power: supply: wm97xx: Fix NULL pointer dereference in power_supply_changed()

[ Upstream commit 39fe0ea ]

In `probe()`, `request_irq()` is called before allocating/registering a
`power_supply` handle. If an interrupt is fired between the call to
`request_irq()` and `power_supply_register()`, the `power_supply` handle
will be used uninitialized in `power_supply_changed()` in
`wm97xx_bat_update()` (triggered from the interrupt handler). This will
lead to a `NULL` pointer dereference since

Fix this racy `NULL` pointer dereference by making sure the IRQ is
requested _after_ the registration of the `power_supply` handle. Since
the IRQ is the last thing requests in the `probe()` now, remove the
error path for freeing it. Instead add one for unregistering the
`power_supply` handle when IRQ request fails.

Fixes: 7c87942 ("wm97xx_battery: Use irq to detect charger state")
Signed-off-by: Waqar Hameed <waqar.hameed@axis.com>
Link: https://patch.msgid.link/97b55f0479a932eea7213844bf66f28a974e27a2.1766270196.git.waqar.hameed@axis.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: whame

drivers/power/supply/wm97xx_battery.c

@@ -178,12 +178,6 @@ static int wm97xx_bat_probe(struct platform_device *dev)
 				     "failed to get charge GPIO\n");
 	if (charge_gpiod) {
 		gpiod_set_consumer_name(charge_gpiod, "BATT CHRG");
-		ret = request_irq(gpiod_to_irq(charge_gpiod),
-				wm97xx_chrg_irq, 0,
-				"AC Detect", dev);
-		if (ret)
-			return dev_err_probe(&dev->dev, ret,
-					     "failed to request GPIO irq\n");
 		props++;	/* POWER_SUPPLY_PROP_STATUS */
 	}
 
@@ -199,10 +193,8 @@ static int wm97xx_bat_probe(struct platform_device *dev)
 		props++;	/* POWER_SUPPLY_PROP_VOLTAGE_MIN */
 
 	prop = kcalloc(props, sizeof(*prop), GFP_KERNEL);
-	if (!prop) {
-		ret = -ENOMEM;
-		goto err3;
-	}
+	if (!prop)
+		return -ENOMEM;
 
 	prop[i++] = POWER_SUPPLY_PROP_PRESENT;
 	if (charge_gpiod)
@@ -236,15 +228,27 @@ static int wm97xx_bat_probe(struct platform_device *dev)
 		schedule_work(&bat_work);
 	} else {
 		ret = PTR_ERR(bat_psy);
-		goto err4;
+		goto free;
+	}
+
+	if (charge_gpiod) {
+		ret = request_irq(gpiod_to_irq(charge_gpiod), wm97xx_chrg_irq,
+				  0, "AC Detect", dev);
+		if (ret) {
+			dev_err_probe(&dev->dev, ret,
+				      "failed to request GPIO irq\n");
+			goto unregister;
+		}
 	}
 
 	return 0;
-err4:
+
+unregister:
+	power_supply_unregister(bat_psy);
+
+free:
 	kfree(prop);
-err3:
-	if (charge_gpiod)
-		free_irq(gpiod_to_irq(charge_gpiod), dev);
+
 	return ret;
 }