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net_sched: let qdisc_put() accept NULL pointer

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[ 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 <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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Cong Wang 2019-09-12 10:22:30 -07:00 committed by Greg Kroah-Hartman
parent 717ad917f2
commit e0f600b69d
1 changed files with 5 additions and 1 deletions
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6
net/sched/sch_generic.c
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@ -703,7 +703,11 @@ static void qdisc_rcu_free(struct rcu_head *head)
void qdisc_destroy(struct Qdisc *qdisc)
{
const struct Qdisc_ops *ops = qdisc->ops;
const struct Qdisc_ops *ops;
if (!qdisc)
return;
ops = qdisc->ops;
if (qdisc->flags & TCQ_F_BUILTIN ||
!refcount_dec_and_test(&qdisc->refcnt))