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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Andrei Lalaev <andrei.lalaev@emlid.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <brgl@bgdev.pl>
Subject: [PATCH 5.4 04/52] gpiolib: of: fix bounds check for gpio-reserved-ranges
Date:   Tue, 10 May 2022 15:07:33 +0200
Message-Id: <20220510130729.984881193@linuxfoundation.org>
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From: Andrei Lalaev <andrei.lalaev@emlid.com>

commit e75f88efac05bf4e107e4171d8db6d8c3937252d upstream.

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.

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.

Fixes: 726cb3ba4969 ("gpiolib: Support 'gpio-reserved-ranges' property")
Signed-off-by: Andrei Lalaev <andrei.lalaev@emlid.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpio/gpiolib-of.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -783,7 +783,7 @@ static void of_gpiochip_init_valid_mask(
 					   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);