linux-kernel - [PATCH 1/2 v2] gpio: gpio-grgpio: fix possible sleep-in-atomic-context bugs in grgpio

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Message-Id: <20191219131459.18640-1-baijiaju1990@gmail.com>
Date:   Thu, 19 Dec 2019 21:14:59 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     linus.walleij@...aro.org, bgolaszewski@...libre.com
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH 1/2 v2] gpio: gpio-grgpio: fix possible sleep-in-atomic-context bugs in grgpio_remove()

drivers/gpio/gpiolib-sysfs.c, 796:
	mutex_lock in gpiochip_sysfs_unregister
drivers/gpio/gpiolib.c, 1455:
	gpiochip_sysfs_unregister in gpiochip_remove
drivers/gpio/gpio-grgpio.c, 460:
	gpiochip_remove in grgpio_remove
drivers/gpio/gpio-grgpio.c, 449:
	_raw_spin_lock_irqsave in grgpio_remove

kernel/irq/irqdomain.c, 243:
	mutex_lock in irq_domain_remove
drivers/gpio/gpio-grgpio.c, 463:
	irq_domain_remove in grgpio_remove
drivers/gpio/gpio-grgpio.c, 449:
	_raw_spin_lock_irqsave in grgpio_remove

mutex_lock() can sleep at runtime.

To fix these bugs, the lock is dropped in grgpio_remove(), because there
is no need for locking in remove() callbacks.

These bugs are found by a static analysis tool STCheck written by
myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
v2:
* Drop the lock instead of moving the calls to lock functions.
  Thank Bartosz for good advice.

---
 drivers/gpio/gpio-grgpio.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/gpio/gpio-grgpio.c b/drivers/gpio/gpio-grgpio.c
index 08234e64993a..a49f0711ca94 100644
--- a/drivers/gpio/gpio-grgpio.c
+++ b/drivers/gpio/gpio-grgpio.c
@@ -437,8 +437,6 @@ static int grgpio_remove(struct platform_device *ofdev)
 	int i;
 	int ret = 0;
 
-	spin_lock_irqsave(&priv->gc.bgpio_lock, flags);
-
 	if (priv->domain) {
 		for (i = 0; i < GRGPIO_MAX_NGPIO; i++) {
 			if (priv->uirqs[i].refcnt != 0) {
@@ -454,8 +452,6 @@ static int grgpio_remove(struct platform_device *ofdev)
 		irq_domain_remove(priv->domain);
 
 out:
-	spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
-
 	return ret;
 }
 
-- 
2.17.1