Add a number of sanity checks to the data that we're handling from the
CIS. Coverity has tagged it as tainted. While this data is more
trusted than your average data, we still need to do some basic
validation on it. Check ioctl return value to ensure we switch memory
targets between common and attribute as well as the lseek.

CID: 1210464, 1006640, 1006868, 1007292, 1009091, 1009822, 1009824