netdev - Re: [PATCH net-next 2/4] bpf/verifier: remove varlen_map_value

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Message-ID: <32c86ed1-c94e-ce9b-0639-17f597cd3d61@fb.com>
Date:   Tue, 22 Aug 2017 08:17:27 -0700
From:   Alexei Starovoitov <ast@...com>
To:     Edward Cree <ecree@...arflare.com>, <davem@...emloft.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>
CC:     <netdev@...r.kernel.org>,
        iovisor-dev <iovisor-dev@...ts.iovisor.org>
Subject: Re: [PATCH net-next 2/4] bpf/verifier: remove varlen_map_value_access
 flag

On 8/22/17 6:26 AM, 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: Alexei Starovoitov <ast@...nel.org>