linux-kernel - Re: [PATCH 1/4] counter: Adjust final parameter type in function and signal callbacks

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Message-ID: <202211021216.FF49E84C69@keescook>
Date:   Wed, 2 Nov 2022 12:21:23 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     William Breathitt Gray <william.gray@...aro.org>,
        linux-iio@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Sami Tolvanen <samitolvanen@...gle.com>, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        Patrick Havelange <patrick.havelange@...ensium.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabrice Gasnier <fabrice.gasnier@...s.st.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Julien Panis <jpanis@...libre.com>,
        David Lechner <david@...hnology.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-omap@...r.kernel.org
Subject: Re: [PATCH 1/4] counter: Adjust final parameter type in function and
 signal callbacks

On Wed, Nov 02, 2022 at 10:22:14AM -0700, Nathan Chancellor wrote:
> The ->signal_u32_read(), ->count_u32_read(), and ->count_u32_write()
> callbacks in 'struct counter_comp' expect the final parameter to have a
> type of 'u32' or 'u32 *' but the ops functions that are being assigned
> to those callbacks have an enumerated type as the final parameter. While
> these are compatible from an ABI perspective, they will fail the
> aforementioned CFI checks.
> 
> Adjust the type of the final parameter in the ->signal_read(),
> ->function_read(), and ->function_write() callbacks in 'struct
> counter_ops' and their implementations to match the prototypes in
> 'struct counter_comp' to clear up these warnings and CFI failures.

I don't understand these changes. Where do 'struct counter_comp'
and 'struct counter_ops' get confused? I can only find matching
ops/assignments/calls, so I must be missing something. This looks like
a loss of CFI granularity instead of having wrappers added if there is
an enum/u32 conversion needed somewhere.

-- 
Kees Cook