[PATCH 1/2] hwmon: (lm90) Stop work before releasing hwmon device

[Guenter Roeck <linux@roeck-us.net>]

Sashiko reports:

In lm90_probe(), the devm action to cancel the alert_work and report_work
(lm90_restore_conf) is registered in lm90_init_client() before
devm_hwmon_device_register_with_info() is called.

Because devm executes cleanup actions in reverse order during module
unbind or probe failure, the hwmon device is unregistered and freed first.

If lm90_alert_work() or lm90_report_alarms() runs in the window between
the hwmon device being freed and the delayed works being cancelled,
lm90_update_alarms() will dereference the freed data->hwmon_dev here.

Fix the problem by canceling the workers separately after registering
the hwmon device and before registering the interrupt handler. This ensures
that the workers are canceled after interrupts are disabled and before
the hwmon device is released.

Fixes: f6d0775119fb9 ("hwmon: (lm90) Rework alarm/status handling")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/lm90.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
index 3c10a5066b53..50b30d719225 100644
--- a/drivers/hwmon/lm90.c
+++ b/drivers/hwmon/lm90.c
@@ -2584,15 +2584,20 @@ static void lm90_restore_conf(void *_data)
 	struct lm90_data *data = _data;
 	struct i2c_client *client = data->client;
 
-	cancel_delayed_work_sync(&data->alert_work);
-	cancel_work_sync(&data->report_work);
-
 	/* Restore initial configuration */
 	if (data->flags & LM90_HAVE_CONVRATE)
 		lm90_write_convrate(data, data->convrate_orig);
 	lm90_write_reg(client, LM90_REG_CONFIG1, data->config_orig);
 }
 
+static void lm90_stop_work(void *_data)
+{
+	struct lm90_data *data = _data;
+
+	cancel_delayed_work_sync(&data->alert_work);
+	cancel_work_sync(&data->report_work);
+}
+
 static int lm90_init_client(struct i2c_client *client, struct lm90_data *data)
 {
 	struct device_node *np = client->dev.of_node;
@@ -2902,6 +2907,10 @@ static int lm90_probe(struct i2c_client *client)
 
 	data->hwmon_dev = hwmon_dev;
 
+	err = devm_add_action_or_reset(&client->dev, lm90_stop_work, data);
+	if (err)
+		return err;
+
 	if (client->irq) {
 		dev_dbg(dev, "IRQ: %d\n", client->irq);
 		err = devm_request_threaded_irq(dev, client->irq,
-- 
2.45.2