[PATCH] hwmon: (lm90) Only report alarms if driver is ready

Userspace can read sysfs attributes before driver registration is complete,
immediately after devm_hwmon_device_register_with_info() has been called.
At that time, data->hwmon_dev is not yet initialized. This can trigger
a NULL pointer access since lm90_update_device() and with it
lm90_update_alarms_locked() will be called. This call schedules
report_work and lm90_report_alarms(), which passes the still-NULL
data->hwmon_dev to hwmon_notify_event() and triggers a NULL pointer
dereference.

Fix the problem by only scheduling the worker if data->hwmon_dev is set.

Reported-by: Sashiko <[email protected]>
Fixes: f6d0775119fb9 ("hwmon: (lm90) Rework alarm/status handling")
Signed-off-by: Guenter Roeck <[email protected]>
---
 drivers/hwmon/lm90.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
index 4b9c0ccdf260..b03f75f4ddec 100644
--- a/drivers/hwmon/lm90.c
+++ b/drivers/hwmon/lm90.c
@@ -1194,7 +1194,7 @@ static int lm90_update_alarms_locked(struct lm90_data *data, bool force)
 		check_enable = (client->irq || !(data->config_orig & 0x80)) &&
 			(data->config & 0x80);
 
-		if (force || check_enable)
+		if (data->hwmon_dev && (force || check_enable))
 			schedule_work(&data->report_work);
 
 		/*
-- 
2.45.2