From: WANG Cong <xiyou.wangcong@gmail.com>
Date: Wed, 5 Apr 2017 01:51:30 +0000 (-0700)
Subject: net_sched: check noop_qdisc before qdisc_hash_add()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=92f9170621a13e4ba4eda6dfb070318d5405a0cf;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

net_sched: check noop_qdisc before qdisc_hash_add()

Dmitry reported a crash when injecting faults in
attach_one_default_qdisc() and dev->qdisc is still
a noop_disc, the check before qdisc_hash_add() fails
to catch it because it tests NULL. We should test
against noop_qdisc since it is the default qdisc
at this point.

Fixes: 59cc1f61f09c ("net: sched: convert qdisc linked list to hashtable")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index b052b27a984e..1a2f9e964330 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -794,7 +794,7 @@ static void attach_default_qdiscs(struct net_device *dev)
 		}
 	}
 #ifdef CONFIG_NET_SCHED
-	if (dev->qdisc)
+	if (dev->qdisc != &noop_qdisc)
 		qdisc_hash_add(dev->qdisc);
 #endif
 }