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SubjectRe: [net-next PATCH v4 1/3] sysctl: refactor integer handling proc code
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On Tuesday 16 February 2010 15:08:23 you wrote:
> Octavian Purdila wrote:
> > On Tuesday 16 February 2010 10:41:07 you wrote:
> >>> +
> >>> + if (!write && !first && left && !err)
> >>> + err = proc_put_newline(&buffer, &left);
> >>> + if (write && !err)
> >>> + err = proc_skip_wspace(&buffer, &left);
> >>> + if (err == -EFAULT /* do we really need to check for -EFAULT? */
> >>> || + (write && first))
> >>> + return err ? : -EINVAL;
> >>
> >> The logic here seems messy, adding one or two goto's may help?
> >
> > OK, I'll give it a try.
> >
> > What about the EFAULT check, is that really required?
>
> I think so, it means to keep the errno to user-space when it is EFAULT,
> right? This seems reasonable.
>

The problem I see is that this way we don't actually acknowledge some of the
set values, e.g. say that we have buffer="1 2 3" and length = 100. Although we
do accept values 1, 2 and 3 we don't acknowledge that to the user (as we would
do for, say "1 2 3 4a"), but return -EFAULT.

I think it would be better to skip this check. That means that the user will
get the ack for the 1, 2 and 3 values and next time it continues the write it
will get -EFAULT.

This will of course change the userspace ABI, albeit in a minor way, and it is
not clear to me if doing this is allowed (even if this new approach would be
the correct one).



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