From b9307234e7fbffa0b22735c660e522d217b8fe52 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Sat, 21 Sep 2019 21:14:17 +0800 Subject: [PATCH] net_sched: let qdisc_put() accept NULL pointer [ Upstream commit 6efb971ba8edfbd80b666f29de12882852f095ae ] 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 Cc: Jamal Hadi Salim Cc: Jiri Pirko Signed-off-by: Cong Wang Acked-by: Jiri Pirko Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yang Yingliang --- net/sched/sch_generic.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 875f521bce0d..30e32df5f84a 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -947,9 +947,13 @@ void qdisc_free(struct Qdisc *qdisc) void qdisc_destroy(struct Qdisc *qdisc) { - const struct Qdisc_ops *ops = qdisc->ops; + const struct Qdisc_ops *ops; struct sk_buff *skb, *tmp; + if (!qdisc) + return; + ops = qdisc->ops; + if (qdisc->flags & TCQ_F_BUILTIN || !refcount_dec_and_test(&qdisc->refcnt)) return; -- GitLab