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SubjectRe: [PATCH rdma-rc v2] RDMA/core: Simplify addition of restrack object
On Thu, Jun 24, 2021 at 02:48:41PM -0300, Jason Gunthorpe wrote:
> On Tue, Jun 08, 2021 at 08:23:48AM +0300, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@nvidia.com>
> >
> > Change location of rdma_restrack_add() callers to be near attachment
> > to device logic. Such improvement fixes the bug where task_struct was
> > acquired but not released, causing to resource leak.
> >
> > ucma_create_id() {
> > ucma_alloc_ctx();
> > rdma_create_user_id() {
> > rdma_restrack_new();
> > rdma_restrack_set_name() {
> > rdma_restrack_attach_task.part.0(); <--- task_struct was gotten
> > }
> > }
> > ucma_destroy_private_ctx() {
> > ucma_put_ctx();
> > rdma_destroy_id() {
> > _destroy_id() <--- id_priv was freed
> > }
> > }
> > }
>
> I still don't understand this patch
>
> > @@ -1852,6 +1849,7 @@ static void _destroy_id(struct rdma_id_private *id_priv,
> > {
> > cma_cancel_operation(id_priv, state);
> >
> > + rdma_restrack_del(&id_priv->res);
> > if (id_priv->cma_dev) {
> > if (rdma_cap_ib_cm(id_priv->id.device, 1)) {
> > if (id_priv->cm_id.ib)
> > @@ -1861,7 +1859,6 @@ static void _destroy_id(struct rdma_id_private *id_priv,
> > iw_destroy_cm_id(id_priv->cm_id.iw);
> > }
> > cma_leave_mc_groups(id_priv);
> > - rdma_restrack_del(&id_priv->res);
> > cma_release_dev(id_priv);
>
> This seems to be the only hunk that is actually necessary, ensuring a
> non-added ID is always cleaned up is the necessary step to fixing the
> trace above.
>
> What is the rest of this doing?? It looks wrong:
>
> int rdma_bind_addr(struct rdma_cm_id *id, struct sockaddr *addr)
> {
> [..]
> ret = cma_get_port(id_priv);
> if (ret)
> goto err2;
> err2:
> [..]
> if (!cma_any_addr(addr))
> rdma_restrack_del(&id_priv->res);
>
> Which means if rdma_bind_addr() fails then restrack will discard the
> task, even though the cm_id is still valid! The ucma is free to try
> bind again and keep using the ID.

"Failure to bind" means that cma_attach_to_dev() needs to be unwind.

It is the same if rdma_restrack_add() inside that function like in this
patch or in the line before rdma_bind_addr() returns as it was in
previous code.

Thanks

>
> Jason

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