netdev - Re: [Patch net 00/13] net_sched: close the race between call_rcu() and cleanup

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Date:   Wed, 8 Nov 2017 18:32:20 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Lucas Bates <lucasb@...atatu.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>
Subject: Re: [Patch net 00/13] net_sched: close the race between call_rcu()
 and cleanup_net()

On Wed, Nov 8, 2017 at 6:26 PM, David Miller <davem@...emloft.net> wrote:
> From: Cong Wang <xiyou.wangcong@...il.com>
> Date: Mon,  6 Nov 2017 13:47:17 -0800
>
>> This patchset tries to fix the race between call_rcu() and
>> cleanup_net() again. Without holding the netns refcnt the
>> tc_action_net_exit() in netns workqueue could be called before
>> filter destroy works in tc filter workqueue. This patchset
>> moves the netns refcnt from tc actions to tcf_exts, without
>> breaking per-netns tc actions.
>>
>> Patch 1 reverts the previous fix, patch 2 introduces two new
>> API's to help to address the bug and the rest patches switch
>> to the new API's. Please see each patch for details.
>>
>> I was not able to reproduce this bug, but now after adding
>> some delay in filter destroy work I manage to trigger the
>> crash. After this patchset, the crash is not reproducible
>> any more and the debugging printk's show the order is expected
>> too.
>>
>> Fixes: ddf97ccdd7cb ("net_sched: add network namespace support for tc actions")
>> Reported-by: Lucas Bates <lucasb@...atatu.com>
>> Cc: Lucas Bates <lucasb@...atatu.com>
>> Cc: Jamal Hadi Salim <jhs@...atatu.com>
>> Cc: Jiri Pirko <jiri@...nulli.us>
>> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
>
> I have to say this was a lot of churn so late in the release
> cycle.... but I ended up pulling anyways.
>
> I cannot guarantee that I will be able to push this to Linus
> in time for 4.14-final.
>

Yeah, it is kinda too late. I'd suggest you to just push the revert
to Linus for 4.14 and defer the rest to 4.15, if it's doable...

Thanks!