iser-target: Fix wrong allocation in the case of an empty text message

if text message dlength is 0, don't allocate a buffer for it, pass
NULL to iscsit_process_text_cmd.
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/infiniband/ulp/isert/ib_isert.c

@@ -1351,18 +1351,20 @@ isert_handle_text_cmd(struct isert_conn *isert_conn, struct isert_cmd *isert_cmd
 	struct iscsi_conn *conn = isert_conn->conn;
 	u32 payload_length = ntoh24(hdr->dlength);
 	int rc;
-	unsigned char *text_in;
+	unsigned char *text_in = NULL;
 
 	rc = iscsit_setup_text_cmd(conn, cmd, hdr);
 	if (rc < 0)
 		return rc;
 
+	if (payload_length) {
 		text_in = kzalloc(payload_length, GFP_KERNEL);
 		if (!text_in) {
 			isert_err("Unable to allocate text_in of payload_length: %u\n",
 				  payload_length);
 			return -ENOMEM;
 		}
+	}
 	cmd->text_in_ptr = text_in;
 
 	memcpy(cmd->text_in_ptr, &rx_desc->data[0], payload_length);