net_sched: sch_skbprio: add message validation to skbprio_change()

stable inclusion
from linux-4.19.123
commit 37e33f51a81677bad469294903fbdc812b4ae0c6

--------------------------------

[ Upstream commit 2761121a ]

Do not assume the attribute has the right size.

Fixes: aea5f654 ("net/sched: add skbprio scheduler")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Reported-by: Nsyzbot <syzkaller@googlegroups.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NLi Aichun <liaichun@huawei.com>
Reviewed-by: Nguodeqing <geffrey.guo@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/sched/sch_skbprio.c

@@ -173,6 +173,9 @@ static int skbprio_change(struct Qdisc *sch, struct nlattr *opt,
 {
 	struct tc_skbprio_qopt *ctl = nla_data(opt);
 
+	if (opt->nla_len != nla_attr_size(sizeof(*ctl)))
+		return -EINVAL;
+
 	sch->limit = ctl->limit;
 	return 0;
 }