On Tue, Jun 3, 2025 at 2:09 PM Song Liu <song@xxxxxxxxxx> wrote:
>
> On Tue, Jun 3, 2025 at 11:40 AM Andrii Nakryiko
> <andrii.nakryiko@xxxxxxxxx> wrote:
> [...]
> > > +__bpf_kfunc struct path *bpf_iter_path_next(struct bpf_iter_path *it)
> > > +{
> > > + struct bpf_iter_path_kern *kit = (void *)it;
> > > + struct path root = {};
> > > +
> > > + if (!path_walk_parent(&kit->path, &root))
> > > + return NULL;
> > > + return &kit->path;
> > > +}
> > > +
> > > +__bpf_kfunc void bpf_iter_path_destroy(struct bpf_iter_path *it)
> > > +{
> > > + struct bpf_iter_path_kern *kit = (void *)it;
> > > +
> > > + path_put(&kit->path);
> >
> > note, destroy() will be called even if construction of iterator fails
> > or we exhausted iterator. So you need to make sure that you have
> > bpf_iter_path state where you can detect that there is no path present
> > and skip path_put().
>
> In bpf_iter_path_next(), when path_walk_parent() returns false, we
> still hold reference to kit->path, then _destroy() will release it. So we
> should be fine, no?
you still need to handle iterators that failed to be initialized,
though? And one can argue that if path_walk_parent() returns false, we
need to put that last path before returning NULL, no?
>
> Thanks,
> Song
>
> >
> > > +}
> > > +
> > > +__bpf_kfunc_end_defs();
> > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > > index a7d6e0c5928b..45b45cdfb223 100644
> > > --- a/kernel/bpf/verifier.c
> > > +++ b/kernel/bpf/verifier.c
> > > @@ -7036,6 +7036,10 @@ BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket) {
> > > struct sock *sk;
> > > };
> > >
> > > +BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct path) {
> > > + struct dentry *dentry;
> > > +};
> > > +
> > > static bool type_is_rcu(struct bpf_verifier_env *env,
> > > struct bpf_reg_state *reg,
> > > const char *field_name, u32 btf_id)
> > > @@ -7076,6 +7080,7 @@ static bool type_is_trusted_or_null(struct bpf_verifier_env *env,
> > > const char *field_name, u32 btf_id)
> > > {
> > > BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct socket));
> > > + BTF_TYPE_EMIT(BTF_TYPE_SAFE_TRUSTED_OR_NULL(struct path));
> > >
> > > return btf_nested_type_is_trusted(&env->log, reg, field_name, btf_id,
> > > "__safe_trusted_or_null");
> > > --
> > > 2.47.1
> > >
> >
