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Date:   Sat, 29 Oct 2022 00:08:53 -0700
From:   Kees Cook <>
To:     "Gustavo A. R. Silva" <>
Cc:     Kalle Valo <>,
        "David S. Miller" <>,
        Eric Dumazet <>,
        Jakub Kicinski <>,
        Paolo Abeni <>,,,,
Subject: Re: [PATCH v2 3/6] zd1201: Avoid clashing function prototypes

On Thu, Oct 27, 2022 at 03:19:19PM -0500, Gustavo A. R. Silva wrote:
> When built with Control Flow Integrity, function prototypes between
> caller and function declaration must match. These mismatches are visible
> at compile time with the new -Wcast-function-type-strict in Clang[1].
> Fix a total of 30 warnings like these:
> ../drivers/net/wireless/zydas/zd1201.c:1560:2: warning: cast from 'int (*)(struct net_device *, struct iw_request_info *, struct iw_freq *, char *)' to 'iw_handler' (aka 'int (*)(struct net_device *, struct iw_request_info *, union iwreq_data *, char *)') converts to incompatible function type [-Wcast-function-type-strict]
>         (iw_handler) zd1201_set_freq,           /* SIOCSIWFREQ */
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> The zd1201 Wireless Extension handler callbacks (iw_handler) use a
> union for the data argument. Actually use the union and perform explicit
> member selection in the function body instead of having a function
> prototype mismatch.There are no resulting binary differences
> before/after changes.
> Link:
> Link: [1]
> Signed-off-by: Gustavo A. R. Silva <>

This looks right to me. I've got half a cocci script that spits out
something close says interdiff. :)

Reviewed-by: Kees Cook <>

Kees Cook

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