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

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Message-ID: <202211021501.88D8147@keescook>
Date:   Wed, 2 Nov 2022 15:02:44 -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 01:23:51PM -0700, Nathan Chancellor wrote:
> Right, I am not the biggest fan of this change myself and it is entirely
> possible that I am misreading the warnings from the commit message but I
> do not see how
> 
>         comp_node.comp.signal_u32_read = counter->ops->signal_read;
> 
> and
> 
>         comp_node.comp.count_u32_read = counter->ops->function_read;
> 
> in counter_add_watch(),
> 
>         comp.signal_u32_read = counter->ops->signal_read;
> 
> in counter_signal_attrs_create(), and
> 
>         comp.count_u32_read = counter->ops->function_read;
>         comp.count_u32_write = counter->ops->function_write;
> 
> in counter_count_attrs_create() are currently safe under kCFI, since the
> final parameter type of the prototypes in 'struct counter_ops' does not
> match the final parameter type of the prototypes in 'struct
> counter_comp'. I would expect the indirect calls in counter_get_data()
> and counter_comp_u32_show() to fail currently.

Ah! Thank you -- those were the places I couldn't find.

-- 
Kees Cook