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Date: Tue, 9 Jan 2018 18:52:01 -0800
From: Eric Biggers <ebiggers3@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Joe Lawrence <joe.lawrence@redhat.com>,
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        "Luis R . Rodriguez" <mcgrof@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Eric Biggers <ebiggers@google.com>
Subject: Re: [PATCH 6/7] pipe: simplify round_pipe_size()
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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