bpf: disallow bpf tc programs access current->pid,uid

Accessing current->pid/uid from cls_bpf may lead to misleading results and
should not be used when TC classifiers need accurate information about pid/uid.

Signed-off-by: Alexei Starovoitov <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/filter.c

···
 		return &bpf_l4_csum_replace_proto;
 	case BPF_FUNC_clone_redirect:
 		return &bpf_clone_redirect_proto;
-	case BPF_FUNC_get_current_pid_tgid:
-		return &bpf_get_current_pid_tgid_proto;
-	case BPF_FUNC_get_current_uid_gid:
-		return &bpf_get_current_uid_gid_proto;
-	case BPF_FUNC_get_current_comm:
-		return &bpf_get_current_comm_proto;
 	default:
 		return sk_filter_func_proto(func_id);
 	}