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    SubjectRe: [RFC] prevent "dd if=/dev/mem" crash
    Bjorn Helgaas <bjorn.helgaas@hp.com> wrote:
    >
    > Old behavior:
    >
    > # dd if=/dev/mem of=/dev/null
    > <unrecoverable machine check>

    I recently fixed this for ia32 by changing copy_to_user() to not oops if
    the source address generated a fault. Similarly copy_from_user() returns
    an error if the destination generates a fault.

    In other words: drivers/char/mem.c requires that the architecture's
    copy_*_user() functions correctly handle faults on either the source or
    dest of the copy.

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