From 3879cffd9d07aa0377c4b8835c4f64b4fb24ac78 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 12 Jan 2026 17:56:56 +0000 Subject: [PATCH] net/sched: sch_qfq: do not free existing class in qfq_change_class() 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 Reviewed-by: Jamal Hadi Salim Link: https://patch.msgid.link/20260112175656.17605-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- 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 f4013b547438f..9d59090bbe934 100644 --- a/net/sched/sch_qfq.c +++ b/net/sched/sch_qfq.c @@ -529,8 +529,10 @@ set_change_agg: return 0; destroy_class: - qdisc_put(cl->qdisc); - kfree(cl); + if (!existing) { + qdisc_put(cl->qdisc); + kfree(cl); + } return err; } -- 2.47.3