Subject: Re: [PATCH net-next 1/4] bpf: Fix and simplifications on inline map lookup

From: Daniel Borkmann <[email-masked]>
Date: Wed, 22 Mar 2017 20:33:16 +0100

On 03/22/2017 06:00 PM, Martin KaFai Lau wrote:
> Fix in verifier:
> For the same bpf_map_lookup_elem() instruction (i.e. "call 1"),
> a broken case is "a different type of map could be used for the
> same lookup instruction". For example, an array in one case and a
> hashmap in another.  We have to resort to the old dynamic call behavior
> in this case.  The fix is to check for collision on insn_aux->map_ptr.
> If there is collision, don't inline the map lookup.
>
> Please see the "do_reg_lookup()" in test_map_in_map_kern.c in the later
> patch for how-to trigger the above case.
>
> Simplifications on array_map_gen_lookup():
> 1. Calculate elem_size from map->value_size.  It removes the
>     need for 'struct bpf_array' which makes the later map-in-map
>     implementation easier.
> 2. Remove the 'elem_size == 1' test
>
> Fixes: 81ed18ab3098 ("bpf: add helper inlining infra and optimize map_array lookup")
> Signed-off-by: Martin KaFai Lau <[email-masked]>
> Acked-by: Alexei Starovoitov <[email-masked]>

Ok, makes sense (could have been split into two actually).

Acked-by: Daniel Borkmann <[email-masked]>