The uplink of full-duplex multi-cell massive MEMO systems is analyzed in this paper. Besides the interference due to multi-user transmissions as in half duplex massive MIMO system-s, interference from other base stations (BSs) and self-interference coming from the base station's downlink transmission would occur, which complicates the analysis on the uplink achievable rate. To be practical, both antenna correlation and line-of-sight (LoS) path are considered in the BS-to-BS channel model. A deterministic approximation of the uplink achievable rate is derived based on random matrix theory. It is then proved that the BS-to-BS interference and self interference would asymptotically vanish. It means the asymptotic achievable rate is exactly the double of that of half-duplex transmission. With finite number of antennas per-BS, however, the BS-to-BS interference and self interference would limit the performance of full duplex. To ensure full duplex to outperform half duplex in the uplink, the number of antennas per-BS should be larger than a threshold which is also derived explicitly. Finally the accuracy of the analytical results is validated by computer simulations.