A number of Championship clubs, including Blackpool and Peterborough United, have made moves for Hall in the last few weeks.
However, none were able to agree terms for the player and now Warnock has made his move.
After talks between the two clubs, Sky Sports understands Leeds have now agreed a fee for Hall - which they will pay in January when the transfer window opens.
Hall, 24, who will hold talks with Leeds over the weekend ahead of completing the move, will sign a loan deal which will become permanent next year.
