From 54b9f5791846d2de59e8c65502b3f1071f65424f Mon Sep 17 00:00:00 2001
From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Thu, 31 Oct 2019 11:42:59 -0700
Subject: [PATCH] net_sched: check cops->tcf_block in tc_bind_tclass()

commit 8b142a00edcf8422ca48b8de88d286efb500cb53 upstream

At least sch_red and sch_tbf don't implement ->tcf_block()
while still have a non-zero tc "class".

Instead of adding nop implementations to each of such qdisc's,
we can just relax the check of cops->tcf_block() in
tc_bind_tclass(). They don't support TC filter anyway.

Reported-by: syzbot+21b29db13c065852f64b@syzkaller.appspotmail.com
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zubin Mithra <zsm@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/sched/sch_api.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 637949b576c6..296e95f72eb1 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1695,6 +1695,8 @@ static void tc_bind_tclass(struct Qdisc *q, u32 portid, u32 clid,
 	cl = cops->find(q, portid);
 	if (!cl)
 		return;
+	if (!cops->tcf_block)
+		return;
 	block = cops->tcf_block(q, cl);
 	if (!block)
 		return;