From: David Miller <davem@davemloft.net>
To: xiyou.wangcong@gmail.com
Cc: netdev@vger.kernel.org, daniel@iogearbox.net, jiri@resnulli.us,
john.fastabend@gmail.com, jhs@mojatatu.com,
paulmck@linux.vnet.ibm.com, edumazet@google.com
Subject: Re: [Patch net] net_sched: remove tcf_block_put_deferred()
Date: Tue, 31 Oct 2017 11:06:55 +0900 (KST) [thread overview]
Message-ID: <20171031.110655.1489377013029699670.davem@davemloft.net> (raw)
In-Reply-To: <20171030181009.18340-1-xiyou.wangcong@gmail.com>
From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Mon, 30 Oct 2017 11:10:09 -0700
> In commit 7aa0045dadb6 ("net_sched: introduce a workqueue for RCU callbacks of tc filter")
> I defer tcf_chain_flush() to a workqueue, this causes a use-after-free
> because qdisc is already destroyed after we queue this work.
>
> The tcf_block_put_deferred() is no longer necessary after we get RTNL
> for each tc filter destroy work, no others could jump in at this point.
> Same for tcf_chain_hold(), we are fully serialized now.
>
> This also reduces one indirection therefore makes the code more
> readable. Note this brings back a rcu_barrier(), however comparing
> to the code prior to commit 7aa0045dadb6 we still reduced one
> rcu_barrier(). For net-next, we can consider to refcnt tcf block to
> avoid it.
>
> Fixes: 7aa0045dadb6 ("net_sched: introduce a workqueue for RCU callbacks of tc filter")
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Jiri Pirko <jiri@resnulli.us>
> Cc: John Fastabend <john.fastabend@gmail.com>
> Cc: Jamal Hadi Salim <jhs@mojatatu.com>
> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Applied, thanks for fixing this use-after-free so quickly.
This will be another fun merge into net-next :-)
next prev parent reply other threads:[~2017-10-31 2:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-30 18:10 [Patch net] net_sched: remove tcf_block_put_deferred() Cong Wang
2017-10-31 2:06 ` David Miller [this message]
2017-10-31 10:40 ` Jiri Pirko
2017-10-31 21:47 ` Cong Wang
2017-11-01 8:11 ` Jiri Pirko
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