linux-kernel - [PATCH 4.9 218/223] media: cpia2_usb: first wake up, then free in disconnect

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Date:   Fri,  2 Aug 2019 11:37:23 +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, Oliver Neukum <oneukum@...e.com>,
        syzbot+0c90fc937c84f97d0aa6@...kaller.appspotmail.com,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Subject: [PATCH 4.9 218/223] media: cpia2_usb: first wake up, then free in disconnect

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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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
@@ -909,7 +909,6 @@ 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");
@@ -921,6 +920,8 @@ 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");
 }