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

Manuel Fombuena
2025-02-01T13:03:00Z

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.

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