On Sat, Jun 4, 2022 at 1:27 AM Martin KaFai Lau <kafai@xxxxxx> wrote:
>
> On Fri, Jun 03, 2022 at 11:11:58PM -0700, Martin KaFai Lau wrote:
> > > @@ -549,9 +655,15 @@ static int __cgroup_bpf_attach(struct cgroup *cgrp,
> > > bpf_cgroup_storages_assign(pl->storage, storage);
> > > cgrp->bpf.flags[atype] = saved_flags;
> > >
> > > + if (type == BPF_LSM_CGROUP && !old_prog) {
> > hmm... I think this "!old_prog" test should not be here.
> >
> > In allow_multi, old_prog can be NULL but it still needs
> > to bump the shim_link's refcnt by calling
> > bpf_trampoline_link_cgroup_shim().
> >
> > This is a bit tricky. Does it make sense ?
> I think I read the "!"old_prog upside-down. I think I got the
> intention here now after reading some latter patches.
> It is to save a bpf_trampoline_link_cgroup_shim() and unlink
> for the replace case ? I would prefer not to do this.
> It is quite confusing to read and does not save much.
Ok, let me try to drop it!
> > > + err = bpf_trampoline_link_cgroup_shim(new_prog, &tgt_info, atype);
> > > + if (err)
> > > + goto cleanup;
> > > + }
> > > +
> > > err = update_effective_progs(cgrp, atype);
> > > if (err)
> > > - goto cleanup;
> > > + goto cleanup_trampoline;
> > >
> > > if (old_prog)
> > Then it needs a bpf_trampoline_unlink_cgroup_shim(old_prog) here.
> >
> > > bpf_prog_put(old_prog);
> > > @@ -560,6 +672,10 @@ static int __cgroup_bpf_attach(struct cgroup *cgrp,
> > > bpf_cgroup_storages_link(new_storage, cgrp, type);
> > > return 0;
> > >
> > > +cleanup_trampoline:
> > > + if (type == BPF_LSM_CGROUP && !old_prog)
> > The "!old_prog" test should also be removed.
> >
> > > + bpf_trampoline_unlink_cgroup_shim(new_prog);
> > > +
> > > cleanup:
> > > if (old_prog) {
> > > pl->prog = old_prog;
