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net: sched: sch_qfq: Fix UAF in qfq_dequeue() #59

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net: sched: sch_qfq: Fix UAF in qfq_dequeue() #59

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2 changes: 1 addition & 1 deletion net/sched/sch_plug.c
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Original file line number Diff line number Diff line change
Expand Up @@ -214,7 +214,7 @@ static struct Qdisc_ops plug_qdisc_ops __read_mostly = {
.priv_size = sizeof(struct plug_sched_data),
.enqueue = plug_enqueue,
.dequeue = plug_dequeue,
.peek = qdisc_peek_head,
.peek = qdisc_peek_dequeued,
.init = plug_init,
.change = plug_change,
.reset = qdisc_reset_queue,
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22 changes: 17 additions & 5 deletions net/sched/sch_qfq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -973,10 +973,13 @@ static void qfq_update_eligible(struct qfq_sched *q)
}

/* Dequeue head packet of the head class in the DRR queue of the aggregate. */
static void agg_dequeue(struct qfq_aggregate *agg,
struct qfq_class *cl, unsigned int len)
static struct sk_buff *agg_dequeue(struct qfq_aggregate *agg,
struct qfq_class *cl, unsigned int len)
{
qdisc_dequeue_peeked(cl->qdisc);
struct sk_buff *skb = qdisc_dequeue_peeked(cl->qdisc);

if (!skb)
return NULL;

cl->deficit -= (int) len;

Expand All @@ -986,6 +989,8 @@ static void agg_dequeue(struct qfq_aggregate *agg,
cl->deficit += agg->lmax;
list_move_tail(&cl->alist, &agg->active);
}

return skb;
}

static inline struct sk_buff *qfq_peek_skb(struct qfq_aggregate *agg,
Expand Down Expand Up @@ -1131,11 +1136,18 @@ static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
if (!skb)
return NULL;

qdisc_qstats_backlog_dec(sch, skb);
sch->q.qlen--;

skb = agg_dequeue(in_serv_agg, cl, len);

if (!skb) {
sch->q.qlen++;
return NULL;
}

qdisc_qstats_backlog_dec(sch, skb);
qdisc_bstats_update(sch, skb);

agg_dequeue(in_serv_agg, cl, len);
/* If lmax is lowered, through qfq_change_class, for a class
* owning pending packets with larger size than the new value
* of lmax, then the following condition may hold.
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