linux-kernel - Re: [PATCH] [BUGFIX] gpio: reject invalid gpio before getting gpio

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Date:   Sun, 30 Jul 2017 19:21:36 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Masami Hiramatsu <masami.hiramatsu@...aro.org>,
        Jassi Brar <jaswinder.singh@...aro.org>
Subject: Re: [PATCH] [BUGFIX] gpio: reject invalid gpio before getting gpio_desc

On Sat, Jul 29, 2017 at 11:00 AM, Masami Hiramatsu <mhiramat@...nel.org> wrote:
> Check user-given gpio number and reject it before
> calling gpio_to_desc() because gpio_to_desc() is
> for kernel driver and it expects given gpio number
> is valid (means 0 to 511).

> If given number is invalid, gpio_to_desc() calls
> WARN() and dump registers and stack for debug.
> This means user can easily kick WARN() just by
> writing invalid gpio number (e.g. 512) to
> /sys/class/gpio/export.

> This bug has been introduced by commit 0e9a5edf5d01
> ("gpio: fix deferred probe detection for legacy API")

Why so narrow paraghraps? We don't do two column articles :-)

> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> Fixes: commit 0e9a5edf5d01 ("gpio: fix deferred probe detection for legacy API")

If you use git tools directly, like

% git commit -s --amend

you will immediately notice that your SoB line is supposed to be the last one.

Besides above, word "commit" is not needed in Fixes: tag IIRC.


> --- a/drivers/gpio/gpiolib-sysfs.c
> +++ b/drivers/gpio/gpiolib-sysfs.c
> @@ -2,6 +2,7 @@
>  #include <linux/mutex.h>
>  #include <linux/device.h>
>  #include <linux/sysfs.h>
> +#include <linux/gpio.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/gpio/driver.h>
>  #include <linux/interrupt.h>

> @@ -443,14 +444,16 @@ static ssize_t export_store(struct class *class,

> -       struct gpio_desc        *desc;
> +       struct gpio_desc        *desc = NULL;

> -       desc = gpio_to_desc(gpio);
> +       if (gpio_is_valid(gpio))
> +               desc = gpio_to_desc(gpio);

Twice repeatition is a candidate for a helper, like:

static inline struct gpio_desc *gpio_to_valid_desc(int gpio)
{
 return gpio_is_valid(gpio) ? gpio_to_desc(gpio) : NULL;
}

-- 
With Best Regards,
Andy Shevchenko