netfilter: nf_tables_offload: incorrect flow offload action array size

netfilter: nf_tables_offload: incorrect flow offload action array size

immediate verdict expression needs to allocate one slot in the flow offload
action array, however, immediate data expression does not need to do so.

fwd and dup expression need to allocate one slot, this is missing.

Add a new offload_action interface to report if this expression needs to
allocate one slot in the flow offload action array.

Fixes: be2861dc36d7 ("netfilter: nft_{fwd,dup}_netdev: add offload support")
Reported-and-tested-by: Nick Gregory <Nick.Gregory@Sophos.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
(backported from commit b1a5983f56e371046dcf164f90bfaf704d2b89f6 net.git)
[cascardo: there is no offload_stats at struct nft_expr_ops]
CVE-2022-25636
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Andrea Righi <andrea.righi@canonical.com>