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 <[email protected]> Fixes: ec97ecf ("net: sched: add Flow Queue PIE packet scheduler") Signed-off-by: Dan Carpenter <[email protected]> Acked-by: Cong Wang <[email protected]> Signed-off-by: David S. Miller <[email protected]>
kmaincent · Feb 6, 2020 · 7a02ea6 · 7a02ea6
1 parent 86b18aa
commit 7a02ea6
Showing 1 changed file with 1 addition and 1 deletion.
diff --git 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);