On Wed, Dec 16, 2020 at 7:15 PM KP Singh <kpsingh@xxxxxxxxxx> wrote:
>
> On Wed, Dec 16, 2020 at 1:06 AM Song Liu <songliubraving@xxxxxx> wrote:
> >
> > task_file and task_vma iter programs have access to file->f_path. Enable
> > bpf_d_path to print paths of these file.
> >
> > bpf_iter programs are generally called in sleepable context. However, it
> > is still necessary to diffientiate sleepable and non-sleepable bpf_iter
> > programs: sleepable programs have access to bpf_d_path; non-sleepable
> > programs have access to bpf_spin_lock.
> >
> > Signed-off-by: Song Liu <songliubraving@xxxxxx>
> > ---
> > kernel/trace/bpf_trace.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index 4be771df5549a..9e5f9b968355f 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -1191,6 +1191,11 @@ BTF_SET_END(btf_allowlist_d_path)
> >
> > static bool bpf_d_path_allowed(const struct bpf_prog *prog)
> > {
> > + if (prog->type == BPF_PROG_TYPE_TRACING &&
> > + prog->expected_attach_type == BPF_TRACE_ITER &&
> > + prog->aux->sleepable)
> > + return true;
>
Another try to send it on the list.
> For the sleepable/non-sleepable we have been (until now) checking
> this in bpf_tracing_func_proto (or bpf_lsm_func_proto)
>
> eg.
>
> case BPF_FUNC_copy_from_user:
> return prog->aux->sleepable ? &bpf_copy_from_user_proto : NULL;
>
> But even beyond that, I don't think this is needed.
>
> We have originally exposed the helper to both sleepable and
> non-sleepable LSM and tracing programs with an allow list.
>
> For LSM the allow list is bpf_lsm_is_sleepable_hook) but
> that's just an initial allow list and thus causes some confusion
> w.r.t to sleep ability (maybe we should add a comment there).
>
> Based on the current logic, my understanding is that
> it's okay to use the helper in the allowed hooks in both
> "lsm.s/" and "lsm/" (and the same for
> BPF_PROG_TYPE_TRACING).
>
> We would have required sleepable only if this helper called "dput"
> (which can sleep).
>
> > +
> > if (prog->type == BPF_PROG_TYPE_LSM)
> > return bpf_lsm_is_sleepable_hook(prog->aux->attach_btf_id);
> >
> > --
> > 2.24.1
> >
