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    SubjectRe: AUDIT: copy_from_user is a deathtrap.
    Alan Cox wrote:
    >
    > > In such case, linus, here is your "reasonable" example. For PPro, it
    > > is faster to copy out-of-order, and if we wanted to use that for
    > > copy_to_user, you'd have your example.
    >
    > I think there is a misunderstanding here.
    >
    > Nothing in the standards says that
    >
    > write(pipe_fd, halfmappedbuffer, 2*PAGE_SIZE)
    >
    > must return PAGE_SIZE on an error. What it seems to say is that it if an error
    > is reported then no data got written down the actual pipe itself. Putting
    > 4K into the pipe then reporting Esomething is not allowed. Copying 4K into
    > a buffer faulting and erroring with Efoo then throwing away the buffer is
    > allowed

    write might be the easy case. But what about read?
    Is a failing read allowed to change the userspace
    memory?

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