On Sat, Jun 01, 2019 at 09:14:17AM -0700, Linus Torvalds wrote:
> On Sat, Jun 1, 2019 at 12:50 AM Christoph Hellwig <hch@xxxxxx> wrote:
> >
> > Pass in the already calculated end value instead of recomputing it, and
> > leave the end > start check in the callers instead of duplicating them
> > in the arch code.
>
> Good cleanup, except it's wrong.
>
> > - if (nr_pages <= 0)
> > + if (end < start)
> > return 0;
>
> You moved the overflow test to generic code - good.
>
> You removed the sign and zero test on nr_pages - bad.
I only removed a duplicate of it. The full (old) code in
get_user_pages_fast() looks like this:
if (nr_pages <= 0)
return 0;
if (unlikely(!access_ok((void __user *)start, len)))
return -EFAULT;
if (gup_fast_permitted(start, nr_pages)) {
