[PATCH] hwmon: (gpio-fan) fix use-after-free in alarm work

fan_alarm_irq_handler() queues fan_data->alarm_work, but nothing
cancels it.  fan_alarm_notify() dereferences fan_data and its hwmon
device.  On unbind, devres frees the interrupt, which only waits for
the handler itself, and then releases the hwmon device and fan_data,
so a pending fan_alarm_notify() can run after those frees.

Replace INIT_WORK() with devm_work_autocancel(), registered before
devm_request_irq().  The devres cleanup then frees the interrupt
first, so no new work can be queued, and cancels the work while
fan_data and the hwmon device are still alive.

This issue was found by an in-house static analysis tool.

Fixes: d6fe1360f42e ("hwmon: add generic GPIO fan driver")
Cc: [email protected]
Assisted-by: Codex:gpt-5.6
Signed-off-by: Fan Wu <[email protected]>
---
 drivers/hwmon/gpio-fan.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/gpio-fan.c b/drivers/hwmon/gpio-fan.c
index 084828e1e281..7f36e5f6f223 100644
--- a/drivers/hwmon/gpio-fan.c
+++ b/drivers/hwmon/gpio-fan.c
@@ -12,6 +12,7 @@
 #include <linux/slab.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
+#include <linux/devm-helpers.h>
 #include <linux/platform_device.h>
 #include <linux/err.h>
 #include <linux/kstrtox.h>
@@ -84,6 +85,7 @@ static DEVICE_ATTR_RO(fan1_alarm);
 static int fan_alarm_init(struct gpio_fan_data *fan_data)
 {
 	int alarm_irq;
+	int err;
 	struct device *dev = fan_data->dev;
 
 	/*
@@ -94,7 +96,11 @@ static int fan_alarm_init(struct gpio_fan_data *fan_data)
 	if (alarm_irq <= 0)
 		return 0;
 
-	INIT_WORK(&fan_data->alarm_work, fan_alarm_notify);
+	err = devm_work_autocancel(dev, &fan_data->alarm_work,
+				   fan_alarm_notify);
+	if (err)
+		return err;
+
 	irq_set_irq_type(alarm_irq, IRQ_TYPE_EDGE_BOTH);
 	return devm_request_irq(dev, alarm_irq, fan_alarm_irq_handler,
 				IRQF_SHARED, "GPIO fan alarm", fan_data);