media: cpia2_usb: first wake up, then free in disconnect

BugLink: https://bugs.launchpad.net/bugs/1840081

commit eff73de2 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: 6c493f8b ("[media] cpia2: major overhaul to get it in a working state again")
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reported-by: syzbot+0c90fc937c84f97d0aa6@syzkaller.appspotmail.com
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/media/usb/cpia2/cpia2_usb.c

@@ -884,7 +884,6 @@ static void cpia2_usb_disconnect(struct usb_interface *intf)
 	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 usb_interface *intf)
 	DBG("Releasing interface\n");
 	usb_driver_release_interface(&cpia2_driver, intf);
 
+	v4l2_device_put(&cam->v4l2_dev);
+
 	LOG("CPiA2 camera disconnected.\n");
 }