netdev - Re: [Patch net-next v2] net_sched: use idr to allocate bpf filter handles

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Date:   Tue, 26 Sep 2017 01:47:57 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Cong Wang <xiyou.wangcong@...il.com>
CC:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Chris Mi <chrism@...lanox.com>,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [Patch net-next v2] net_sched: use idr to allocate bpf filter
 handles

On 09/26/2017 01:11 AM, Cong Wang wrote:
> On Mon, Sep 25, 2017 at 2:16 PM, Daniel Borkmann <daniel@...earbox.net> wrote:
>> On 09/25/2017 07:13 PM, Cong Wang wrote:
[...]
>> There's this condition in the code before above idr allocations,
>> I think also in other classifiers:
>>
>>          if (oldprog) {
>>                  if (handle && oldprog->handle != handle) {
>>                          ret = -EINVAL;
>>                          goto errout;
>>                  }
>>          }
>
> Sure. If we use handle to find oldprog, it should have the
> same handle. cls_bpf_get() guarantees it. This check is
> redundant.

Good point, we should just test for 'oldprog && oldprog->handle !=
handle' and bail out then, otherwise it's just irritating. I can
see to fix this up later. Seems fine to me then, thanks!