linux-kernel - [PATCH] iio: envelope-detector: fix use-after-free on device remove

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Date:   Sun, 10 Mar 2019 15:32:46 -0400
From:   Sven Van Asbroeck <thesven73@...il.com>
To:     Peter Rosin <peda@...ntia.se>, Jonathan Cameron <jic23@...nel.org>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iio: envelope-detector: fix use-after-free on device remove

This driver's remove path never explicitly cancels the
delayed work. So it is possible for the delayed work to
run after the core has freed the private structure
(struct envelope). This is a potential use-after-free.

Fix by adding a devm_add_action callback to the remove
path, called right after iio_device_unregister(), which
explicitly cancels the delayed work.

This issue was detected with the help of Coccinelle.

Signed-off-by: Sven Van Asbroeck <TheSven73@...il.com>
---
 drivers/iio/adc/envelope-detector.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/iio/adc/envelope-detector.c b/drivers/iio/adc/envelope-detector.c
index 2f2b563c1162..2f1c78b3ff44 100644
--- a/drivers/iio/adc/envelope-detector.c
+++ b/drivers/iio/adc/envelope-detector.c
@@ -321,6 +321,14 @@ static const struct iio_info envelope_detector_info = {
 	.read_raw = &envelope_detector_read_raw,
 };
 
+static void envelope_detector_stop_work(void *data)
+{
+	struct iio_dev *indio_dev = data;
+	struct envelope *env = iio_priv(indio_dev);
+
+	cancel_delayed_work_sync(&env->comp_timeout);
+}
+
 static int envelope_detector_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -395,6 +403,10 @@ static int envelope_detector_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = devm_add_action(dev, envelope_detector_stop_work, indio_dev);
+	if (ret)
+		return ret;
+
 	return devm_iio_device_register(dev, indio_dev);
 }
 
-- 
2.17.1