netdev - Re: [PATCH net-next 01/12] bpf: verifier: set reg_type on context accesses in second pass

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Date:   Thu, 12 Oct 2017 23:46:38 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
CC:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        alexei.starovoitov@...il.com
Subject: Re: [PATCH net-next 01/12] bpf: verifier: set reg_type on context
 accesses in second pass

On 10/12/2017 11:39 PM, Jakub Kicinski wrote:
> On Thu, 12 Oct 2017 23:33:21 +0200, Daniel Borkmann wrote:
>> On 10/12/2017 10:56 PM, Jakub Kicinski wrote:
>>> On Thu, 12 Oct 2017 22:43:10 +0200, Daniel Borkmann wrote:
>> [...]
>>>> It would be nice to keep the reg_type setting in one place, meaning
>>>> the callbacks themselves, so we wouldn't need to maintain this in
>>>> multiple places.
>>>
>>> Hm.. I though this was the smallest and simplest change.  I could
>>> translate the offsets but that seems wobbly.  Or try to consolidate the
>>> call into the same if () branch?  Not sure..
>>
>> Different callbacks for post-verification would be good at min as it
>> would allow to keep all the context access info in one place for a
>> given type at least.
>
> Sorry to be clear - you're suggesting adding a new callback to struct
> bpf_verifier_ops, or swapping the struct bpf_verifier_ops for a
> special post-verification one?

Either way is fine by me.

>>> As a bonus info I discovered there is a bug in -net with how things are
>>> converted.  We allow arithmetic on context pointers but then only
>>> look at the insn.off in the converter...  I'm working on a fix.
>>
>> Ohh well, good catch, indeed! :( Can you also add coverage to the
>> bpf selftests for this?
>
> Will do!

Thanks,
Daniel