From 2d3cbfd6d54a2c39ce3244f33f85c595844bd7b8 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Tue, 6 May 2025 21:35:58 -0700 Subject: [PATCH 1/2] net_sched: Flush gso_skb list too during ->change() 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 --- 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 d48c657191cd..1c05fed05f2b 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -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); diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c index 12dd71139da3..c93761040c6e 100644 --- a/net/sched/sch_codel.c +++ b/net/sched/sch_codel.c @@ -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); diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c index 2ca5332cfcc5..902ff5470607 100644 --- a/net/sched/sch_fq.c +++ b/net/sched/sch_fq.c @@ -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; diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c index 6c9029f71e88..2a0f3a513bfa 100644 --- a/net/sched/sch_fq_codel.c +++ b/net/sched/sch_fq_codel.c @@ -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); diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c index f3b8203d3e85..df7fac95ab15 100644 --- a/net/sched/sch_fq_pie.c +++ b/net/sched/sch_fq_pie.c @@ -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; diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c index 44d9efe1a96a..5aa434b46707 100644 --- a/net/sched/sch_hhf.c +++ b/net/sched/sch_hhf.c @@ -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); } diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c index 3771d000b30d..ff49a6c97033 100644 --- a/net/sched/sch_pie.c +++ b/net/sched/sch_pie.c @@ -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); From 16ce349b15069334710faa10f2e09866f8391f26 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Tue, 6 May 2025 21:35:59 -0700 Subject: [PATCH 2/2] selftests/tc-testing: Add qdisc limit trimming tests Added new test cases for FQ, FQ_CODEL, FQ_PIE, and HHF qdiscs to verify queue trimming behavior when the qdisc limit is dynamically reduced. Each test injects packets, reduces the qdisc limit, and checks that the new limit is enforced. This is still best effort since timing qdisc backlog is not easy. Signed-off-by: Cong Wang Signed-off-by: David S. Miller --- .../tc-testing/tc-tests/qdiscs/codel.json | 24 +++++++++++++++++++ .../tc-testing/tc-tests/qdiscs/fq.json | 22 +++++++++++++++++ .../tc-testing/tc-tests/qdiscs/fq_codel.json | 22 +++++++++++++++++ .../tc-testing/tc-tests/qdiscs/fq_pie.json | 22 +++++++++++++++++ .../tc-testing/tc-tests/qdiscs/hhf.json | 22 +++++++++++++++++ .../tc-testing/tc-tests/qdiscs/pie.json | 24 +++++++++++++++++++ 6 files changed, 136 insertions(+) create mode 100644 tools/testing/selftests/tc-testing/tc-tests/qdiscs/pie.json diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/codel.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/codel.json index e9469ee71e6f..6d515d0e5ed6 100644 --- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/codel.json +++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/codel.json @@ -189,5 +189,29 @@ "teardown": [ "$TC qdisc del dev $DUMMY handle 1: root" ] + }, + { + "id": "deb1", + "name": "CODEL test qdisc limit trimming", + "category": ["qdisc", "codel"], + "plugins": { + "requires": ["nsPlugin", "scapyPlugin"] + }, + "setup": [ + "$TC qdisc add dev $DEV1 handle 1: root codel limit 10" + ], + "scapy": [ + { + "iface": "$DEV0", + "count": 10, + "packet": "Ether(type=0x800)/IP(src='10.0.0.10',dst='10.0.0.20')/TCP(sport=5000,dport=10)" + } + ], + "cmdUnderTest": "$TC qdisc change dev $DEV1 handle 1: root codel limit 1", + "expExitCode": "0", + "verifyCmd": "$TC qdisc show dev $DEV1", + "matchPattern": "qdisc codel 1: root refcnt [0-9]+ limit 1p target 5ms interval 100ms", + "matchCount": "1", + "teardown": ["$TC qdisc del dev $DEV1 handle 1: root"] } ] diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json index 3a537b2ec4c9..24faf4e12dfa 100644 --- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json +++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq.json @@ -377,5 +377,27 @@ "teardown": [ "$TC qdisc del dev $DUMMY handle 1: root" ] + }, + { + "id": "9479", + "name": "FQ test qdisc limit trimming", + "category": ["qdisc", "fq"], + "plugins": {"requires": ["nsPlugin", "scapyPlugin"]}, + "setup": [ + "$TC qdisc add dev $DEV1 handle 1: root fq limit 10" + ], + "scapy": [ + { + "iface": "$DEV0", + "count": 10, + "packet": "Ether(type=0x800)/IP(src='10.0.0.10',dst='10.0.0.20')/TCP(sport=5000,dport=10)" + } + ], + "cmdUnderTest": "$TC qdisc change dev $DEV1 handle 1: root fq limit 1", + "expExitCode": "0", + "verifyCmd": "$TC qdisc show dev $DEV1", + "matchPattern": "qdisc fq 1: root refcnt [0-9]+ limit 1p", + "matchCount": "1", + "teardown": ["$TC qdisc del dev $DEV1 handle 1: root"] } ] diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_codel.