Re: [PATCH v10 04/25] tools/libxenevtchn: add possibility to not close file descriptor on exec

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/12/2020 06:06, Jürgen Groß wrote:
> On 15.12.20 19:09, Andrew Cooper wrote: 
>>
>> Additionally, something in core.c should check for unknown flags and
>> reject them them with EINVAL.  It was buggy that this wasn't done
>> before, and really needs to be implemented before we start having cases
>> where people might plausibly pass something other than 0.
>
> Are you sure this is safe? I'm not arguing against it, but we considered
> to do that and didn't dare to.

Well - you're already breaking things by adding meaning to bit 0 where
it was previously ignored.

But fundamentally - any caller passing non-zero to begin with is buggy,
and it will be less bad to fix up our input validation and given them a
clean EINVAL now.

The alternative is no error and some weird side effect when we implement
whichever bit they were settings.

~Andrew