The port B is cannot be used all of 8 bit as input port at the same time. At least 1 bit must be set to analog input pin. If you want to use all port B as 8bit input port, the following procedures are needed.
(1) read the port data which is set to other than analog input channel
(2) then, shift analog input channel to another pin by changing CH2-CH0 in ADCSR.
(3) read the data of the pin which becomes input state through (2) process.
(4) mix the data gotten from (1) and (3), then can be used as 8 bit input port data.