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.
>
> > + 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;
