Re: [PATCH 6/7] pipe: simplify round_pipe_size()

[Eric Biggers <ebiggers3@gmail.com>]

On Tue, Jan 09, 2018 at 02:27:10PM -0800, Kees Cook wrote:
> 
> > @@ -1054,9 +1048,6 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
> >                 return -EINVAL;
> >         nr_pages = size >> PAGE_SHIFT;
> >
> > -       if (!nr_pages)
> > -               return -EINVAL;
> > -
> 
> I would just leave this hunk anyway: it's defensive for any future
> changes. Maybe add a comment describing why it's currently redundant?
> 

I don't know; I find it really confusing to have two slightly different checks
for the same thing, as it implies that they actually need to be there for a
reason.  How about just checking nr_pages?

        size = round_pipe_size(arg);
        nr_pages = size >> PAGE_SHIFT;

        if (nr_pages == 0)
                return -EINVAL;

Eric