linux-kernel - [PATCH] media: dvb-core: Fix double free in dvb_register

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Date:   Tue, 26 Apr 2022 05:29:19 +0000
From:   Keita Suzuki <keitasuzuki.park@...ab.ics.keio.ac.jp>
To:     unlisted-recipients:; (no To-header on input)
Cc:     kernel@...force.de, wanghai38@...wei.com,
        Keita Suzuki <keitasuzuki.park@...ab.ics.keio.ac.jp>,
        stable@...r.kernel.org, Wenwen Wang <wenwen@...uga.edu>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Cai Huoqing <cai.huoqing@...ux.dev>,
        Sean Young <sean@...s.org>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] media: dvb-core: Fix double free in dvb_register_device()

In function dvb_register_device() -> dvb_register_media_device() ->
dvb_create_media_entity(), dvb->entity is allocated and initialized. If
the initialization fails, it frees the dvb->entity, and return an error
code. The caller takes the error code and handles the error by calling
dvb_media_device_free(), which unregisters the entity and frees the
field again if it is not NULL. As dvb->entity may not NULLed in
dvb_create_media_entity() when the allocation of dvbdev->pad fails, a
double free may occur. This may also cause an Use After free in
media_device_unregister_entity().

Fix this by storing NULL to dvb->entity when it is freed.

Fixes: fcd5ce4b3936 ("media: dvb-core: fix a memory leak bug")
Cc: stable@...r.kernel.org
Cc: Wenwen Wang <wenwen@...uga.edu>

Signed-off-by: Keita Suzuki <keitasuzuki.park@...ab.ics.keio.ac.jp>
---
 drivers/media/dvb-core/dvbdev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
index 675d877a67b2..4597af108f4d 100644
--- a/drivers/media/dvb-core/dvbdev.c
+++ b/drivers/media/dvb-core/dvbdev.c
@@ -332,6 +332,7 @@ static int dvb_create_media_entity(struct dvb_device *dvbdev,
 				       GFP_KERNEL);
 		if (!dvbdev->pads) {
 			kfree(dvbdev->entity);
+			dvbdev->entity = NULL;
 			return -ENOMEM;
 		}
 	}
-- 
2.25.1