power: supply: act8945a: 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: a09209acd6a8 ("power: supply: act8945a_charger: Add status change update support")
Signed-off-by: Waqar Hameed <waqar.hameed@axis.com>
Link: https://patch.msgid.link/bcf3a23b5187df0bba54a8c8fe09f8b8a0031dee.1766268280.git.waqar.hameed@axis.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

diff --git a/drivers/power/supply/act8945a_charger.c b/drivers/power/supply/act8945a_charger.c
index 3901a02f326a55f820e85346ebe0420ac9a6f113..9dec4486b1439aa9b3a919385f5458d2372973a2 100644 (file)
--- a/drivers/power/supply/act8945a_charger.c
+++ b/drivers/power/supply/act8945a_charger.c
@@ -597,14 +597,6 @@ static int act8945a_charger_probe(struct platform_device *pdev)
                return irq ?: -ENXIO;
        }
 
-       ret = devm_request_irq(&pdev->dev, irq, act8945a_status_changed,
-                              IRQF_TRIGGER_FALLING, "act8945a_interrupt",
-                              charger);
-       if (ret) {
-               dev_err(&pdev->dev, "failed to request nIRQ pin IRQ\n");
-               return ret;
-       }
-
        charger->desc.name = "act8945a-charger";
        charger->desc.get_property = act8945a_charger_get_property;
        charger->desc.properties = act8945a_charger_props;
@@ -625,6 +617,14 @@ static int act8945a_charger_probe(struct platform_device *pdev)
                return PTR_ERR(charger->psy);
        }
 
+       ret = devm_request_irq(&pdev->dev, irq, act8945a_status_changed,
+                              IRQF_TRIGGER_FALLING, "act8945a_interrupt",
+                              charger);
+       if (ret) {
+               dev_err(&pdev->dev, "failed to request nIRQ pin IRQ\n");
+               return ret;
+       }
+
        platform_set_drvdata(pdev, charger);
 
        INIT_WORK(&charger->work, act8945a_work);