Oversecured lender not entitled to attorney fees for litigation with guarantor or for unsuccessful litigation with debtor with respect to whether fees for litigating with guarantor were recoverable from debtor. To be recoverable under § 506(b), fees must have been provided for by the agreement. Provision for fees “enforcing this note” did not include enforcing separate contract with guarantor and did not reach fees for unsuccessfully litigating with debtor whether debtor was responsible for the fees incurred litigating with the guarantor.