power: supply: ab8500: 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()`.

Commit 1c1f13a ("power: supply: ab8500: Move to componentized
binding") introduced this issue during a refactorization. Fix this racy
use-after-free by making sure the IRQ is requested _after_ the
registration of the `power_supply` handle.

Fixes: 1c1f13a ("power: supply: ab8500: Move to componentized binding")
Signed-off-by: Waqar Hameed <waqar.hameed@axis.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/ccf83a09942cb8dda3dff70b2682f2c2e9cb97f2.1766268280.git.waqar.hameed@axis.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Author: whame

drivers/power/supply/ab8500_charger.c

@@ -3466,26 +3466,6 @@ static int ab8500_charger_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	/* Request interrupts */
-	for (i = 0; i < ARRAY_SIZE(ab8500_charger_irq); i++) {
-		irq = platform_get_irq_byname(pdev, ab8500_charger_irq[i].name);
-		if (irq < 0)
-			return irq;
-
-		ret = devm_request_threaded_irq(dev,
-			irq, NULL, ab8500_charger_irq[i].isr,
-			IRQF_SHARED | IRQF_NO_SUSPEND | IRQF_ONESHOT,
-			ab8500_charger_irq[i].name, di);
-
-		if (ret != 0) {
-			dev_err(dev, "failed to request %s IRQ %d: %d\n"
-				, ab8500_charger_irq[i].name, irq, ret);
-			return ret;
-		}
-		dev_dbg(dev, "Requested %s IRQ %d: %d\n",
-			ab8500_charger_irq[i].name, irq, ret);
-	}
-
 	/* initialize lock */
 	spin_lock_init(&di->usb_state.usb_lock);
 	mutex_init(&di->usb_ipt_crnt_lock);
@@ -3614,6 +3594,26 @@ static int ab8500_charger_probe(struct platform_device *pdev)
 		return PTR_ERR(di->usb_chg.psy);
 	}
 
+	/* Request interrupts */
+	for (i = 0; i < ARRAY_SIZE(ab8500_charger_irq); i++) {
+		irq = platform_get_irq_byname(pdev, ab8500_charger_irq[i].name);
+		if (irq < 0)
+			return irq;
+
+		ret = devm_request_threaded_irq(dev,
+			irq, NULL, ab8500_charger_irq[i].isr,
+			IRQF_SHARED | IRQF_NO_SUSPEND | IRQF_ONESHOT,
+			ab8500_charger_irq[i].name, di);
+
+		if (ret != 0) {
+			dev_err(dev, "failed to request %s IRQ %d: %d\n"
+				, ab8500_charger_irq[i].name, irq, ret);
+			return ret;
+		}
+		dev_dbg(dev, "Requested %s IRQ %d: %d\n",
+			ab8500_charger_irq[i].name, irq, ret);
+	}
+
 	/*
 	 * Check what battery we have, since we always have the USB
 	 * psy, use that as a handle.