gpiolib-sysfs: fix use-after-free in error path

When invoking device_create_with_groups() its return value is stored in data->cdev_base. However, in case of faiure, data is first freed and then derefernced in order to return data->cdev_base.

Fix the use-after-free by extracting the error
code before free'ing data.

This issue was reported by Coverity Scan.

Addresses-Coverity-ID: 1644512 ("Memory - illegal accesses (USE_AFTER_FREE)")

---
 drivers/gpio/gpiolib-sysfs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

index 956411fc467a..c4c21e25c682 100644
@@ -741,6 +741,7 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
 	struct gpiodev_data *data;
 	struct gpio_chip *chip;
 	struct device *parent;
+	int err;
 
 	/*
 	 * Many systems add gpio chips for SOC support very early,

@@ -781,8 +782,9 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
 						    GPIOCHIP_NAME "%d",
 						    chip->base);
 	if (IS_ERR(data->cdev_base)) {
+		err = PTR_ERR(data->cdev_base);
 		kfree(data);
-		return PTR_ERR(data->cdev_base);
+		return err;
 	}
 
 	return 0;

2.49.0

From: Bartosz Golaszewski <[email protected]>

Thanks for the catch. I tweaked the commit message and added the Fixes: tag. Applied, thanks!

[1/1] gpiolib-sysfs: fix use-after-free in error path

      https://git.kernel.org/brgl/linux/c/e6bb78570f7d531622ec572ef9ddbe6e66ff16ce

Best regards,

Bartosz Golaszewski <[email protected]>