netdev - Re: [PATCH net v3] cls_u32: fix use after free in u32_destroy

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Date:   Mon, 5 Feb 2018 10:40:05 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>, Li Shuang <shuali@...hat.com>,
        Ivan Vecera <ivecera@...hat.com>
Subject: Re: [PATCH net v3] cls_u32: fix use after free in u32_destroy_key()

On Mon, Feb 5, 2018 at 1:20 AM, Paolo Abeni <pabeni@...hat.com> wrote:
> @@ -625,6 +627,8 @@ static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
>                         idr_destroy(&ht->handle_idr);
>                         idr_remove_ext(&tp_c->handle_idr, ht->handle);
>                         RCU_INIT_POINTER(*hn, ht->next);
> +
> +                       /* the caller ensures ht->refcnt is 0 at this point */

This comment is not needed, because there is already a WARN_ON():

 608 static int u32_destroy_hnode(struct tcf_proto *tp, struct tc_u_hnode *ht,
 609                              struct netlink_ext_ack *extack)
 610 {
 611         struct tc_u_common *tp_c = tp->data;
 612         struct tc_u_hnode __rcu **hn;
 613         struct tc_u_hnode *phn;
 614
 615         WARN_ON(ht->refcnt);


Other than this, looks good.

Thanks.