linux-kernel - [PATCH 3/3] drivers/media/media-device: fix double free bug in

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Date:	Wed, 15 Jun 2016 22:15:12 +0200
From:	Max Kellermann <max@...mpel.org>
To:	linux-media@...r.kernel.org, shuahkh@....samsung.com,
	mchehab@....samsung.com
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] drivers/media/media-device: fix double free bug in
 _unregister()

While removing all interfaces in media_device_unregister(), all
media_interface pointers are freed.  This is illegal and results in
double kfree() if any media_interface is still linked at this point;
maybe because a userspace process still has a file handle.  Once the
process closes the file handle, dvb_media_device_free() gets called,
which frees the dvb_device.intf_devnode again.

This patch removes the unnecessary kfree() call, and documents who's
responsible for really freeing it.

Signed-off-by: Max Kellermann <max@...mpel.org>
---
 drivers/media/media-device.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
index 33a9952..1db4707 100644
--- a/drivers/media/media-device.c
+++ b/drivers/media/media-device.c
@@ -799,9 +799,11 @@ void media_device_unregister(struct media_device *mdev)
 	/* Remove all interfaces from the media device */
 	list_for_each_entry_safe(intf, tmp_intf, &mdev->interfaces,
 				 graph_obj.list) {
+		/* unlink the interface, but don't free it here; the
+		   module which created it is responsible for freeing
+		   it */
 		__media_remove_intf_links(intf);
 		media_gobj_destroy(&intf->graph_obj);
-		kfree(intf);
 	}

 	mutex_unlock(&mdev->graph_mutex);