vfio-ccw: fence off transport mode

[ Upstream commit 9851bc77 ]

vfio-ccw only supports command mode for channel programs, not transport
mode. User space is supposed to already take care of that and pass us
command-mode ORBs only, but better make sure and return an error to
the caller instead of trying to process tcws as ccws.
Reviewed-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Acked-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/s390/cio/vfio_ccw_fsm.c

@@ -129,6 +129,11 @@ static void fsm_io_request(struct vfio_ccw_private *private,
 	if (scsw->cmd.fctl & SCSW_FCTL_START_FUNC) {
 		orb = (union orb *)io_region->orb_area;
 
+		/* Don't try to build a cp if transport mode is specified. */
+		if (orb->tm.b) {
+			io_region->ret_code = -EOPNOTSUPP;
+			goto err_out;
+		}
 		io_region->ret_code = cp_init(&private->cp, mdev_dev(mdev),
 					      orb);
 		if (io_region->ret_code)