DF-1919 fix check (mrsas_ioctl.c:266-267 patched predicate + bus_size_t):
  benign                 iov_len=0x0000000000000040 -> accepted (in-bounds)
  truncated-small        iov_len=0x0000000100000008 -> REJECTED (EINVAL) -- would have overflowed
  truncated-page         iov_len=0x0000000100001000 -> REJECTED (EINVAL) -- would have overflowed
  truncated-zero-lo      iov_len=0x0000000100000000 -> REJECTED (EINVAL) -- would have overflowed
  truncated-neg          iov_len=0x00000001ffffffff -> REJECTED (EINVAL) -- would have overflowed
  truncated-large        iov_len=0x0000000200000800 -> REJECTED (EINVAL) -- would have overflowed
  5/6 vectors rejected by the fix predicate.