SuSv3 says: "The msync() function shall fail if:

[EBUSY]
    Some or all of the addresses in the range starting at addr and
    continuing for len bytes are locked, and MS_INVALIDATE is
    specified.

[EINVAL]
    The value of flags is invalid.

[EINVAL]
    The value of addr is not a multiple of the page size {PAGESIZE}.

[ENOMEM]
    The addresses in the range starting at addr and continuing for len
    bytes are outside the range allowed for the address space of a process
    or specify one or more pages that are not mapped."

This fixes error code of msync() of the EINVAL case.