From: Stephen Hemminger <stephen@networkplumber.org> stable inclusion from stable-v5.10.226 commit 98c75d76187944296068d685dfd8a1e9fd8c4fdc category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IARX29 CVE: CVE-2024-46800 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 3b3a2a9c6349e25a025d2330f479bc33a6ccb54a upstream. If netem_dequeue() enqueues packet to inner qdisc and that qdisc returns __NET_XMIT_STOLEN. The packet is dropped but qdisc_tree_reduce_backlog() is not called to update the parent's q.qlen, leading to the similar use-after-free as Commit e04991a48dbaf382 ("netem: fix return value if duplicate enqueue fails") Commands to trigger KASAN UaF: ip link add type dummy ip link set lo up ip link set dummy0 up tc qdisc add dev lo parent root handle 1: drr tc filter add dev lo parent 1: basic classid 1:1 tc class add dev lo classid 1:1 drr tc qdisc add dev lo parent 1:1 handle 2: netem tc qdisc add dev lo parent 2: handle 3: drr tc filter add dev lo parent 3: basic classid 3:1 action mirred egress redirect dev dummy0 tc class add dev lo classid 3:1 drr ping -c1 -W0.01 localhost # Trigger bug tc class del dev lo classid 1:1 tc class add dev lo classid 1:1 drr ping -c1 -W0.01 localhost # UaF Fixes: 50612537e9ab ("netem: fix classful handling") Reported-by: Budimir Markovic <markovicbudimir@gmail.com> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Link: https://patch.msgid.link/20240901182438.4992-1-stephen@networkplumber.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Wang Liang <wangliang74@huawei.com> --- net/sched/sch_netem.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index b72b308fe406..8321ab36357c 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -722,11 +722,10 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch) err = qdisc_enqueue(skb, q->qdisc, &to_free); kfree_skb_list(to_free); - if (err != NET_XMIT_SUCCESS && - net_xmit_drop_count(err)) { - qdisc_qstats_drop(sch); - qdisc_tree_reduce_backlog(sch, 1, - pkt_len); + if (err != NET_XMIT_SUCCESS) { + if (net_xmit_drop_count(err)) + qdisc_qstats_drop(sch); + qdisc_tree_reduce_backlog(sch, 1, pkt_len); } goto tfifo_dequeue; } -- 2.34.1