netdev - Re: [PATCH v2 net-next 4/5] bpf/verifier: remove varlen_map_value

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Date:   Wed, 23 Aug 2017 16:44:37 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Edward Cree <ecree@...arflare.com>, davem@...emloft.net,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Alexei Starovoitov <ast@...com>
CC:     netdev@...r.kernel.org, iovisor-dev <iovisor-dev@...ts.iovisor.org>
Subject: Re: [PATCH v2 net-next 4/5] bpf/verifier: remove varlen_map_value_access
 flag

On 08/23/2017 04:10 PM, Edward Cree wrote:
> The optimisation it does is broken when the 'new' register value has a
>   variable offset and the 'old' was constant.  I broke it with my pointer
>   types unification (see Fixes tag below), before which the 'new' value
>   would have type PTR_TO_MAP_VALUE_ADJ and would thus not compare equal;
>   other changes in that patch mean that its original behaviour (ignore
>   min/max values) cannot be restored.
> Tests on a sample set of cilium programs show no change in count of
>   processed instructions.
>
> Fixes: f1174f77b50c ("bpf/verifier: rework value tracking")
> Signed-off-by: Edward Cree <ecree@...arflare.com>

Acked-by: Daniel Borkmann <daniel@...earbox.net>