linux-kernel - [RFT] media: dvb_frontend: Fix use-after-free in __dvb_frontend

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Date:   Tue, 24 Oct 2017 17:06:48 +0530
From:   Arvind Yadav <arvind.yadav.cs@...il.com>
To:     mchehab@...nel.org, max.kellermann@...il.com, shuah@...nel.org,
        yamada.masahiro@...ionext.com, sakari.ailus@...ux.intel.com,
        colin.king@...onical.com, andreyknvl@...gle.com,
        dvyukov@...gle.com, kcc@...gle.com
Cc:     linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        syzkaller@...glegroups.com
Subject: [RFT] media: dvb_frontend: Fix use-after-free in __dvb_frontend_free

Here, dvb_free_device will free dvb_device. dvb_frontend_invoke_release
is using  dvb_device after free.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@...il.com>
---
This bug report by Andrey Konovalov (usb/media/dtt200u: use-after-free
in __dvb_frontend_free).

 drivers/media/dvb-core/dvb_frontend.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index 2fcba16..7f1ef12 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -147,10 +147,10 @@ static void dvb_frontend_free(struct kref *ref)
 		container_of(ref, struct dvb_frontend, refcount);
 	struct dvb_frontend_private *fepriv = fe->frontend_priv;
 
-	dvb_free_device(fepriv->dvbdev);
-
 	dvb_frontend_invoke_release(fe, fe->ops.release);
 
+	dvb_free_device(fepriv->dvbdev);
+
 	kfree(fepriv);
 }
 
-- 
1.9.1