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

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Message-ID: <1448978807.25582.19.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 01 Dec 2015 06:06:47 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Daniele Fucini <dfucini@...il.com>
Cc:	Cong Wang <cwang@...pensource.com>,
	netdev <netdev@...r.kernel.org>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	David Miller <davem@...emloft.net>, spender@...ecurity.net,
	pageexec@...email.hu, 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 12:19 +0100, Daniele Fucini wrote:
> Thanks for the reply. Here's the output of `tc qdisc show`:
> https://gist.github.com/1847102c8fe08f63e9e7
> 
> Daniele
> 
> 
> On Mon, Nov 30, 2015 at 08:50:29PM -0800, Cong Wang wrote:
> > On Mon, Nov 30, 2015 at 5:00 PM, Daniele Fucini <dfucini@...il.com> wrote:
> > > Hello,
> > >
> > > I'm using a Grsecurity patched kernel (version 4.2.6-201511282239) and
> > > I'm getting system freezes due to PaX detecting a size overflow in
> > > function qdisc_tree_decrease_qlen net/sched/sch_api.c:769 whenever I use
> > > Transmission BitTorrent client.
> > >
> > > On the Grsecurity forum I was told it's probably an unintended integer
> > > underflow that I should report upstream.
> > >
> > > Here's the relevant log:
> > > https://gist.github.com/cf54ccbb12ea65e146d4
> > >
> > 
> > Looks like we miss some sch->q.qlen accounting somewhere...
> > 
> > What is your qdisc setup? Is your fq_codel the default one or you installed it
> > or some other qdisc somewhere (`tc qdisc show` could tell)?
> > 
> > I will take a deeper look tomorrow, or maybe Jamal could find something
> > before I wake up. ;)

Hmm... I do not think we ever took care of MQ in
qdisc_tree_decrease_qlen()



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