Interest rates are subject to unknown variations/ups downs and linking the amount of rent with interest rate will create uncertainty (Gharar) impermissible in Shariah. How would the Ijarah contract remain valid under this scenario?

It is one of the basic requirements of Shariah that the parties to the contract/agreemnet must exactly know its considerations. Under Ijarah agreement, amount of rent is one of the prime considerations of the agreement. So far as the parties are agreed with mutual consent upon a well-defined benchmark which would serve as a criterion for determining the rent, and whatever amount is determined, based on such benchmark, will be acceptable to both parties, therefore, there should not be any dispute. However, in order to save the parties from unforeseen losses due to the either way movement in the interest rate, the scholars have advised that there should be a floor and cap for the amount of rentals stipulated in the contract in case variable benchmarks is taken to determine the rental amount.