linux-kernel - [PATCH 3.16 117/132] media: cpia2_usb: first wake up, then free in disconnect

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Message-ID: <lsq.1568989415.91336269@decadent.org.uk>
Date:   Fri, 20 Sep 2019 15:23:35 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Mauro Carvalho Chehab" <mchehab+samsung@...nel.org>,
        "Oliver Neukum" <oneukum@...e.com>,
        "Hans Verkuil" <hverkuil-cisco@...all.nl>,
        syzbot+0c90fc937c84f97d0aa6@...kaller.appspotmail.com
Subject: [PATCH 3.16 117/132] media: cpia2_usb: first wake up, then free
 in disconnect

3.16.74-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Oliver Neukum <oneukum@...e.com>

commit eff73de2b1600ad8230692f00bc0ab49b166512a upstream.

Kasan reported a use after free in cpia2_usb_disconnect()
It first freed everything and then woke up those waiting.
The reverse order is correct.

Fixes: 6c493f8b28c67 ("[media] cpia2: major overhaul to get it in a working state again")

Signed-off-by: Oliver Neukum <oneukum@...e.com>
Reported-by: syzbot+0c90fc937c84f97d0aa6@...kaller.appspotmail.com
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/media/usb/cpia2/cpia2_usb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/media/usb/cpia2/cpia2_usb.c
+++ b/drivers/media/usb/cpia2/cpia2_usb.c
@@ -884,7 +884,6 @@ static void cpia2_usb_disconnect(struct
 	cpia2_unregister_camera(cam);
 	v4l2_device_disconnect(&cam->v4l2_dev);
 	mutex_unlock(&cam->v4l2_lock);
-	v4l2_device_put(&cam->v4l2_dev);
 
 	if(cam->buffers) {
 		DBG("Wakeup waiting processes\n");
@@ -897,6 +896,8 @@ static void cpia2_usb_disconnect(struct
 	DBG("Releasing interface\n");
 	usb_driver_release_interface(&cpia2_driver, intf);
 
+	v4l2_device_put(&cam->v4l2_dev);
+
 	LOG("CPiA2 camera disconnected.\n");
 }