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

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: 84d7b7687489 ("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>

diff --git a/drivers/power/supply/goldfish_battery.c b/drivers/power/supply/goldfish_battery.c
index 479195e35d734aa44c0eaa7164c6a0afb82e8064..5aa24e4dc4455de09b7d25dc608ca4af4505da6e 100644 (file)
--- a/drivers/power/supply/goldfish_battery.c
+++ b/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;
 }