netdev - Re: size overflow in function qdisc_tree_decrease_qlen net/sched/sch

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Date:	Tue, 01 Dec 2015 11:09:24 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Cong Wang <cwang@...pensource.com>
Cc:	pageexec@...email.hu, Daniele Fucini <dfucini@...il.com>,
	netdev <netdev@...r.kernel.org>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	David Miller <davem@...emloft.net>, spender@...ecurity.net,
	re.emese@...il.com
Subject: Re: size overflow in function qdisc_tree_decrease_qlen
 net/sched/sch_api.c

On Tue, 2015-12-01 at 10:43 -0800, Cong Wang wrote:

> This smells hacky... Another way to fix this is to hold the qdisc tree
> lock in mq_dump(), since it is not a hot path (comparing with
> enqueue/dequeue)?

Really ? Which qdisc tree lock will protect you exactly ???

Whole point of MQ is that each TX queue has its own lock.

So multiple cpus can call qdisc_tree_decrease_qlen() at the same time,
holding their own lock.

Clearly modifying mq 'data' is wrong.


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