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    Subjecterror in msync(2) or am I missing something?
    Hello guys,

    In the msync(2) (source mm/filemap.c/sys_msync()) function there is a piece of
    code:

    len = (len + ~PAGE_MASK) & PAGE_MASK;
    end = start + len;
    if (end < start)
    goto out;
    if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
    goto out;
    error = 0;
    if (end == start)
    goto out;

    Now, len is size_t (unsigned int) so it can hardly ever become negative. So,
    can't one simply rewrite the code as:

    if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
    goto out;
    error = 0;
    if (!len)
    goto out;

    or even better:

    if (!len)
    goto out;
    if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
    goto out;

    because one expects EINVAL when len == 0 anyway.

    Since Linux's code is probably right (because), I assume that I must be wrong.
    Hence the question - what am I missing there?

    Regards,
    ------ -------- --------- -------- -- - -- ---- --
    Tigran A. Aivazian | http://www.sco.com
    Escalations Research Group | tel: +44-(0)1923-813796
    Santa Cruz Operation Ltd | Email: tigran@sco.com


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