From: Eric Dumazet <edumazet@google.com> stable inclusion from stable-v6.6.94 commit b4e9bab6011b9559b7c157b16b91ae46d4d8c533 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ICJTA4 CVE: CVE-2025-38115 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 82ffbe7776d0ac084031f114167712269bf3d832 ] SFQ has an assumption of always being able to queue at least one packet. However, after the blamed commit, sch->q.len can be inflated by packets in sch->gso_skb, and an enqueue() on an empty SFQ qdisc can be followed by an immediate drop. Fix sfq_drop() to properly clear q->tail in this situation. Tested: ip netns add lb ip link add dev to-lb type veth peer name in-lb netns lb ethtool -K to-lb tso off # force qdisc to requeue gso_skb ip netns exec lb ethtool -K in-lb gro on # enable NAPI ip link set dev to-lb up ip -netns lb link set dev in-lb up ip addr add dev to-lb 192.168.20.1/24 ip -netns lb addr add dev in-lb 192.168.20.2/24 tc qdisc replace dev to-lb root sfq limit 100 ip netns exec lb netserver netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & netperf -H 192.168.20.2 -l 100 & Fixes: a53851e2c321 ("net: sched: explicit locking in gso_cpu fallback") Reported-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de> Closes: https://lore.kernel.org/netdev/9da42688-bfaa-4364-8797-e9271f3bdaef@hetzner-... Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com> Link: https://patch.msgid.link/20250606165127.3629486-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Wang Liang <wangliang74@huawei.com> --- net/sched/sch_sfq.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c index 60754f366ab7..2f51def0d5d9 100644 --- a/net/sched/sch_sfq.c +++ b/net/sched/sch_sfq.c @@ -310,7 +310,10 @@ static unsigned int sfq_drop(struct Qdisc *sch, struct sk_buff **to_free) /* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */ x = q->tail->next; slot = &q->slots[x]; - q->tail->next = slot->next; + if (slot->next == x) + q->tail = NULL; /* no more active slots */ + else + q->tail->next = slot->next; q->ht[slot->hash] = SFQ_EMPTY_SLOT; goto drop; } -- 2.34.1