On Wednesday April 19, [email protected] 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.
However this non-silly case will not cause a problem. If the write is
writing bytes 990-1000, then only those bytes risk being zeroed by
__copy_from_user. Bytes 1000-1010 (assuming those ranges are intended
not to overlap) will not be at risk.
>
>
> I'd have thought that a sufficient fix would be to change
> __copy_from_user_inatomic() to not do the zeroing, then review all users to
> make sure that they cannot leak uninitialised memory.
I would agree with this.
NeilBrown
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