linux-kernel - [PATCH 06/11] power: supply: goldfish: Fix use-after-free in power_supply

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Message-ID: <500a606bb6fb6f2bb8d797e19a00cea9dd7b03c1.1766268280.git.waqar.hameed@axis.com>
Date: Sat, 20 Dec 2025 23:36:00 +0100
From: Waqar Hameed <waqar.hameed@...s.com>
To: Sebastian Reichel <sre@...nel.org>, "Mike A. Chan" <mikechan@...gle.com>,
	Alan Cox <alan@...ux.intel.com>, Tom Keel <thomas.keel@...el.com>, "Yunhong
 Jiang" <yunhong.jiang@...el.com>, Sheng Yang <sheng@...ux.intel.com>
CC: <kernel@...s.com>, Bruce Beare <bruce.j.beare@...el.com>, Anton Vorontsov
	<anton@...msg.org>, Jun Nakajima <jun.nakajima@...el.com>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 06/11] 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@...s.com>
---
 drivers/power/supply/goldfish_battery.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/power/supply/goldfish_battery.c b/drivers/power/supply/goldfish_battery.c
index 479195e35d734..5aa24e4dc4455 100644
--- 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;
 }
-- 
2.39.5