netdev - Re: [PATCH] net/sched: reset block pointer in tcf_block

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Message-Id: <20170811.142100.465766359895148878.davem@davemloft.net>
Date:   Fri, 11 Aug 2017 14:21:00 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     fw@...len.de, khlebnikov@...dex-team.ru, netdev@...r.kernel.org,
        jiri@...lanox.com, jhs@...atatu.com
Subject: Re: [PATCH] net/sched: reset block pointer in tcf_block_put()

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Fri, 11 Aug 2017 14:06:31 -0700

> On Fri, Aug 11, 2017 at 1:32 PM, Florian Westphal <fw@...len.de> wrote:
>> Cong Wang <xiyou.wangcong@...il.com> wrote:
>>> On Thu, Aug 10, 2017 at 2:31 AM, Konstantin Khlebnikov
>>> <khlebnikov@...dex-team.ru> wrote:
>>> > In previous API tcf_destroy_chain() could be called several times and
>>> > some schedulers like hfsc and atm use that. In new API tcf_block_put()
>>> > frees block but leaves stale pointer, second call will free it once again.
>>>
>>> Which call path do we call tcf_block_put() for multiple times on
>>> the same block? Please be specific, it is not obvious.
>>
>> you can use tools/testing/selftests/net/rtnetlink.sh to reproduce this
>> (kernel panics on delete of root qdisc).
> 
> I am sure this is not how changelog works. We have enough space
> in changelog to describe a bug, don't have to leave details in a
> following-up email which will almost surely be lost in history.

Yeah, the more information in the commit log message the better.