netdev - Re: [patch] net_sched: stack info leak in cbq_dump

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Date:	Tue, 30 Jul 2013 09:55:09 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Jamal Hadi Salim <jhs@...atatu.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] net_sched: stack info leak in cbq_dump_wrr()

On Mon, Jul 29, 2013 at 01:12:31PM -0700, Joe Perches wrote:
> On Mon, 2013-07-29 at 23:01 +0300, Dan Carpenter wrote:
> > On Mon, Jul 29, 2013 at 12:44:32PM -0700, Joe Perches wrote:
> > > On Mon, 2013-07-29 at 22:36 +0300, Dan Carpenter wrote:
> > > > opt.__reserved isn't cleared so we leak a byte of stack information.
> > > []
> > > > diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
> > > []
> > > > @@ -1469,6 +1469,7 @@ static int cbq_dump_wrr(struct sk_buff *skb, struct cbq_class *cl)
> > > >  	opt.allot = cl->allot;
> > > >  	opt.priority = cl->priority + 1;
> > > >  	opt.cpriority = cl->cpriority + 1;
> > > > +	opt.__reserved = 0;
> > > >  	opt.weight = cl->weight;
> > > >  	if (nla_put(skb, TCA_CBQ_WRROPT, sizeof(opt), &opt))
> > > >  		goto nla_put_failure;
> > > 
> > > Alignment isn't guaranteed here so it'd
> > > probably be better with a memset.
> > > 
> > 
> > Hm...  Which arches would align it differently?
> 
> Hey Dan.
> 
> None so far as I know, but what difference does it make
> when it's a general correctness issue?
> 

Because I would assume if these aren't aligned the same way we have
far more serious problems than just this one case.  It would change
the user space API and break network protocols.

regards,
dan carpenter
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