From 4c641342d70c413421a4175895fdbb44c3de53da Mon Sep 17 00:00:00 2001 From: Jia-Ju Bai Date: Mon, 29 Jul 2019 16:24:33 +0800 Subject: [PATCH] net: sched: Fix a possible null-pointer dereference in dequeue_func() [ Upstream commit 051c7b39be4a91f6b7d8c4548444e4b850f1f56c ] 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: 76e3cc126bb2 ("codel: Controlled Delay AQM") Signed-off-by: Jia-Ju Bai Reviewed-by: Jiri Pirko Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/sched/sch_codel.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c index 9b7e2980ee5c..3bc5dec3b17b 100644 --- a/net/sched/sch_codel.c +++ b/net/sched/sch_codel.c @@ -68,7 +68,8 @@ static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch) { struct sk_buff *skb = __skb_dequeue(&sch->q); - prefetch(&skb->end); /* we'll need skb_shinfo() */ + if (skb) + prefetch(&skb->end); /* we'll need skb_shinfo() */ return skb; }