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

Kees Cook
2018-01-10T03:13:38Z

On Tue, Jan 9, 2018 at 6:52 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
> 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;

Oh yeah! I like that.

-Kees

--
Kees Cook
Pixel Security