linux-kernel - [PATCH 5/6] drivers/media/media-device: add "release" callback

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Date:	Mon, 21 Mar 2016 14:30:38 +0100
From:	Max Kellermann <max@...mpel.org>
To:	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: [PATCH 5/6] drivers/media/media-device: add "release" callback

Allow the client to free its data structures only after all files have
been closed (fixing use-after-free bugs).

Signed-off-by: Max Kellermann <max@...mpel.org>
---
 drivers/media/media-device.c |    9 +++++++--
 include/media/media-device.h |    2 ++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
index 5c4669c..a3901f9 100644
--- a/drivers/media/media-device.c
+++ b/drivers/media/media-device.c
@@ -551,9 +551,14 @@ static DEVICE_ATTR(model, S_IRUGO, show_model, NULL);
  * Registration/unregistration
  */
 
-static void media_device_release(struct media_devnode *mdev)
+static void media_device_release(struct media_devnode *devnode)
 {
-	dev_dbg(mdev->parent, "Media device released\n");
+	struct media_device *mdev = to_media_device(devnode);
+
+	dev_dbg(devnode->parent, "Media device released\n");
+
+	if (mdev->release)
+		mdev->release(mdev);
 }
 
 /**
diff --git a/include/media/media-device.h b/include/media/media-device.h
index d385589..d184d0c 100644
--- a/include/media/media-device.h
+++ b/include/media/media-device.h
@@ -326,6 +326,8 @@ struct media_device {
 
 	int (*link_notify)(struct media_link *link, u32 flags,
 			   unsigned int notification);
+
+	void (*release)(struct media_device *mdev);
 };
 
 #ifdef CONFIG_MEDIA_CONTROLLER