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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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