linux-kernel - Re: [PATCH] iio: cros_ec_accel_legacy: Mark expected switch fall-throughs

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Message-ID: <CAGXu5jLsQ_Uc4kp=md2SrOERopjZmnQK_fAsru4MQUqEHRvEeA@mail.gmail.com>
Date:   Wed, 20 Feb 2019 10:20:39 -0800
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: cros_ec_accel_legacy: Mark expected switch fall-throughs

On Mon, Oct 8, 2018 at 10:24 AM Gustavo A. R. Silva
<gustavo@...eddedor.com> wrote:
>
> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> where we are expecting to fall through.
>
> Addresses-Coverity-ID: 1397962 ("Missing break in switch")
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/iio/accel/cros_ec_accel_legacy.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/iio/accel/cros_ec_accel_legacy.c b/drivers/iio/accel/cros_ec_accel_legacy.c
> index 063e89e..d609654 100644
> --- a/drivers/iio/accel/cros_ec_accel_legacy.c
> +++ b/drivers/iio/accel/cros_ec_accel_legacy.c
> @@ -385,8 +385,10 @@ static int cros_ec_accel_legacy_probe(struct platform_device *pdev)
>                 switch (i) {
>                 case X:
>                         ec_accel_channels[X].scan_index = Y;
> +                       /* fall through */
>                 case Y:
>                         ec_accel_channels[Y].scan_index = X;
> +                       /* fall through */
>                 case Z:
>                         ec_accel_channels[Z].scan_index = Z;
>                 }

Shouldn't these actually be "break;"s ? It seems like the loop is
stepping through X, Y, and Z. The _result_ is accidentally the same:

X: set X, Y, and Z
Y: set Y and Z
Z: set Z

result: X, Y, and Z are set correctly. But the code is technically wrong.


-- 
Kees Cook