netdev - Re: [PATCH net-next v4 08/10] net: openvswitch: fix possible memleak on destroy flow-table

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Message-ID: <CAOrHB_BADQMdhFk4a8BJ0qaUeLf+2+H=cLf9q80U2g1AxewY2A@mail.gmail.com>
Date:   Tue, 29 Oct 2019 00:37:56 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Tonghao Zhang <xiangxia.m.yue@...il.com>
Cc:     Greg Rose <gvrose8192@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        ovs dev <dev@...nvswitch.org>
Subject: Re: [PATCH net-next v4 08/10] net: openvswitch: fix possible memleak
 on destroy flow-table

On Sun, Oct 27, 2019 at 11:49 PM Tonghao Zhang <xiangxia.m.yue@...il.com> wrote:
>
> On Thu, Oct 24, 2019 at 3:14 PM Pravin Shelar <pshelar@....org> wrote:
> >
> > On Tue, Oct 22, 2019 at 7:35 PM Tonghao Zhang <xiangxia.m.yue@...il.com> wrote:
> > >
> > > On Tue, Oct 22, 2019 at 2:58 PM Pravin Shelar <pshelar@....org> wrote:
> > > >
> > ...
> >
...
> > >  struct sw_flow *ovs_flow_tbl_dump_next(struct table_instance *ti,
> > > @@ -400,10 +458,9 @@ static struct table_instance
> > > *table_instance_rehash(struct table_instance *ti,
> > >         return new_ti;
> > >  }
> > >
> > > -int ovs_flow_tbl_flush(struct flow_table *flow_table)
> > > +int ovs_flow_tbl_flush(struct flow_table *table)
> > >  {
> > > -       struct table_instance *old_ti, *new_ti;
> > > -       struct table_instance *old_ufid_ti, *new_ufid_ti;
> > > +       struct table_instance *new_ti, *new_ufid_ti;
> > >
> > >         new_ti = table_instance_alloc(TBL_MIN_BUCKETS);
> > >         if (!new_ti)
> > > @@ -412,16 +469,12 @@ int ovs_flow_tbl_flush(struct flow_table *flow_table)
> > >         if (!new_ufid_ti)
> > >                 goto err_free_ti;
> > >
> > > -       old_ti = ovsl_dereference(flow_table->ti);
> > > -       old_ufid_ti = ovsl_dereference(flow_table->ufid_ti);
> > > +       table_instance_destroy(table, true);
> > >
> > This would destroy running table causing unnecessary flow miss. Lets
> > keep current scheme of setting up new table before destroying current
> > one.
> >
> > > -       rcu_assign_pointer(flow_table->ti, new_ti);
....
...
>  /* Must be called with OVS mutex held. */
>  void ovs_flow_tbl_remove(struct flow_table *table, struct sw_flow *flow)
>  {
> @@ -752,17 +794,7 @@ void ovs_flow_tbl_remove(struct flow_table
> *table, struct sw_flow *flow)
>         struct table_instance *ufid_ti = ovsl_dereference(table->ufid_ti);
>
>         BUG_ON(table->count == 0);
> -       hlist_del_rcu(&flow->flow_table.node[ti->node_ver]);
> -       table->count--;
> -       if (ovs_identifier_is_ufid(&flow->id)) {
> -               hlist_del_rcu(&flow->ufid_table.node[ufid_ti->node_ver]);
> -               table->ufid_count--;
> -       }
> -
> -       /* RCU delete the mask. 'flow->mask' is not NULLed, as it should be
> -        * accessible as long as the RCU read lock is held.
> -        */
> -       flow_mask_remove(table, flow->mask);
> +       table_instance_remove(table, ti, ufid_ti, flow, true);
>  }
Lets rename table_instance_remove() to imply it is freeing a flow.
Otherwise looks good.