During v4.3 when the overflow/underflow check was relaxed by
commit c72c5250:

  commit c72c5250
  Author: Roland Dreier <roland@purestorage.com>
  Date:   Wed Jul 22 15:08:18 2015 -0700

       target: allow underflow/overflow for PR OUT etc. commands

to allow underflow/overflow for Windows compliance + FCP, a
consequence was to allow control CDBs to process overflow
data for iscsi-target with immediate data as well.

As per Roland's original change, continue to allow underflow
cases for control CDBs to make Windows compliance + FCP happy,
but until overflow for control CDBs is supported tree-wide,
explicitly reject all control WRITEs with overflow following
pre v4.3.y logic.
Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Roland Dreier <roland@purestorage.com>
Cc: <stable@vger.kernel.org> # v4.3+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>