Re: [PATCH bpf-next] bpf: Do not allow to load sleepable BPF_TRACE_RAW_TP program

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On Mon, Jan 9, 2023 at 6:37 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Currently we allow to load any tracing program as sleepable,
> but BPF_TRACE_RAW_TP can't sleep. Making the check explicit
> for tracing programs attach types, so sleepable BPF_TRACE_RAW_TP
> will fail to load.
>
> Updating the verifier error to mention iter programs as well.
>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
>  kernel/bpf/verifier.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index fa4c911603e9..121a64ee841a 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -16743,6 +16743,18 @@ BTF_ID(func, rcu_read_unlock_strict)
>  #endif
>  BTF_SET_END(btf_id_deny)
>
> +static int can_be_sleepable(struct bpf_prog *prog)

Shall we return bool?

> +{
> +       if (prog->type == BPF_PROG_TYPE_TRACING) {
> +               return prog->expected_attach_type == BPF_TRACE_FENTRY ||
> +                      prog->expected_attach_type == BPF_TRACE_FEXIT ||
> +                      prog->expected_attach_type == BPF_MODIFY_RETURN ||
> +                      prog->expected_attach_type == BPF_TRACE_ITER;
> +       }
> +       return prog->type == BPF_PROG_TYPE_LSM ||
> +              prog->type == BPF_PROG_TYPE_KPROBE;
> +}
> +
>  static int check_attach_btf_id(struct bpf_verifier_env *env)
>  {
>         struct bpf_prog *prog = env->prog;
> @@ -16761,9 +16773,8 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
>                 return -EINVAL;
>         }
>
> -       if (prog->aux->sleepable && prog->type != BPF_PROG_TYPE_TRACING &&
> -           prog->type != BPF_PROG_TYPE_LSM && prog->type != BPF_PROG_TYPE_KPROBE) {
> -               verbose(env, "Only fentry/fexit/fmod_ret, lsm, and kprobe/uprobe programs can be sleepable\n");
> +       if (prog->aux->sleepable && !can_be_sleepable(prog)) {
> +               verbose(env, "Only fentry/fexit/fmod_ret, lsm, iter and kprobe/uprobe programs can be sleepable\n");
>                 return -EINVAL;
>         }

Maybe add a verifier test for this?

Thanks,
Song

>
> --
> 2.39.0
>



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