loop: loop_set_status_from_info() check before assignment

In the Linux kernel, the following vulnerability has been resolved:

loop: loop_set_status_from_info() check before assignment

In loop_set_status_from_info(), lo->lo_offset and lo->lo_sizelimit should
be checked before reassignment, because if an overflow error occurs, the
original correct value will be changed to the wrong value, and it will not
be changed back.

More, the original patch did not solve the problem, the value was set and
ioctl returned an error, but the subsequent io used the value in the loop
driver, which still caused an alarm:

loop_handle_cmd
do_req_filebacked
loff_t pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
lo_rw_aio
cmd->iocb.ki_pos = pos