Commit 051c7b39 authored Jul 29, 2019 by Jia-Ju Bai Committed by David S. Miller Jul 29, 2019

net: sched: Fix a possible null-pointer dereference in dequeue_func()



In dequeue_func(), there is an if statement on line 74 to check whether
skb is NULL:
    if (skb)

When skb is NULL, it is used on line 77:
    prefetch(&skb->end);

Thus, a possible null-pointer dereference may occur.

To fix this bug, skb->end is used when skb is not NULL.

This bug is found by a static analysis tool STCheck written by us.

Fixes: 76e3cc12 ("codel: Controlled Delay AQM")
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent a7f9cbf0

net/sched/sch_codel.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -71,10 +71,10 @@ static struct sk_buff dequeue_func(struct codel_vars vars, void *ctx)
		struct Qdisc *sch = ctx;
		struct sk_buff *skb = __qdisc_dequeue_head(&sch->q);

		if (skb)
		if (skb) {
		sch->qstats.backlog -= qdisc_pkt_len(skb);

		prefetch(&skb->end); /* we'll need skb_shinfo() */
		}
		return skb;
		}

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