linux-kernel - Re: [PATCH v10 1/9] overflow: Allow mixed type arguments

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Date:   Sun, 11 Sep 2022 12:31:21 +0200
From:   Andi Shyti <andi.shyti@...ux.intel.com>
To:     Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>
Cc:     intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, mchehab@...nel.org,
        chris@...is-wilson.co.uk, matthew.auld@...el.com,
        thomas.hellstrom@...ux.intel.com, jani.nikula@...el.com,
        nirmoy.das@...el.com, airlied@...hat.com, daniel@...ll.ch,
        andi.shyti@...ux.intel.com, andrzej.hajda@...el.com,
        keescook@...omium.org, mauro.chehab@...ux.intel.com,
        linux@...musvillemoes.dk, vitor@...saru.org, dlatypov@...gle.com,
        ndesaulniers@...gle.com
Subject: Re: [PATCH v10 1/9] overflow: Allow mixed type arguments

Hi Kees,

On Fri, Sep 09, 2022 at 07:59:05PM +0900, Gwan-gyeong Mun wrote:
> From: Kees Cook <keescook@...omium.org>
> 
> When the check_[op]_overflow() helpers were introduced, all arguments were
> required to be the same type to make the fallback macros simpler. However,
> now that the fallback macros have been removed[1], it is fine to allow
> mixed types, which makes using the helpers much more useful, as they
> can be used to test for type-based overflows (e.g. adding two large ints
> but storing into a u8), as would be handy in the drm core[2].
> 
> Remove the restriction, and add additional self-tests that exercise some
> of the mixed-type overflow cases, and double-check for accidental macro
> side-effects.

I would split in two different patches the check_[op]_overflow()
helpers with the tests.

Overall they look good though.

> [1] https://git.kernel.org/linus/4eb6bd55cfb22ffc20652732340c4962f3ac9a91
> [2] https://lore.kernel.org/lkml/20220824084514.2261614-2-gwan-gyeong.mun@intel.com
> 
> Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
> Cc: Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>
> Cc: Andrzej Hajda <andrzej.hajda@...el.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Gwan-gyeong, can you please add your SoB here? And you don't need
to 'Cc:' yourself.

Andi