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

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Date:   Wed, 18 Dec 2019 21:25:51 +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] gpio: gpio-grgpio: fix possible sleep-in-atomic-context bugs in grgpio_remove()

The driver may sleep while holding a spinlock.
The function call path (from bottom to top) in Linux 4.19 is:

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, gpiochip_remove() and irq_domain_remove() are called
without holding the spinlock.

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

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/gpio/gpio-grgpio.c      | 5 ++++-
 sound/soc/sti/uniperif_player.c | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-grgpio.c b/drivers/gpio/gpio-grgpio.c
index 08234e64993a..60a2871c5ba7 100644
--- a/drivers/gpio/gpio-grgpio.c
+++ b/drivers/gpio/gpio-grgpio.c
@@ -448,13 +448,16 @@ static int grgpio_remove(struct platform_device *ofdev)
 		}
 	}
 
+	spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
+
 	gpiochip_remove(&priv->gc);
 
 	if (priv->domain)
 		irq_domain_remove(priv->domain);
 
 out:
-	spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
+	if (ret)
+		spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
 
 	return ret;
 }
diff --git a/sound/soc/sti/uniperif_player.c b/sound/soc/sti/uniperif_player.c
index 48ea915b24ba..62244e207679 100644
--- a/sound/soc/sti/uniperif_player.c
+++ b/sound/soc/sti/uniperif_player.c
@@ -601,13 +601,14 @@ static int uni_player_ctl_iec958_put(struct snd_kcontrol *kcontrol,
 	mutex_unlock(&player->ctrl_lock);
 
 	spin_lock_irqsave(&player->irq_lock, flags);
+	spin_unlock_irqrestore(&player->irq_lock, flags);
+
 	if (player->substream && player->substream->runtime)
 		uni_player_set_channel_status(player,
 					      player->substream->runtime);
 	else
 		uni_player_set_channel_status(player, NULL);
 
-	spin_unlock_irqrestore(&player->irq_lock, flags);
 	return 0;
 }
 
-- 
2.17.1