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From:   Johan Hovold <johan@kernel.org>
To:     Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Saravana Kannan <saravanak@google.com>,
        linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
        Johan Hovold <johan@kernel.org>, stable@vger.kernel.org
Subject: [PATCH v2 2/2] gpio: fix gpio-device list corruption
Date:   Mon,  1 Mar 2021 10:05:19 +0100
Message-Id: <20210301090519.26192-3-johan@kernel.org>
In-Reply-To: <20210301090519.26192-1-johan@kernel.org>
References: <20210301090519.26192-1-johan@kernel.org>
MIME-Version: 1.0
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Precedence: bulk

Make sure to hold the gpio_lock when removing the gpio device from the
gpio_devices list (when dropping the last reference) to avoid corrupting
the list when there are concurrent accesses.

Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
Cc: stable@vger.kernel.org      # 4.6
Reviewed-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/gpio/gpiolib.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 6e0572515d02..4253837f870b 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -475,8 +475,12 @@ EXPORT_SYMBOL_GPL(gpiochip_line_is_valid);
 static void gpiodevice_release(struct device *dev)
 {
 	struct gpio_device *gdev = container_of(dev, struct gpio_device, dev);
+	unsigned long flags;
 
+	spin_lock_irqsave(&gpio_lock, flags);
 	list_del(&gdev->list);
+	spin_unlock_irqrestore(&gpio_lock, flags);
+
 	ida_free(&gpio_ida, gdev->id);
 	kfree_const(gdev->label);
 	kfree(gdev->descs);
-- 
2.26.2