linux-hardening - Re: i915 utils: range

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Message-ID: <202506021119.8FD6339F@keescook>
Date: Mon, 2 Jun 2025 11:20:51 -0700
From: Kees Cook <kees@...nel.org>
To: Jani Nikula <jani.nikula@...el.com>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-hardening@...r.kernel.org, intel-gfx@...ts.freedesktop.org
Subject: Re: i915 utils: range_overflows*()

On Mon, Jun 02, 2025 at 04:10:21PM +0300, Jani Nikula wrote:
> On Fri, 30 May 2025, Kees Cook <kees@...nel.org> wrote:
> > On Fri, May 30, 2025 at 10:44:31AM +0300, Jani Nikula wrote:
> >> 
> >> Hi Kees -
> >> 
> >> drivers/gpu/drm/i915/i915_utils.h has a handful of helper macros for
> >> checking range overflows: range_overflows(), range_overflows_t(),
> >> range_overflows_end(), and range_overflows_end_t().
> >> 
> >> Looks like the first one has also been copy-pasted to
> >> include/drm/drm_buddy.h.
> >> 
> >> Feels like include/linux/overflow.h would be the right place for (some
> >> version of) them.
> >> 
> >> Thoughts?
> >
> > Sure, yes! They need some documentation too. :) And probably some
> > renaming. It looks like range_overflows() is not end-inclusive, but
> > range_overflows_end() is? And the _t variants are forcing explicit
> > types (like max_t, but unlike struct_size_t).
> 
> Ah, naming.
> 
> As we all know, NP in NP-complete actually stands for "naming
> problem". It's hard to come up with a good name, but presented with one,
> it's quick to verify it is indeed good.
> 
> Ideas for the hard part?

Well, since the users already exist with the current names, how about we
skip that for now and just relocate these (with added kern-doc) to
overflow.h and go from there?

-Kees

-- 
Kees Cook