target: Re-add check to reject control WRITEs with overflow data

During v4.3 when the overflow/underflow check was relaxed by
commit c72c525022:

  commit c72c5250224d475614a00c1d7e54a67f77cd3410
  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>

1 files changed, 18 insertions, 5 deletions

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 37f57357d4a0..6025935036c9 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1160,15 +1160,28 @@ target_cmd_size_check(struct se_cmd *cmd, unsigned int size)
         if (cmd->unknown_data_length) {
                 cmd->data_length = size;
         } else if (size != cmd->data_length) {
-                pr_warn("TARGET_CORE[%s]: Expected Transfer Length:"
+                pr_warn_ratelimited("TARGET_CORE[%s]: Expected Transfer Length:"
                         " %u does not match SCSI CDB Length: %u for SAM Opcode:"
                         " 0x%02x\n", cmd->se_tfo->get_fabric_name(),
                                 cmd->data_length, size, cmd->t_task_cdb[0]);
 
-                if (cmd->data_direction == DMA_TO_DEVICE &&
-                    cmd->se_cmd_flags & SCF_SCSI_DATA_CDB) {
-                        pr_err("Rejecting underflow/overflow WRITE data\n");
-                        return TCM_INVALID_CDB_FIELD;
+                if (cmd->data_direction == DMA_TO_DEVICE) {
+                        if (cmd->se_cmd_flags & SCF_SCSI_DATA_CDB) {
+                                pr_err_ratelimited("Rejecting underflow/overflow"
+                                                   " for WRITE data CDB\n");
+                                return TCM_INVALID_CDB_FIELD;
+                        }
+                        /*
+                         * Some fabric drivers like iscsi-target still expect to
+                         * always reject overflow writes.  Reject this case until
+                         * full fabric driver level support for overflow writes
+                         * is introduced tree-wide.
+                         */
+                        if (size > cmd->data_length) {
+                                pr_err_ratelimited("Rejecting overflow for"
+                                                   " WRITE control CDB\n");
+                                return TCM_INVALID_CDB_FIELD;
+                        }
                 }
                 /*
                  * Reject READ_* or WRITE_* with overflow/underflow for