iscsi-target: Fix non-immediate TMR reference leak

This patch fixes a se_cmd->cmd_kref reference leak that can
occur when a non immediate TMR is proceeded our of command
sequence number order, and CMDSN_LOWER_THAN_EXP is returned
by iscsit_sequence_cmd().

To address this bug, call target_put_sess_cmd() during this
special case following what iscsit_process_scsi_cmd() does
upon CMDSN_LOWER_THAN_EXP.

Cc: Mike Christie <mchristi@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/iscsi/iscsi_target.c

@@ -2094,12 +2094,14 @@ iscsit_handle_task_mgt_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 
 	if (!(hdr->opcode & ISCSI_OP_IMMEDIATE)) {
 		int cmdsn_ret = iscsit_sequence_cmd(conn, cmd, buf, hdr->cmdsn);
-		if (cmdsn_ret == CMDSN_HIGHER_THAN_EXP)
+		if (cmdsn_ret == CMDSN_HIGHER_THAN_EXP) {
 			out_of_order_cmdsn = 1;
-		else if (cmdsn_ret == CMDSN_LOWER_THAN_EXP)
+		} else if (cmdsn_ret == CMDSN_LOWER_THAN_EXP) {
+			target_put_sess_cmd(&cmd->se_cmd);
 			return 0;
-		else if (cmdsn_ret == CMDSN_ERROR_CANNOT_RECOVER)
+		} else if (cmdsn_ret == CMDSN_ERROR_CANNOT_RECOVER) {
 			return -1;
+		}
 	}
 	iscsit_ack_from_expstatsn(conn, be32_to_cpu(hdr->exp_statsn));