net_sched: drr: check for NULL pointer in drr_dequeue

There are cases where qdisc_dequeue_peeked can return NULL, and the result
is dereferenced later on in the function.

Similarly to the other qdisc dequeue functions, check whether the skb
pointer is NULL and if it is, goto out.

Signed-off-by: Bernie Harris <bernie.harris@alliedtelesis.co.nz>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
index f26bdea875c1a8413774e767bb897012d969d2e6..a1cd778240cd7f2b14336c26ba6eec282c1c60b6 100644 (file)
--- a/net/sched/sch_drr.c
+++ b/net/sched/sch_drr.c
@@ -403,6 +403,8 @@ static struct sk_buff *drr_dequeue(struct Qdisc *sch)
                if (len <= cl->deficit) {
                        cl->deficit -= len;
                        skb = qdisc_dequeue_peeked(cl->qdisc);
+                       if (unlikely(skb == NULL))
+                               goto out;
                        if (cl->qdisc->q.qlen == 0)
                                list_del(&cl->alist);