From 7a02ea65027523386ab4ba4af0ab93497b3073df Mon Sep 17 00:00:00 2001 From: Dan Carpenter Date: Wed, 5 Feb 2020 14:53:30 +0300 Subject: [PATCH] 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 Fixes: ec97ecf1ebe4 ("net: sched: add Flow Queue PIE packet scheduler") Signed-off-by: Dan Carpenter Acked-by: Cong Wang Signed-off-by: David S. Miller --- net/sched/sch_fq_pie.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c index bbd0dea6b6b9..214657eb3dfd 100644 --- a/net/sched/sch_fq_pie.c +++ b/net/sched/sch_fq_pie.c @@ -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);