[PATCH 26/28] mfd: mt6397: Unregister PM notifier on probe failure and unbind

[Lee Jones]

mt6397_irq_init() registers a power management notifier block embedded
in the devres-managed struct mt6397_chip via register_pm_notifier(),
but never unregisters it if mt6397_probe() later fails or when the
driver is unbound.  Once devres frees struct mt6397_chip, the dangling
notifier block corrupts the global PM notifier chain and causes a
use-after-free on subsequent suspend or resume transitions.

Check the return value of register_pm_notifier() and register a devres
action to unregister the PM notifier on probe failure or device unbind.

Fixes: 4e2e7cfec13a ("mfd: mt6397: Modify suspend/resume behavior")
Closes: https://sashiko.dev/#/bug/linux-edb62fbc-213a-49a2-be55-c002e234e554
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
---
 drivers/mfd/mt6397-irq.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/mt6397-irq.c b/drivers/mfd/mt6397-irq.c
index 58645dbd8095..bc7ca22d6f17 100644
--- a/drivers/mfd/mt6397-irq.c
+++ b/drivers/mfd/mt6397-irq.c
@@ -179,6 +179,13 @@ static void mt6397_irq_domain_remove(void *data)
 	irq_domain_remove(chip->irq_domain);
 }
 
+static void mt6397_unregister_pm_notifier(void *data)
+{
+	struct mt6397_chip *chip = data;
+
+	unregister_pm_notifier(&chip->pm_nb);
+}
+
 int mt6397_irq_init(struct mt6397_chip *chip)
 {
 	int ret;
@@ -247,6 +254,10 @@ int mt6397_irq_init(struct mt6397_chip *chip)
 		return ret;
 	}
 
-	register_pm_notifier(&chip->pm_nb);
-	return 0;
+	ret = register_pm_notifier(&chip->pm_nb);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(chip->dev,
+					mt6397_unregister_pm_notifier, chip);
 }
-- 
2.56.0.218.g1ec904b173-goog