Re: [PATCH v13 net-next 07/11] bpf: verifier (add ability to receive verification log)

[Daniel Borkmann]

On 09/18/2014 04:34 PM, Alexei Starovoitov wrote:
> On Wed, Sep 17, 2014 at 11:44 PM, Daniel Borkmann <dborkman@xxxxxxxxxx> wrote:
...
> > Sure, you will never get a full compatibility on that regard
> > while backwards compatibility needs to be guaranteed on the
> > other hand. I looked at perf_copy_attr() implementation and I
> > think that we should mimic it in a very similar way as it
> > exactly solves what we need.
> >
> > For example, it will return with -EINVAL for (size > PAGE_SIZE)
> > and (size < PERF_ATTR_SIZE_VER0) where PAGE_SIZE has been chosen
> > as an arbitrary hard upper limit where it is believed that it will
> > never grow beyond that large limit in future.
> >
> > So this is a more loose constraint than what we currently do,
> > that is, -EINVAL on (size > sizeof(attr)) where attr is the
> > currently known size of a specific kernel. That would at least
> > be a start, you won't be able to cover everything though, but
> > it would allow to address the issue raised when running with
> > a basic feature set.
>
> you missed my point. We should not 'do a start', since it
> doesn't help user space in the long run and only makes
> kernel more complex.

Sorry, I don't think I missed your point. But if you see things
differently, fair enough, it was just a suggestion.
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