Section 90D. Any loan made in violation of section ninety A by any person shall be discharged upon payment or tender by the debtor or any person succeeding to his interest in such real estate of the principal sum actually borrowed with interest for the period between the borrowing of said money and the payment or tender hereunder at the rate of eighteen per cent per annum. If an action is brought upon a loan coming within the purview of section ninety A, the verdict or finding entered for the plaintiff in such action shall in no event exceed the amount that would be required to discharge by payment or tender the indebtedness at the time of such verdict or finding. Any agreement whereby the borrower waives the benefits of section ninety A or releases any rights he may have acquired by virtue thereof shall be deemed to be against public policy and void. The superior court shall have jurisdiction in equity of all actions arising under said section ninety A and if a finding is made that such loan secured by any such mortgage violates said section ninety A such borrower shall be entitled to a reasonable fee for the services of his attorney in such action.