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

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Date:   Thu, 09 Nov 2017 11:26:07 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     netdev@...r.kernel.org, lucasb@...atatu.com, jhs@...atatu.com,
        jiri@...nulli.us
Subject: Re: [Patch net 00/13] net_sched: close the race between call_rcu()
 and cleanup_net()

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.

Thanks.