linux-hardening - Re: [PATCH v5 3/3] overflow: Introduce wrapping_inc() and wrapping

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Date: Wed, 7 Feb 2024 17:31:54 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Kees Cook <keescook@...omium.org>
Cc: Andy Shevchenko <andy@...nel.org>, Rasmus Villemoes <rasmus.villemoes@...vas.dk>, 
	Marco Elver <elver@...gle.com>, Eric Biggers <ebiggers@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, "Gustavo A. R. Silva" <gustavoars@...nel.org>, 
	linux-hardening@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/3] overflow: Introduce wrapping_inc() and wrapping_dec()

On Wed, Feb 7, 2024 at 5:24 PM Kees Cook <keescook@...omium.org> wrote:
>
> This allows replacements of the idioms "var += offset" and "var -= offset"
> with the wrapping_inc() and wrapping_dec() helpers respectively. They
> will avoid wrap-around sanitizer instrumentation.
>
> Add to the selftests to validate behavior and lack of side-effects.

I would expect inc/dec to add/subtract 1. So, to me the terminology is
confusing. The list of the C/C++ operators on Wikipedia describes
above as

+= Assignment by sum
-= Assignment by difference


Hence the proposal is to have

wrapping_sum()
wrapping_diff()

-- 
With Best Regards,
Andy Shevchenko