This paper studies joint uplink (UL) and downlink (DL) resource allocation in an orthogonal frequency-division multiple-access (OFDMA) based cloud radio access network (CRAN), where the distributed remote radio heads (RRHs) cooperatively serve the users' UL and DL transmission over different subcarriers (SCs). We aim to maximize the system throughput through jointly optimizing UL/DL scheduling, SC assignment, RRH selection and power allocation under the maximum power and fronthaul capacity constraints. We formulate the problem as a mixed integer programming problem which is nonconvex and NP-hard. We propose an optimal algorithm based on the Lagrange duality method to solve this problem. We also propose a suboptimal algorithm to further reduce the complexity. Simulation results illustrate that the proposed algorithms can considerably improve the system throughput compared to other benchmark schemes.