From 6efb971ba8edfbd80b666f29de12882852f095ae Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Thu, 12 Sep 2019 10:22:30 -0700 Subject: [PATCH] net_sched: let qdisc_put() accept NULL pointer 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 --- net/sched/sch_generic.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index ac28f6a..17bd8f5 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -985,6 +985,9 @@ static void qdisc_destroy(struct Qdisc *qdisc) void qdisc_put(struct Qdisc *qdisc) { + if (!qdisc) + return; + if (qdisc->flags & TCQ_F_BUILTIN || !refcount_dec_and_test(&qdisc->refcnt)) return; -- 2.7.4