Re: [patch] net_sched: stack info leak in cbq_dump_wrr()

Joe Perches
2013-07-29T20:12:31Z

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?