linux-kernel - Re: [PATCH v2] gpiolib: of: fix bounds check for 'gpio-reserved-ranges'

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Date:   Mon, 25 Apr 2022 21:01:05 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andrei Lalaev <andrei.lalaev@...id.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v2] gpiolib: of: fix bounds check for 'gpio-reserved-ranges'

On Fri, Apr 15, 2022 at 9:09 AM Andrei Lalaev <andrei.lalaev@...id.com> wrote:
>
> Gpiolib interprets the elements of "gpio-reserved-ranges" as "start,size"
> because it clears "size" bits starting from the "start" bit in the according
> bitmap. So it has to use "greater" instead of "greater or equal" when performs
> bounds check to make sure that GPIOs are in the available range.
> Previous implementation skipped ranges that include the last GPIO in
> the range.
>
> Fixes: 726cb3ba4969 ("gpiolib: Support 'gpio-reserved-ranges' property")
> Signed-off-by: Andrei Lalaev <andrei.lalaev@...id.com>
> ---
> I wrote the mail to the maintainers
> (https://lore.kernel.org/linux-gpio/20220412115554.159435-1-andrei.lalaev@emlid.com/T/#u)
> of the questioned DTSes (because I couldn't understand how the maintainers
> interpreted this property), but I haven't received a response.
> Since the questioned DTSes use "gpio-reserved-ranges = <0 4>"
> (i.e., the beginning of the range), this patch doesn't affect these DTSes at all.
> TBH this patch doesn't break any existing DTSes because none of them
> reserve gpios at the end of range.
> ---

Queued for fixes and Cc'ed stable, thanks! I also added the part below
the tags to the commit message as it's important so I don't want to
drop it from history.

Bart

>  drivers/gpio/gpiolib-of.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
> index ae1ce319cd78..7e5e51d49d09 100644
> --- a/drivers/gpio/gpiolib-of.c
> +++ b/drivers/gpio/gpiolib-of.c
> @@ -910,7 +910,7 @@ static void of_gpiochip_init_valid_mask(struct gpio_chip *chip)
>                                            i, &start);
>                 of_property_read_u32_index(np, "gpio-reserved-ranges",
>                                            i + 1, &count);
> -               if (start >= chip->ngpio || start + count >= chip->ngpio)
> +               if (start >= chip->ngpio || start + count > chip->ngpio)
>                         continue;
>
>                 bitmap_clear(chip->valid_mask, start, count);
> --
> 2.25.1
>