[PATCH 2/4] gpio: mt7621: more robust management of IRQ domain teardown

[Sergio Paracuellos]

The driver uses devm_gpiochip_add_data() to register the GPIO chips which
means the devres subsystem will unregister them only after the function
'mt7621_gpio_remove()' returns. During the window between domain destruction
and devres unregistering the GPIO chips, the chips are still fully active.
If a consumer or userspace invokes gpiod_to_irq() during this window,
'mt7621_gpio_to_irq()' can dereference the already-freed irq domain pointer.
Thus, manage the IRQ domain teardown using 'devm_add_action_or_reset()' to
guarantee it is destroyed strictly after the GPIO chips are removed.

Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@xxxxxxxxx>
---
 drivers/gpio/gpio-mt7621.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/gpio/gpio-mt7621.c b/drivers/gpio/gpio-mt7621.c
index ceb99641baee..57384ef74703 100644
--- a/drivers/gpio/gpio-mt7621.c
+++ b/drivers/gpio/gpio-mt7621.c
@@ -272,9 +272,9 @@ static const struct irq_chip mt7621_irq_chip = {
 };
 
 static void
-mt7621_gpio_remove(struct platform_device *pdev)
+mt7621_gpio_remove(void *data)
 {
-	struct mtk *priv = platform_get_drvdata(pdev);
+	struct mtk *priv = data;
 	int offset, virq;
 
 	if (priv->gpio_irq > 0)
@@ -475,14 +475,14 @@ mediatek_gpio_probe(struct platform_device *pdev)
 	if (mtk->gpio_irq > 0) {
 		ret = mt7621_gpio_irq_setup(pdev, mtk);
 		if (ret)
-			goto fail;
+			return ret;
 	}
 
-	return 0;
+	ret = devm_add_action_or_reset(dev, mt7621_gpio_remove, mtk);
+	if (ret)
+		return ret;
 
-fail:
-	mt7621_gpio_remove(pdev);
-	return ret;
+	return 0;
 }
 
 static const struct of_device_id mediatek_gpio_match[] = {
@@ -493,7 +493,6 @@ MODULE_DEVICE_TABLE(of, mediatek_gpio_match);
 
 static struct platform_driver mediatek_gpio_driver = {
 	.probe = mediatek_gpio_probe,
-	.remove = mt7621_gpio_remove,
 	.driver = {
 		.name = "mt7621_gpio",
 		.of_match_table = mediatek_gpio_match,
-- 
2.43.0