!1529 net/sched: sch_qfq: account for stab overhead in qfq_enqueue

Merge Pull Request from: @ci-robot 
 
PR sync from: Zhengchao Shao <shaozhengchao@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/WXOHRQHPIRWXZTKJ26Z6FSX2AX7ALOWX/ 
 
https://gitee.com/src-openeuler/kernel/issues/I7N3MX 
 
Link:https://gitee.com/openeuler/kernel/pulls/1529 

Reviewed-by: Yue Haibing <yuehaibing@huawei.com> 
Signed-off-by: Liu YongQiang <liuyongqiang13@huawei.com> 

net/sched/sch_qfq.c

@@ -116,6 +116,7 @@
 
 #define QFQ_MTU_SHIFT		16	/* to support TSO/GSO */
 #define QFQ_MIN_LMAX		512	/* see qfq_slot_insert */
+#define QFQ_MAX_LMAX		(1UL << QFQ_MTU_SHIFT)
 
 #define QFQ_MAX_AGG_CLASSES	8 /* max num classes per aggregate allowed */
 
@@ -387,8 +388,13 @@ static int qfq_change_agg(struct Qdisc *sch, struct qfq_class *cl, u32 weight,
 			   u32 lmax)
 {
 	struct qfq_sched *q = qdisc_priv(sch);
-	struct qfq_aggregate *new_agg = qfq_find_agg(q, lmax, weight);
+	struct qfq_aggregate *new_agg;
 
+	/* 'lmax' can range from [QFQ_MIN_LMAX, pktlen + stab overhead] */
+	if (lmax > QFQ_MAX_LMAX)
+		return -EINVAL;
+
+	new_agg = qfq_find_agg(q, lmax, weight);
 	if (new_agg == NULL) { /* create new aggregate */
 		new_agg = kzalloc(sizeof(*new_agg), GFP_ATOMIC);
 		if (new_agg == NULL)