commit 8108a77515126f6db4374e8593956e20430307c0
author John Fastabend <john.fastabend@gmail.com> Fri Oct 27 09:45:34 2017 -0700
committer David S. Miller <davem@davemloft.net> Sun Oct 29 11:18:48 2017 +0900
tree 0c6e1ae0c05ad353f1fa675edcdaad6cf9b333b3
parent dea6e19f4ef746aa18b4c33d1a7fed54356796ed

bpf: bpf_compute_data uses incorrect cb structure

SK_SKB program types use bpf_compute_data to store the end of the
packet data. However, bpf_compute_data assumes the cb is stored in the
qdisc layer format. But, for SK_SKB this is the wrong layer of the
stack for this type.

It happens to work (sort of!) because in most cases nothing happens
to be overwritten today. This is very fragile and error prone.
Fortunately, we have another hole in tcp_skb_cb we can use so lets
put the data_end value there.

Note, SK_SKB program types do not use data_meta, they are failed by
sk_skb_is_valid_access().

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>