[PATCH] pinctrl: nomadik: Add error handling for find_nmk_gpio_from_pin

[Wentao Liang <vulab@xxxxxxxxxxx>]

When find_nmk_gpio_from_pin fails to find a valid GPIO chip
for the given pin, the bit variable remains uninitialized. This
uninitialized value is then passed to __nmk_gpio_set_mode,
leading to undefined behavior and undesired address access.

To fix this, add error handling to check the return value of
find_nmk_gpio_from_pin. Log an error message indicating an
invalid pin offset and return -EINVAL immediately  If the function
fails.

Fixes: 75d270fda64d ("gpio: nomadik: request dynamic ID allocation")
Cc: stable@xxxxxxxxxxxxxxx # 6.9+
Signed-off-by: Wentao Liang <vulab@xxxxxxxxxxx>
---
 drivers/pinctrl/nomadik/pinctrl-nomadik.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/pinctrl/nomadik/pinctrl-nomadik.c b/drivers/pinctrl/nomadik/pinctrl-nomadik.c
index f4f10c60c1d2..4155137b0674 100644
--- a/drivers/pinctrl/nomadik/pinctrl-nomadik.c
+++ b/drivers/pinctrl/nomadik/pinctrl-nomadik.c
@@ -985,7 +985,7 @@ static int nmk_gpio_request_enable(struct pinctrl_dev *pctldev,
 				   unsigned int pin)
 {
 	struct nmk_pinctrl *npct = pinctrl_dev_get_drvdata(pctldev);
-	struct nmk_gpio_chip *nmk_chip;
+	struct nmk_gpio_chip *nmk_chip, *r;
 	struct gpio_chip *chip;
 	unsigned int bit;
 
@@ -1002,7 +1002,12 @@ static int nmk_gpio_request_enable(struct pinctrl_dev *pctldev,
 
 	dev_dbg(npct->dev, "enable pin %u as GPIO\n", pin);
 
-	find_nmk_gpio_from_pin(pin, &bit);
+	r = find_nmk_gpio_from_pin(pin, &bit);
+	if (!r) {
+		dev_err(npct->dev,
+			"invalid pin offset %d\n", pin);
+		return -EINVAL;
+	}
 
 	clk_enable(nmk_chip->clk);
 	/* There is no glitch when converting any pin to GPIO */
-- 
2.42.0.windows.2