[PATCH 4.19 62/63] net_sched: check cops->tcf_block in tc_bind_tclass()

[Greg Kroah-Hartman]

From: Cong Wang <xiyou.wangcong@xxxxxxxxx>

[ Upstream commit 8b142a00edcf8422ca48b8de88d286efb500cb53 ]

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@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
Cc: Jiri Pirko <jiri@xxxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 be7cd140b2a38..b06cc5e504127 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1831,6 +1831,8 @@ 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, NULL);
 	if (!block)
 		return;
-- 
2.20.1