Commit 7a02ea65 authored Feb 05, 2020 by Dan Carpenter Committed by David S. Miller Feb 06, 2020

net: sched: prevent a use after free



The bug is that we call kfree_skb(skb) and then pass "skb" to
qdisc_pkt_len(skb) on the next line, which is a use after free.
Also Cong Wang points out that it's better to delay the actual
frees until we drop the rtnl lock so we should use rtnl_kfree_skbs()
instead of kfree_skb().

Cc: Cong Wang <xiyou.wangcong@gmail.com>
Fixes: ec97ecf1 ("net: sched: add Flow Queue PIE packet scheduler")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 86b18aaa

net/sched/sch_fq_pie.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -349,9 +349,9 @@ static int fq_pie_change(struct Qdisc sch, struct nlattr opt,
		while (sch->q.qlen > sch->limit) {
		struct sk_buff *skb = fq_pie_qdisc_dequeue(sch);

		kfree_skb(skb);
		len_dropped += qdisc_pkt_len(skb);
		num_dropped += 1;
		rtnl_kfree_skbs(skb, skb);
		}
		qdisc_tree_reduce_backlog(sch, num_dropped, len_dropped);

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