Messages in this thread | | | Subject | Re: KASAN: use-after-free Read in pfifo_fast_enqueue | From | Eric Dumazet <> | Date | Wed, 14 Mar 2018 17:47:11 -0700 |
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On 03/14/2018 05:16 PM, Eric Dumazet wrote:
> > typical use after free... > > diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c > index 190570f21b208d5a17943360a3a6f85e1c2a2187..663e016491773f40f81d9bbfeab3dd68e1c2fc5c 100644 > --- a/net/sched/sch_generic.c > +++ b/net/sched/sch_generic.c > @@ -628,6 +628,7 @@ static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc, > int band = prio2band[skb->priority & TC_PRIO_MAX]; > struct pfifo_fast_priv *priv = qdisc_priv(qdisc); > struct skb_array *q = band2list(priv, band); > + unsigned int pkt_len = qdisc_pkt_len(skb); > int err; > > err = skb_array_produce(q, skb); > @@ -636,7 +637,7 @@ static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc, > return qdisc_drop_cpu(skb, qdisc, to_free); > > qdisc_qstats_cpu_qlen_inc(qdisc); > - qdisc_qstats_cpu_backlog_inc(qdisc, skb); > + this_cpu_add(qdisc->cpu_qstats->backlog, pkt_len); > return NET_XMIT_SUCCESS; > } > There is also a similar issue right after qdisc_enqueue_skb_bad_txq() call.
We should move the following code in qdisc_enqueue_skb_bad_txq() to benefit from the locking
if (qdisc_is_percpu_stats(q)) { qdisc_qstats_cpu_backlog_inc(q, nskb); qdisc_qstats_cpu_qlen_inc(q); } else { qdisc_qstats_backlog_inc(q, nskb); q->q.qlen++; }
I will post a patch with the two fixes.
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