From d38939ebe0d992d581acb6885c1723fa83c1fb2c Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Tue, 6 May 2025 21:35:58 -0700 Subject: [PATCH] net_sched: Flush gso_skb list too during ->change() [ Upstream commit 2d3cbfd6d54a2c39ce3244f33f85c595844bd7b8 ] Previously, when reducing a qdisc's limit via the ->change() operation, only the main skb queue was trimmed, potentially leaving packets in the gso_skb list. This could result in NULL pointer dereference when we only check sch->limit against sch->q.qlen. This patch introduces a new helper, qdisc_dequeue_internal(), which ensures both the gso_skb list and the main queue are properly flushed when trimming excess packets. All relevant qdiscs (codel, fq, fq_codel, fq_pie, hhf, pie) are updated to use this helper in their ->change() routines. Fixes: 76e3cc126bb2 ("codel: Controlled Delay AQM") Fixes: 4b549a2ef4be ("fq_codel: Fair Queue Codel AQM") Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler") Fixes: ec97ecf1ebe4 ("net: sched: add Flow Queue PIE packet scheduler") Fixes: 10239edf86f1 ("net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc") Fixes: d4b36210c2e6 ("net: pkt_sched: PIE AQM scheme") Reported-by: Will Reported-by: Savy Signed-off-by: Cong Wang Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- include/net/sch_generic.h | 15 +++++++++++++++ net/sched/sch_codel.c | 2 +- net/sched/sch_fq.c | 2 +- net/sched/sch_fq_codel.c | 2 +- net/sched/sch_fq_pie.c | 2 +- net/sched/sch_hhf.c | 2 +- net/sched/sch_pie.c | 2 +- 7 files changed, 21 insertions(+), 6 deletions(-) diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 80f657bf2e047..b34e9e93a1463 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -997,6 +997,21 @@ static inline struct sk_buff *__qdisc_dequeue_head(struct qdisc_skb_head *qh) return skb; } +static inline struct sk_buff *qdisc_dequeue_internal(struct Qdisc *sch, bool direct) +{ + struct sk_buff *skb; + + skb = __skb_dequeue(&sch->gso_skb); + if (skb) { + sch->q.qlen--; + return skb; + } + if (direct) + return __qdisc_dequeue_head(&sch->q); + else + return sch->dequeue(sch); +} + static inline struct sk_buff *qdisc_dequeue_head(struct Qdisc *sch) { struct sk_buff *skb = __qdisc_dequeue_head(&sch->q); diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c index 5f2e068157456..63c02040b426a 100644 --- a/net/sched/sch_codel.c +++ b/net/sched/sch_codel.c @@ -168,7 +168,7 @@ static int codel_change(struct Qdisc *sch, struct nlattr *opt, qlen = sch->q.qlen; while (sch->q.qlen > sch->limit) { - struct sk_buff *skb = __qdisc_dequeue_head(&sch->q); + struct sk_buff *skb = qdisc_dequeue_internal(sch, true); dropped += qdisc_pkt_len(skb); qdisc_qstats_backlog_dec(sch, skb); diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c index f59a2cb2c803d..91f5ef6be0f23 100644 --- a/net/sched/sch_fq.c +++ b/net/sched/sch_fq.c @@ -901,7 +901,7 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt, sch_tree_lock(sch); } while (sch->q.qlen > sch->limit) { - struct sk_buff *skb = fq_dequeue(sch); + struct sk_buff *skb = qdisc_dequeue_internal(sch, false); if (!skb) break; diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c index 9330923a624c0..47b5a056165cb 100644 --- a/net/sched/sch_fq_codel.c +++ b/net/sched/sch_fq_codel.c @@ -431,7 +431,7 @@ static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt, while (sch->q.qlen > sch->limit || q->memory_usage > q->memory_limit) { - struct sk_buff *skb = fq_codel_dequeue(sch); + struct sk_buff *skb = qdisc_dequeue_internal(sch, false); q->cstats.drop_len += qdisc_pkt_len(skb); rtnl_kfree_skbs(skb, skb); diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c index 68e6acd0f130d..607c580d75e4b 100644 --- a/net/sched/sch_fq_pie.c +++ b/net/sched/sch_fq_pie.c @@ -357,7 +357,7 @@ static int fq_pie_change(struct Qdisc *sch, struct nlattr *opt, /* Drop excess packets if new limit is lower */ while (sch->q.qlen > sch->limit) { - struct sk_buff *skb = fq_pie_qdisc_dequeue(sch); + struct sk_buff *skb = qdisc_dequeue_internal(sch, false); len_dropped += qdisc_pkt_len(skb); num_dropped += 1; diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c index d26cd436cbe31..83fc44f20e31c 100644 --- a/net/sched/sch_hhf.c +++ b/net/sched/sch_hhf.c @@ -560,7 +560,7 @@ static int hhf_change(struct Qdisc *sch, struct nlattr *opt, qlen = sch->q.qlen; prev_backlog = sch->qstats.backlog; while (sch->q.qlen > sch->limit) { - struct sk_buff *skb = hhf_dequeue(sch); + struct sk_buff *skb = qdisc_dequeue_internal(sch, false); rtnl_kfree_skbs(skb, skb); } diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c index b60b31ef71cc5..e1bb151a97195 100644 --- a/net/sched/sch_pie.c +++ b/net/sched/sch_pie.c @@ -190,7 +190,7 @@ static int pie_change(struct Qdisc *sch, struct nlattr *opt, /* Drop excess packets if new limit is lower */ qlen = sch->q.qlen; while (sch->q.qlen > sch->limit) { - struct sk_buff *skb = __qdisc_dequeue_head(&sch->q); + struct sk_buff *skb = qdisc_dequeue_internal(sch, true); dropped += qdisc_pkt_len(skb); qdisc_qstats_backlog_dec(sch, skb);