Re: strict copy_from_user checks issues?

[Arnd Bergmann]

On Tuesday 05 January 2010, H. Peter Anvin wrote:
> What's much worse is that it adds churn to an otherwise-tested code path.
> 
> We almost need a copy_from/to_user_audited() to override the warning.
> Not that errors can't creap back in...
> 

Maybe just splitting it up into access_ok() and __copy_from_user(),
plus a comment is enough? That way we don't need to add another interface
for the rare case.

On a related topic, one interface that may actually be worth adding is
a get_user/put_user variant that can operate on full data structures
and return -EFAULT on failure rather than the number of remaining
bytes that 99% of the code never need.

	Arnd
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