power: supply: rt9455: Fix use-after-free in power_supply_changed()

[ Upstream commit e2febe3 ]

Using the `devm_` variant for requesting IRQ _before_ the `devm_`
variant for allocating/registering the `power_supply` handle, means that
the `power_supply` handle will be deallocated/unregistered _before_ the
interrupt handler (since `devm_` naturally deallocates in reverse
allocation order). This means that during removal, there is a race
condition where an interrupt can fire just _after_ the `power_supply`
handle has been freed, *but* just _before_ the corresponding
unregistration of the IRQ handler has run.

This will lead to the IRQ handler calling `power_supply_changed()` with
a freed `power_supply` handle. Which usually crashes the system or
otherwise silently corrupts the memory...

Note that there is a similar situation which can also happen during
`probe()`; the possibility of an interrupt firing _before_ registering
the `power_supply` handle. This would then lead to the nasty situation
of using the `power_supply` handle *uninitialized* in
`power_supply_changed()`.

Fix this racy use-after-free by making sure the IRQ is requested _after_
the registration of the `power_supply` handle.

Fixes: e86d69d ("power_supply: Add support for Richtek RT9455 battery charger")
Signed-off-by: Waqar Hameed <waqar.hameed@axis.com>
Link: https://patch.msgid.link/1567d831e04c3e2fcb9e18dd36b7bcba4634581a.1766268280.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/rt9455_charger.c

@@ -1663,6 +1663,15 @@ static int rt9455_probe(struct i2c_client *client)
 	rt9455_charger_config.supplied_to	= rt9455_charger_supplied_to;
 	rt9455_charger_config.num_supplicants	=
 					ARRAY_SIZE(rt9455_charger_supplied_to);
+
+	info->charger = devm_power_supply_register(dev, &rt9455_charger_desc,
+						   &rt9455_charger_config);
+	if (IS_ERR(info->charger)) {
+		dev_err(dev, "Failed to register charger\n");
+		ret = PTR_ERR(info->charger);
+		goto put_usb_notifier;
+	}
+
 	ret = devm_request_threaded_irq(dev, client->irq, NULL,
 					rt9455_irq_handler_thread,
 					IRQF_TRIGGER_LOW | IRQF_ONESHOT,
@@ -1678,14 +1687,6 @@ static int rt9455_probe(struct i2c_client *client)
 		goto put_usb_notifier;
 	}
 
-	info->charger = devm_power_supply_register(dev, &rt9455_charger_desc,
-						   &rt9455_charger_config);
-	if (IS_ERR(info->charger)) {
-		dev_err(dev, "Failed to register charger\n");
-		ret = PTR_ERR(info->charger);
-		goto put_usb_notifier;
-	}
-
 	return 0;
 
 put_usb_notifier: