power: supply: act8945a: Fix use-after-free in power_supply_changed()

[ Upstream commit 3291c51 ]

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: a09209a ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: whame

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);