linux-kernel - [PATCH 03/11] power: supply: bq256xx: Fix use-after-free in power_supply

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Message-ID: <39da6da8cc060fa0382ca859f65071e791cb6119.1766268280.git.waqar.hameed@axis.com>
Date: Sat, 20 Dec 2025 23:35:59 +0100
From: Waqar Hameed <waqar.hameed@...s.com>
To: Sebastian Reichel <sre@...nel.org>, Ricardo Rivera-Matos
	<r-rivera-matos@...com>
CC: <kernel@...s.com>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 03/11] power: supply: bq256xx: 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: 32e4978bb920 ("power: supply: bq256xx: Introduce the BQ256XX charger driver")
Signed-off-by: Waqar Hameed <waqar.hameed@...s.com>
---
 drivers/power/supply/bq256xx_charger.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/power/supply/bq256xx_charger.c b/drivers/power/supply/bq256xx_charger.c
index ae14162f017a9..d3de4f8b80db1 100644
--- a/drivers/power/supply/bq256xx_charger.c
+++ b/drivers/power/supply/bq256xx_charger.c
@@ -1741,6 +1741,12 @@ static int bq256xx_probe(struct i2c_client *client)
 		usb_register_notifier(bq->usb3_phy, &bq->usb_nb);
 	}

+	ret = bq256xx_power_supply_init(bq, &psy_cfg, dev);
+	if (ret) {
+		dev_err(dev, "Failed to register power supply\n");
+		return ret;
+	}
+
 	if (client->irq) {
 		ret = devm_request_threaded_irq(dev, client->irq, NULL,
 						bq256xx_irq_handler_thread,
@@ -1753,12 +1759,6 @@ static int bq256xx_probe(struct i2c_client *client)
 		}
 	}

-	ret = bq256xx_power_supply_init(bq, &psy_cfg, dev);
-	if (ret) {
-		dev_err(dev, "Failed to register power supply\n");
-		return ret;
-	}
-
 	ret = bq256xx_hw_init(bq);
 	if (ret) {
 		dev_err(dev, "Cannot initialize the chip.\n");
-- 
2.39.5