Fixes qfq_change_class() error case. cl->qdisc and cl should only be freed if a new class and qdisc were allocated, or we risk various UAF. Fixes: 462dbc9101ac ("pkt_sched: QFQ Plus: fair-queueing service at DRR cost") Reported-by: syzbot+07f3f38f723c335f106d@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6965351d.050a0220.eaf7.00c5.GAE@google.com/T/#u Signed-off-by: Eric Dumazet --- net/sched/sch_qfq.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c index f4013b547438ffe1bdc8ba519971a1681df4700b..9d59090bbe934ad56ab08a59708aab375aa77cf0 100644 --- a/net/sched/sch_qfq.c +++ b/net/sched/sch_qfq.c @@ -529,8 +529,10 @@ static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid, return 0; destroy_class: - qdisc_put(cl->qdisc); - kfree(cl); + if (!existing) { + qdisc_put(cl->qdisc); + kfree(cl); + } return err; } -- 2.52.0.457.g6b5491de43-goog