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    SubjectRe: Bogus buffer length check in linux-2.6.11 read()
    linux-os wrote:
    >
    > The attached file shows that the kernel thinks it's doing
    > something helpful by checking the length of the input
    > buffer for a read(). It will return "Bad Address" until
    > the length is 1632 bytes. Apparently the kernel thinks
    > 1632 is a good length!

    Likely because only 1632 bytes of memory is accessible after the start
    of the buf buffer, and trying to read in more than that results in
    copy_to_user failing to write some data.

    >
    > Did anybody consider the overhead necessary to do this
    > and the fact that the kernel has no way of knowing if
    > the pointer to the buffer is valid until it actually
    > does the write. What was wrong with copy_to_user()?
    > Why is there the additional bogus check?

    What additional check?

    --
    Robert Hancock Saskatoon, SK, Canada
    To email, remove "nospam" from hancockr@nospamshaw.ca
    Home Page: http://www.roberthancock.com/

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