From: Cong Wang <xiyou.wangcong@xxxxxxxxx>
[ 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@xxxxxxxxxxxxxxxxxxxxxxxxx
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
Cc: Jiri Pirko <jiri@xxxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Acked-by: Jiri Pirko <jiri@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sched/sch_generic.c | 3 +++
1 file changed, 3 insertions(+)
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -950,6 +950,9 @@ void qdisc_destroy(struct Qdisc *qdisc)
const struct Qdisc_ops *ops = qdisc->ops;
struct sk_buff *skb, *tmp;
+ if (!qdisc)
+ return;
+
if (qdisc->flags & TCQ_F_BUILTIN ||
!refcount_dec_and_test(&qdisc->refcnt))
return;
