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

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[ 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 <baijiaju1990@gmail.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jia-Ju Bai 2019-07-29 16:24:33 +08:00 committed by Greg Kroah-Hartman
parent 03eb042dec
commit 4c6f0d6ba0
1 changed files with 3 additions and 3 deletions
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6
net/sched/sch_codel.c
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@ -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;
}