From d38939ebe0d992d581acb6885c1723fa83c1fb2c Mon Sep 17 00:00:00 2001
From: Cong Wang <xiyou.wangcong@gmail.com>
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 <willsroot@protonmail.com>
Reported-by: Savy <savy@syst3mfailure.io>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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);