Re: [Xen-devel] [PATCH v2 39/52] xen: check parameter validity when parsing command line

[Juergen Gross <jgross@xxxxxxxx>]

On 14/08/17 14:46, Jan Beulich wrote:
>>>> On 14.08.17 at 09:08, <jgross@xxxxxxxx> wrote:
>> --- a/xen/common/kernel.c
>> +++ b/xen/common/kernel.c
>>                      optval[-1] = '\0';
>> +                    break;
> 
> Why? Applies to further break-s you add: At least in the past we
> had command line options with two handlers, where each of them
> needed to be invoked. I don't think we should make such impossible
> even if right now there aren't any such examples. Yet if you really
> mean to, then the behavioral change needs to be called out in the
> description.

While working on this I realized that this functionality has been
working only in some cases. The custom parsing functions are being
called with a copy of the option value, which they modify in some
cases. So a second handler being called would see another value as
the first handler, as long as modifying the option value keeps to be
allowed.

I see three possibilities here:

1. don't allow multiple handlers for the same parameter
2. restore the option value before calling each handler (as the
   error message I'm adding with this patch requires access to the
   whole option value this wouldn't be too hard)
3. don't allow a handler to modify the option value (solves my error
   message problem, too)

Any preferences?


Juergen

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