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From: Jiri Pirko <jiri@resnulli.us>
To: Jia-Ju Bai <baijiaju1990@gmail.com>
Cc: jhs@mojatatu.com, xiyou.wangcong@gmail.com, davem@davemloft.net,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: sched: Fix a possible null-pointer dereference in dequeue_func()
Date: Mon, 29 Jul 2019 08:56:53 +0200	[thread overview]
Message-ID: <20190729065653.GA2211@nanopsycho> (raw)
In-Reply-To: <20190729022157.18090-1-baijiaju1990@gmail.com>

Mon, Jul 29, 2019 at 04:21:57AM CEST, baijiaju1990@gmail.com wrote:
>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.
>
>Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>

Fixes tag, please?


>---
> net/sched/sch_codel.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
>index 25ef172c23df..30169b3adbbb 100644
>--- a/net/sched/sch_codel.c
>+++ b/net/sched/sch_codel.c
>@@ -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() */
>+		prefetch(&skb->end); /* we'll need skb_shinfo() */
>+	}
> 	return skb;
> }
> 
>-- 
>2.17.0
>

  reply	other threads:[~2019-07-29  6:56 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-29  2:21 [PATCH] net: sched: Fix a possible null-pointer dereference in dequeue_func() Jia-Ju Bai
2019-07-29  6:56 ` Jiri Pirko [this message]
2019-07-29  7:32   ` Jia-Ju Bai
2019-07-29  7:41     ` Jiri Pirko
2019-07-29  7:59       ` Jia-Ju Bai

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