linux-kernel - [PATCH 5.6 23/23] media: v4l2-core: fix a use-after-free bug of sd->devnode

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Date:   Tue, 31 Mar 2020 10:59:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Dafna Hirschfeld <dafna.hirschfeld@...labora.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Subject: [PATCH 5.6 23/23] media: v4l2-core: fix a use-after-free bug of sd->devnode

From: Dafna Hirschfeld <dafna.hirschfeld@...labora.com>

commit 6990570f7e0a6078e11b9c5dc13f4b6e3f49a398 upstream.

sd->devnode is released after calling
v4l2_subdev_release. Therefore it should be set
to NULL so that the subdev won't hold a pointer
to a released object. This fixes a reference
after free bug in function
v4l2_device_unregister_subdev

Fixes: 0e43734d4c46e ("media: v4l2-subdev: add release() internal op")

Cc: stable@...r.kernel.org
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@...labora.com>
Reviewed-by: Ezequiel Garcia <ezequiel@...labora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/media/v4l2-core/v4l2-device.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/media/v4l2-core/v4l2-device.c
+++ b/drivers/media/v4l2-core/v4l2-device.c
@@ -179,6 +179,7 @@ static void v4l2_subdev_release(struct v
 
 	if (sd->internal_ops && sd->internal_ops->release)
 		sd->internal_ops->release(sd);
+	sd->devnode = NULL;
 	module_put(owner);
 }