Re: [PATCH RESEND 1/5] leds: leds-st1202: fix NULL pointer access on race condition

[Lee Jones <lee@kernel.org>]

On Sat, 01 Feb 2025, Manuel Fombuena wrote:

> st1202_dt_init() calls devm_led_classdev_register_ext() before the
> internal data structures are properly setup, so the leds become visible
> to user space while being partially initialized, leading to a window
> where trying to access them causes a NULL pointer access.

If this is true, you need to provide a Fixes: tag and to Cc: Stable.

Documentation/process/stable-kernel-rules.rst

> This change moves devm_led_classdev_register_ext() to the last thing to
> happen during initialization to eliminate it.
> 
> Signed-off-by: Manuel Fombuena <fombuena@outlook.com>
> ---
>  drivers/leds/leds-st1202.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/leds/leds-st1202.c b/drivers/leds/leds-st1202.c
> index b691c4886993..e894b3f9a0f4 100644
> --- a/drivers/leds/leds-st1202.c
> +++ b/drivers/leds/leds-st1202.c
> @@ -261,8 +261,6 @@ static int st1202_dt_init(struct st1202_chip *chip)
>  	int err, reg;
>  
>  	for_each_available_child_of_node_scoped(dev_of_node(dev), child) {
> -		struct led_init_data init_data = {};
> -
>  		err = of_property_read_u32(child, "reg", &reg);
>  		if (err)
>  			return dev_err_probe(dev, err, "Invalid register\n");
> @@ -276,15 +274,6 @@ static int st1202_dt_init(struct st1202_chip *chip)
>  		led->led_cdev.pattern_set = st1202_led_pattern_set;
>  		led->led_cdev.pattern_clear = st1202_led_pattern_clear;
>  		led->led_cdev.default_trigger = "pattern";
> -
> -		init_data.fwnode = led->fwnode;
> -		init_data.devicename = "st1202";
> -		init_data.default_label = ":";
> -
> -		err = devm_led_classdev_register_ext(dev, &led->led_cdev, &init_data);
> -		if (err < 0)
> -			return dev_err_probe(dev, err, "Failed to register LED class device\n");
> -
>  		led->led_cdev.brightness_set = st1202_brightness_set;
>  		led->led_cdev.brightness_get = st1202_brightness_get;
>  	}
> @@ -368,6 +357,7 @@ static int st1202_probe(struct i2c_client *client)
>  		return ret;
>  
>  	for (int i = 0; i < ST1202_MAX_LEDS; i++) {
> +		struct led_init_data init_data = {};
>  		led = &chip->leds[i];
>  		led->chip = chip;
>  		led->led_num = i;
> @@ -384,6 +374,15 @@ static int st1202_probe(struct i2c_client *client)
>  		if (ret < 0)
>  			return dev_err_probe(&client->dev, ret,
>  					"Failed to clear LED pattern\n");
> +
> +		init_data.fwnode = led->fwnode;
> +		init_data.devicename = "st1202";
> +		init_data.default_label = ":";
> +
> +		ret = devm_led_classdev_register_ext(&client->dev, &led->led_cdev, &init_data);
> +		if (ret < 0)
> +			return dev_err_probe(&client->dev, ret,
> +					"Failed to register LED class device\n");
>  	}
>  
>  	return 0;
> -- 
> 2.48.1
> 

-- 
Lee Jones [李琼斯]