Re: [RFC] copy_from_user races with readpage

[Andrew Morton]

Andrew Morton <akpm@xxxxxxxx> wrote:
>
> The application is being a bit silly, because the read will return
> indeterminate results depending on whether it gets there before or after
> the write.  But that's assuming that the read is reading the part of the
> page which the writer is writing.  If the reader is reading bytes 1000-1010
> and the writer is writing bytes 990-1000 then the reader is being non-silly
> and would be justifiably surprised to see zeroes.
> 

No, that's wrong, isn't it?  If the reader is reading parts of the page
which the writer isn't writing then __copy_from_user_inatomic() won't touch
that part of the page.

So it's only the SillyApp which we're dealing with here.

So hrm.  Yes, I guess we should still fix it.
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