj(ramht)->size)
> I might just be really tired, but, how exactly is the original wrong?
> The original could even just be (co == size) and still work correctly as
> far as I can tell.

Ah, crap, I didn't see that both hash value and ramht->size are divisible by 8.
So original code is correct (although it relies on the above) and my version
does not really fix anything.

Marcin