Re: [PATCH] mm/gup: Do not return 0 from pin_user_pages_fast() for bad args

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Jun 21, 2023 at 01:24:14PM +0200, David Hildenbrand wrote:
> > diff --git a/mm/gup.c b/mm/gup.c
> > index bbe4162365933e..36c587fec574fd 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -2969,7 +2969,7 @@ static int internal_get_user_pages_fast(unsigned long start,
> >   	start = untagged_addr(start) & PAGE_MASK;
> >   	len = nr_pages << PAGE_SHIFT;
> >   	if (check_add_overflow(start, len, &end))
> > -		return 0;
> > +		return -EOVERFLOW;
> 
> I'm curious if there is any sane use case where that could actually trigger.
> Smells like something that should be a WARN_ON_ONCE(), but maybe some
> callers simply pass through what user-space gave them.

Yes, that is pretty common to just pass through.

Thanks,
Jason