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+d5870a903591faaca...@syzkaller.appspotmail.com
Suggested-by: Linus Torvalds <torva...@linux-foundation.org>
Cc: Jamal Hadi Salim <j...@mojatatu.com>
Cc: Jiri Pirko <j...@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
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 ac28f6a5d70e..17bd8f539bc7 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;
--
2.21.0
