Re: [PATCH bpf-next] bpf: Enforce 'return 0' in BTF-enabled raw_tp programs

Andrii Nakryiko
2019-10-29T04:32:45Z

On 10/28/19 8:24 PM, Alexei Starovoitov wrote:
> The return value of raw_tp programs is ignored by __bpf_trace_run()
> that calls them. The verifier also allows any value to be returned.
> For BTF-enabled raw_tp lets enforce 'return 0', so that return value
> can be used for something in the future.
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---

Looks good, if the return value is ignored, no need to specify anything
but 0 for now.

Acked-by: Andrii Nakryiko <andriin@fb.com>

> kernel/bpf/verifier.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index c59778c0fc4d..6b0de04f8b91 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -6279,6 +6279,11 @@ static int check_return_code(struct bpf_verifier_env *env)
> case BPF_PROG_TYPE_CGROUP_SYSCTL:
> case BPF_PROG_TYPE_CGROUP_SOCKOPT:
> break;
> + case BPF_PROG_TYPE_RAW_TRACEPOINT:
> + if (!env->prog->aux->attach_btf_id)
> + return 0;
> + range = tnum_const(0);
> + break;
> default:
> return 0;
> }
>