[PATCH] char: scx200_gpio: check cdev_add() return value

[PATCH] char: scx200_gpio: check cdev_add() return value

[Linkai Gong]

cdev_add() can fail. The driver currently ignores the return value and
reports probe success even when the cdev was not registered, leaving a
chrdev region allocated with no working file operations.

Check the return value, emit an error, and unwind the chrdev region and
platform device on failure.

Fixes: 635adb6cd25c ("[PATCH] scx200_gpio: use 1 cdev for N minors, not N for N")
Signed-off-by: Linkai Gong <gonglinkai@kylinos.cn>
---
 drivers/char/scx200_gpio.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/char/scx200_gpio.c b/drivers/char/scx200_gpio.c
index 700e6affea6f..d9d66d4c2312 100644
--- a/drivers/char/scx200_gpio.c
+++ b/drivers/char/scx200_gpio.c
@@ -107,10 +107,16 @@ static int __init scx200_gpio_init(void)
 	}
 
 	cdev_init(&scx200_gpio_cdev, &scx200_gpio_fileops);
-	cdev_add(&scx200_gpio_cdev, devid, MAX_PINS);
+	rc = cdev_add(&scx200_gpio_cdev, devid, MAX_PINS);
+	if (rc < 0) {
+		dev_err(&pdev->dev, "cdev_add err: %d\n", rc);
+		goto undo_chrdev_region;
+	}
 
 	return 0; /* succeed */
 
+undo_chrdev_region:
+	unregister_chrdev_region(devid, MAX_PINS);
 undo_platform_device_add:
 	platform_device_del(pdev);
 undo_malloc:
-- 
2.25.1

Re: [PATCH] char: scx200_gpio: check cdev_add() return value

[Greg Kroah-Hartman]

On Thu, Jul 30, 2026 at 05:53:21PM +0800, Linkai Gong wrote:
> cdev_add() can fail. The driver currently ignores the return value and
> reports probe success even when the cdev was not registered, leaving a
> chrdev region allocated with no working file operations.
> 
> Check the return value, emit an error, and unwind the chrdev region and
> platform device on failure.
> 
> Fixes: 635adb6cd25c ("[PATCH] scx200_gpio: use 1 cdev for N minors, not N for N")
> Signed-off-by: Linkai Gong <gonglinkai@kylinos.cn>
> ---
>  drivers/char/scx200_gpio.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/char/scx200_gpio.c b/drivers/char/scx200_gpio.c
> index 700e6affea6f..d9d66d4c2312 100644
> --- a/drivers/char/scx200_gpio.c
> +++ b/drivers/char/scx200_gpio.c
> @@ -107,10 +107,16 @@ static int __init scx200_gpio_init(void)
>  	}
>  
>  	cdev_init(&scx200_gpio_cdev, &scx200_gpio_fileops);
> -	cdev_add(&scx200_gpio_cdev, devid, MAX_PINS);
> +	rc = cdev_add(&scx200_gpio_cdev, devid, MAX_PINS);
> +	if (rc < 0) {

Should just be:
	if (rc) {

right?

thanks,

greg k-h