linux-kernel - [PATCH AUTOSEL 4.20 064/304] media: video-i2c: avoid accessing released memory area when removing driver

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Message-Id: <20190128154341.47195-64-sashal@kernel.org>
Date:   Mon, 28 Jan 2019 10:39:41 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Akinobu Mita <akinobu.mita@...il.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-media@...r.kernel.org
Subject: [PATCH AUTOSEL 4.20 064/304] media: video-i2c: avoid accessing released memory area when removing driver

From: Akinobu Mita <akinobu.mita@...il.com>

[ Upstream commit c764da98a600a4b068d25c77164f092f159cecec ]

The video device release() callback for video-i2c driver frees the whole
struct video_i2c_data.  If there is no user left for the video device
when video_unregister_device() is called, the release callback is executed.

However, in video_i2c_remove() some fields (v4l2_dev, lock, and queue_lock)
in struct video_i2c_data are still accessed after video_unregister_device()
is called.

This fixes the use after free by moving the code from video_i2c_remove()
to the release() callback.

Fixes: 5cebaac60974 ("media: video-i2c: add video-i2c driver")

Reviewed-by: Matt Ranostay <matt.ranostay@...sulko.com>
Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
Acked-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/i2c/video-i2c.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/media/i2c/video-i2c.c b/drivers/media/i2c/video-i2c.c
index 4d49af86c15e..ec0758dca2fc 100644
--- a/drivers/media/i2c/video-i2c.c
+++ b/drivers/media/i2c/video-i2c.c
@@ -510,7 +510,12 @@ static const struct v4l2_ioctl_ops video_i2c_ioctl_ops = {
 
 static void video_i2c_release(struct video_device *vdev)
 {
-	kfree(video_get_drvdata(vdev));
+	struct video_i2c_data *data = video_get_drvdata(vdev);
+
+	v4l2_device_unregister(&data->v4l2_dev);
+	mutex_destroy(&data->lock);
+	mutex_destroy(&data->queue_lock);
+	kfree(data);
 }
 
 static int video_i2c_probe(struct i2c_client *client,
@@ -608,10 +613,6 @@ static int video_i2c_remove(struct i2c_client *client)
 	struct video_i2c_data *data = i2c_get_clientdata(client);
 
 	video_unregister_device(&data->vdev);
-	v4l2_device_unregister(&data->v4l2_dev);
-
-	mutex_destroy(&data->lock);
-	mutex_destroy(&data->queue_lock);
 
 	return 0;
 }
-- 
2.19.1