[PATCH 1/2] power: supply: max14656: fix potential use-before-alloc

[PATCH 1/2] power: supply: max14656: fix potential use-before-alloc

[Sven Van Asbroeck]

Call order on probe():
- max14656_hw_init() enables interrupts on the chip
- devm_request_irq() starts processing interrupts, isr
  could be called immediately
-    isr: schedules delayed work (irq_work)
-    irq_work: calls power_supply_changed()
- devm_power_supply_register() registers the power supply

Depending on timing, it's possible that power_supply_changed()
is called on an unregistered power supply structure.

Fix by registering the power supply before requesting the irq.

Cc: Alexander Kurz <akurz@blala.de>
Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
---
 drivers/power/supply/max14656_charger_detector.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/power/supply/max14656_charger_detector.c b/drivers/power/supply/max14656_charger_detector.c
index b91b1d2999dc..d19307f791c6 100644
--- a/drivers/power/supply/max14656_charger_detector.c
+++ b/drivers/power/supply/max14656_charger_detector.c
@@ -280,6 +280,13 @@ static int max14656_probe(struct i2c_client *client,
 
 	INIT_DELAYED_WORK(&chip->irq_work, max14656_irq_worker);
 
+	chip->detect_psy = devm_power_supply_register(dev,
+		       &chip->psy_desc, &psy_cfg);
+	if (IS_ERR(chip->detect_psy)) {
+		dev_err(dev, "power_supply_register failed\n");
+		return -EINVAL;
+	}
+
 	ret = devm_request_irq(dev, chip->irq, max14656_irq,
 			       IRQF_TRIGGER_FALLING,
 			       MAX14656_NAME, chip);
@@ -289,13 +296,6 @@ static int max14656_probe(struct i2c_client *client,
 	}
 	enable_irq_wake(chip->irq);
 
-	chip->detect_psy = devm_power_supply_register(dev,
-		       &chip->psy_desc, &psy_cfg);
-	if (IS_ERR(chip->detect_psy)) {
-		dev_err(dev, "power_supply_register failed\n");
-		return -EINVAL;
-	}
-
 	schedule_delayed_work(&chip->irq_work, msecs_to_jiffies(2000));
 
 	return 0;
-- 
2.17.1

[PATCH 2/2] power: supply: max14656: fix potential use-after-free

[Sven Van Asbroeck]

Explicitly cancel/sync the irq_work delayed work, otherwise
there's a chance that it will run after the device is removed,
which would result in a use-after-free.

Note that cancel/sync should happen:
- after irq's have been disabled, as the isr re-schedules the work
- before the power supply is unregistered, because the work func
    uses the power supply handle.

Cc: Alexander Kurz <akurz@blala.de>
Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
---
 .../power/supply/max14656_charger_detector.c    | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/power/supply/max14656_charger_detector.c b/drivers/power/supply/max14656_charger_detector.c
index d19307f791c6..9e6472834e37 100644
--- a/drivers/power/supply/max14656_charger_detector.c
+++ b/drivers/power/supply/max14656_charger_detector.c
@@ -240,6 +240,14 @@ static enum power_supply_property max14656_battery_props[] = {
 	POWER_SUPPLY_PROP_MANUFACTURER,
 };
 
+static void stop_irq_work(void *data)
+{
+	struct max14656_chip *chip = data;
+
+	cancel_delayed_work_sync(&chip->irq_work);
+}
+
+
 static int max14656_probe(struct i2c_client *client,
 			  const struct i2c_device_id *id)
 {
@@ -278,8 +286,6 @@ static int max14656_probe(struct i2c_client *client,
 	if (ret)
 		return -ENODEV;
 
-	INIT_DELAYED_WORK(&chip->irq_work, max14656_irq_worker);
-
 	chip->detect_psy = devm_power_supply_register(dev,
 		       &chip->psy_desc, &psy_cfg);
 	if (IS_ERR(chip->detect_psy)) {
@@ -287,6 +293,13 @@ static int max14656_probe(struct i2c_client *client,
 		return -EINVAL;
 	}
 
+	INIT_DELAYED_WORK(&chip->irq_work, max14656_irq_worker);
+	ret = devm_add_action(dev, stop_irq_work, chip);
+	if (ret) {
+		dev_err(dev, "devm_add_action %d failed\n", ret);
+		return ret;
+	}
+
 	ret = devm_request_irq(dev, chip->irq, max14656_irq,
 			       IRQF_TRIGGER_FALLING,
 			       MAX14656_NAME, chip);
-- 
2.17.1