Re: copy_from_user() fix

H. Peter Anvin (hpa@transmeta.com)
23 Aug 1998 12:44:34 GMT

Followup to: <k2u334hv5g.fsf@zero.aec.at>
By author: Andi Kleen <ak@muc.de>
In newsgroup: linux.dev.kernel
>
> > Linus,
>
> > I've reimplemented the fix according to Richard's suggestions.
>
> Wouldn't it be better to do the zeroing out of line? EFAULT isn't a
> path worth optimizing for, and doing it with inline code in .fixup for
> every copy bloats the kernel a lot. I think it would be better to just put a
> call to a common zero function into .fixup.
>
> As some data: my current kernel contains about 215 __copy_*_user() calls,
> if you only add 30 bytes per call then that is about 6KB alone.
>
> -Andi
>

Also, I still maintain there should be a mode to raise SIGSEGV
whenever a system call returns EFAULT. Not doing so breaks the system
call/library routine transparency, and lets bugs go uncaught.

-hpa

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