From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Thu, 12 Sep 2019 10:22:30 -0700
Subject: net_sched: let qdisc_put() accept NULL pointer
Patch-mainline: v5.4-rc1
Git-commit: 6efb971ba8edfbd80b666f29de12882852f095ae
References: bsc#1056657 FATE#322189 bsc#1056653 FATE#322190 bsc#1056787
When tcf_block_get() fails in sfb_init(), q->qdisc is still a NULL
pointer which leads to a crash in sfb_destroy(). Similar for
sch_dsmark.
Instead of fixing each separately, Linus suggested to just accept
NULL pointer in qdisc_put(), which would make callers easier.
(For sch_dsmark, the bug probably exists long before commit
6529eaba33f0.)
Fixes: 6529eaba33f0 ("net: sched: introduce tcf block infractructure")
Reported-by: syzbot+d5870a903591faaca4ae@syzkaller.appspotmail.com
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
net/sched/sch_generic.c | 3 +++
1 file changed, 3 insertions(+)
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1008,6 +1008,9 @@ static void qdisc_destroy(struct Qdisc *
void qdisc_put(struct Qdisc *qdisc)
{
+ if (!qdisc)
+ return;
+
if (qdisc->flags & TCQ_F_BUILTIN ||
!refcount_dec_and_test(&qdisc->refcnt))
return;