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

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Jan 09, 2023 at 08:19:31AM -0800, Song Liu wrote:
> On Mon, Jan 9, 2023 at 6:37 AM Jiri Olsa <jolsa@kernel.org> 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@kernel.org>
> > ---
> >  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?

ok

> 
> > +{
> > +       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?

ok, will add

thanks,
jirka