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From: Cong Wang <xiyou.wangcong@gmail.com>
To: Linux Kernel Network Developers <netdev@vger.kernel.org>
Cc: Lucas Bates <lucasb@mojatatu.com>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	Jamal Hadi Salim <jhs@mojatatu.com>,
	Jiri Pirko <jiri@resnulli.us>
Subject: Re: [Patch net 2/2] net_sched: hold netns refcnt for each action
Date: Fri, 3 Nov 2017 18:15:27 -0700	[thread overview]
Message-ID: <CAM_iQpV=2dKPqGmCUD5W3Ekd600E0+h39e_y2PTgwKW1xG-+WQ@mail.gmail.com> (raw)
In-Reply-To: <20171101172350.12842-3-xiyou.wangcong@gmail.com>

On Wed, Nov 1, 2017 at 10:23 AM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> TC actions have been destroyed asynchronously for a long time,
> previously in a RCU callback and now in a workqueue. If we
> don't hold a refcnt for its netns, we could use the per netns
> data structure, struct tcf_idrinfo, after it has been freed by
> netns workqueue.
>
> Hold refcnt to ensure netns destroy happens after all actions
> are gone.

This in fact is wrong. If we hold that refcnt, the netns can never
be destroyed until all actions are destroyed by user, this breaks
our netns design.

I am going to send a revert and a right way to fix it. It is more
complicated that I thought due to all of these flying RCU callbacks
and workqueue again, sigh...

Sorry about it.

  reply	other threads:[~2017-11-04  1:15 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-01 17:23 [Patch net 0/2] net_sched: fix a use-after-free for tc actions Cong Wang
2017-11-01 17:23 ` [Patch net 1/2] net_sched: acquire RTNL in tc_action_net_exit() Cong Wang
2017-11-01 17:23 ` [Patch net 2/2] net_sched: hold netns refcnt for each action Cong Wang
2017-11-04  1:15   ` Cong Wang [this message]
2017-11-03  1:30 ` [Patch net 0/2] net_sched: fix a use-after-free for tc actions David Miller

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