On Mon, May 23, 2022 at 07:15:03PM -0700, Stanislav Fomichev wrote:

quoted

quoted

+             return;
+
+     WARN_ON_ONCE(__bpf_trampoline_unlink_prog(&shim_link->tramp_link, shim_link->tr));
+     kfree(shim_link);

How about shim_link->tramp_link.link.prog, is the prog freed ?

Considering the bpf_link_put() does bpf_prog_put(link->prog).
Is there a reason the bpf_link_put() not used and needs to
manage its own shim_link->refcnt here ?

Good catch, I've missed the bpf_prog_put(link->prog) part. Let me see
if I can use the link's refcnt, it seems like I can define my own
link->ops->dealloc to call __bpf_trampoline_unlink_prog and the rest
will be taken care of.

From looking at bpf_link_free(), link->ops->release may be a better one
because the link->ops->release() will still need to use the shim_prog
(e.g. shim_prog->aux->cgroup_atype).