bpf: Align CAP_NET_ADMIN checks with bpf_capable() approach

bpf: Align CAP_NET_ADMIN checks with bpf_capable() approach

Within BPF syscall handling code CAP_NET_ADMIN checks stand out a bit
compared to CAP_BPF and CAP_PERFMON checks. For the latter, CAP_BPF or
CAP_PERFMON are checked first, but if they are not set, CAP_SYS_ADMIN
takes over and grants whatever part of BPF syscall is required.

Similar kind of checks that involve CAP_NET_ADMIN are not so consistent.
One out of four uses does follow CAP_BPF/CAP_PERFMON model: during
BPF_PROG_LOAD, if the type of BPF program is "network-related" either
CAP_NET_ADMIN or CAP_SYS_ADMIN is required to proceed.

But in three other cases CAP_NET_ADMIN is required even if CAP_SYS_ADMIN
is set:
  - when creating DEVMAP/XDKMAP/CPU_MAP maps;
  - when attaching CGROUP_SKB programs;
  - when handling BPF_PROG_QUERY command.

This patch is changing the latter three cases to follow BPF_PROG_LOAD
model, that is allowing to proceed under either CAP_NET_ADMIN or
CAP_SYS_ADMIN.

This also makes it cleaner in subsequent BPF token patches to switch
wholesomely to a generic bpf_token_capable(int cap) check, that always
falls back to CAP_SYS_ADMIN if requested capability is missing.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-2-andrii@kernel.org