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net_sched: Flush gso_skb list too during ->change()

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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: 76e3cc126b ("codel: Controlled Delay AQM")
Fixes: 4b549a2ef4 ("fq_codel: Fair Queue Codel AQM")
Fixes: afe4fd0624 ("pkt_sched: fq: Fair Queue packet scheduler")
Fixes: ec97ecf1eb ("net: sched: add Flow Queue PIE packet scheduler")
Fixes: 10239edf86 ("net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc")
Fixes: d4b36210c2 ("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>
This commit is contained in:
Cong Wang 2025-05-06 21:35:58 -07:00 committed by David S. Miller
parent 6b3ab7f2cb
commit 2d3cbfd6d5
7 changed files with 21 additions and 6 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

15
include/net/sch_generic.h
View file

@ -1031,6 +1031,21 @@ 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);

2
net/sched/sch_codel.c
View file

@ -144,7 +144,7 @@ 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);

2
net/sched/sch_fq.c
View file

@ -1136,7 +1136,7 @@ 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;

2
net/sched/sch_fq_codel.c
View file

@ -441,7 +441,7 @@ 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);

2
net/sched/sch_fq_pie.c
View file

@ -366,7 +366,7 @@ 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;

2
net/sched/sch_hhf.c
View file

@ -564,7 +564,7 @@ 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);
}

2
net/sched/sch_pie.c
View file

@ -195,7 +195,7 @@ 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);