On Tue, May 28, 2019 at 9:59 AM Andreas Steinmetz <ast@xxxxxxxx> wrote:
>
> [sorry for crossposting but this affects both lists]
>
> BPF_PROG_TYPE_SCHED_CLS and BPF_PROG_TYPE_XDP should be allowed
> for CAP_NET_ADMIN capability. Nearly everything one can do with
> these program types can be done some other way with CAP_NET_ADMIN
> capability (e.g. NFQUEUE), but only slower.
>
> This change is similar in behaviour to the /proc/sys/net
> CAP_NET_ADMIN exemption.
>
> Overall chances are of increased security as network related
> applications do no longer require to keep CAP_SYS_ADMIN
> admin capability for network related eBPF operations.
>
> It may well be that other program types than BPF_PROG_TYPE_XDP
> and BPF_PROG_TYPE_SCHED_CLS do need the same exemption, though
> I do not have sufficient knowledge of other program types
> to be able to decide this.
>
> Preloading BPF programs is not possible in case of application
> modified or generated BPF programs, so this is no alternative.
> The verifier does prevent the BPF program from doing harmful
> things anyway.
>
> Signed-off-by: Andreas Steinmetz <ast@xxxxxxxx>
>
> --- a/kernel/bpf/syscall.c 2019-05-28 18:00:40.472841432 +0200
> +++ b/kernel/bpf/syscall.c 2019-05-28 18:17:50.162811510 +0200
> @@ -1561,8 +1561,13 @@ static int bpf_prog_load(union bpf_attr
> return -E2BIG;
> if (type != BPF_PROG_TYPE_SOCKET_FILTER &&
> type != BPF_PROG_TYPE_CGROUP_SKB &&
You should extend this if () statement instead of adding another
if () below.
Thanks,
Song
> - !capable(CAP_SYS_ADMIN))
> - return -EPERM;
> + !capable(CAP_SYS_ADMIN)) {
> + if (type != BPF_PROG_TYPE_SCHED_CLS &&
> + type != BPF_PROG_TYPE_XDP)
> + return -EPERM;
> + if(!capable(CAP_NET_ADMIN))
> + return -EPERM;
> + }
>
> bpf_prog_load_fixup_attach_type(attr);
> if (bpf_prog_load_check_attach_type(type, attr->expected_attach_type))
>
