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

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Date:   Fri, 15 Apr 2022 10:07:11 +0300
From:   Andrei Lalaev <andrei.lalaev@...id.com>
To:     linus.walleij@...aro.org, brgl@...ev.pl
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        andy.shevchenko@...il.com, Andrei Lalaev <andrei.lalaev@...id.com>
Subject: [PATCH v2] gpiolib: of: fix bounds check for 'gpio-reserved-ranges'

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.
---
 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