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

[ Upstream commit b2ce982 ]

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: 84d7b76 ("power: Add battery driver for goldfish emulator")
Signed-off-by: Waqar Hameed <waqar.hameed@axis.com>
Link: https://patch.msgid.link/500a606bb6fb6f2bb8d797e19a00cea9dd7b03c1.1766268280.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/goldfish_battery.c

@@ -224,12 +224,6 @@ static int goldfish_battery_probe(struct platform_device *pdev)
 	if (data->irq < 0)
 		return -ENODEV;
 
-	ret = devm_request_irq(&pdev->dev, data->irq,
-			       goldfish_battery_interrupt,
-			       IRQF_SHARED, pdev->name, data);
-	if (ret)
-		return ret;
-
 	psy_cfg.drv_data = data;
 
 	data->ac = devm_power_supply_register(&pdev->dev,
@@ -244,6 +238,12 @@ static int goldfish_battery_probe(struct platform_device *pdev)
 	if (IS_ERR(data->battery))
 		return PTR_ERR(data->battery);
 
+	ret = devm_request_irq(&pdev->dev, data->irq,
+			       goldfish_battery_interrupt,
+			       IRQF_SHARED, pdev->name, data);
+	if (ret)
+		return ret;
+
 	GOLDFISH_BATTERY_WRITE(data, BATTERY_INT_ENABLE, BATTERY_INT_MASK);
 	return 0;
 }