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_codel.json index 9774b1e8801b..4ce62b857fd7 100644 --- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_codel.json +++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_codel.json @@ -294,5 +294,27 @@ "teardown": [ "$TC qdisc del dev $DUMMY handle 1: root" ] + }, + { + "id": "0436", + "name": "FQ_CODEL test qdisc limit trimming", + "category": ["qdisc", "fq_codel"], + "plugins": {"requires": ["nsPlugin", "scapyPlugin"]}, + "setup": [ + "$TC qdisc add dev $DEV1 handle 1: root fq_codel limit 10" + ], + "scapy": [ + { + "iface": "$DEV0", + "count": 10, + "packet": "Ether(type=0x800)/IP(src='10.0.0.10',dst='10.0.0.20')/TCP(sport=5000,dport=10)" + } + ], + "cmdUnderTest": "$TC qdisc change dev $DEV1 handle 1: root fq_codel limit 1", + "expExitCode": "0", + "verifyCmd": "$TC qdisc show dev $DEV1", + "matchPattern": "qdisc fq_codel 1: root refcnt [0-9]+ limit 1p flows 1024 quantum.*target 5ms interval 100ms memory_limit 32Mb ecn drop_batch 64", + "matchCount": "1", + "teardown": ["$TC qdisc del dev $DEV1 handle 1: root"] } ] diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_pie.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_pie.json index d012d88d67fe..229fe1bf4a90 100644 --- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_pie.json +++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/fq_pie.json @@ -18,5 +18,27 @@ "matchCount": "1", "teardown": [ ] + }, + { + "id": "83bf", + "name": "FQ_PIE test qdisc limit trimming", + "category": ["qdisc", "fq_pie"], + "plugins": {"requires": ["nsPlugin", "scapyPlugin"]}, + "setup": [ + "$TC qdisc add dev $DEV1 handle 1: root fq_pie limit 10" + ], + "scapy": [ + { + "iface": "$DEV0", + "count": 10, + "packet": "Ether(type=0x800)/IP(src='10.0.0.10',dst='10.0.0.20')/TCP(sport=5000,dport=10)" + } + ], + "cmdUnderTest": "$TC qdisc change dev $DEV1 handle 1: root fq_pie limit 1", + "expExitCode": "0", + "verifyCmd": "$TC qdisc show dev $DEV1", + "matchPattern": "qdisc fq_pie 1: root refcnt [0-9]+ limit 1p", + "matchCount": "1", + "teardown": ["$TC qdisc del dev $DEV1 handle 1: root"] } ] diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/hhf.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/hhf.json index dbef5474b26b..0ca19fac54a5 100644 --- a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/hhf.json +++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/hhf.json @@ -188,5 +188,27 @@ "teardown": [ "$TC qdisc del dev $DUMMY handle 1: root" ] + }, + { + "id": "385f", + "name": "HHF test qdisc limit trimming", + "category": ["qdisc", "hhf"], + "plugins": {"requires": ["nsPlugin", "scapyPlugin"]}, + "setup": [ + "$TC qdisc add dev $DEV1 handle 1: root hhf limit 10" + ], + "scapy": [ + { + "iface": "$DEV0", + "count": 10, + "packet": "Ether(type=0x800)/IP(src='10.0.0.10',dst='10.0.0.20')/TCP(sport=5000,dport=10)" + } + ], + "cmdUnderTest": "$TC qdisc change dev $DEV1 handle 1: root hhf limit 1", + "expExitCode": "0", + "verifyCmd": "$TC qdisc show dev $DEV1", + "matchPattern": "qdisc hhf 1: root refcnt [0-9]+ limit 1p.*hh_limit 2048 reset_timeout 40ms admit_bytes 128Kb evict_timeout 1s non_hh_weight 2", + "matchCount": "1", + "teardown": ["$TC qdisc del dev $DEV1 handle 1: root"] } ] diff --git a/tools/testing/selftests/tc-testing/tc-tests/qdiscs/pie.json b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/pie.json new file mode 100644 index 000000000000..1a98b66e8030 --- /dev/null +++ b/tools/testing/selftests/tc-testing/tc-tests/qdiscs/pie.json @@ -0,0 +1,24 @@ +[ + { + "id": "6158", + "name": "PIE test qdisc limit trimming", + "category": ["qdisc", "pie"], + "plugins": {"requires": ["nsPlugin", "scapyPlugin"]}, + "setup": [ + "$TC qdisc add dev $DEV1 handle 1: root pie limit 10" + ], + "scapy": [ + { + "iface": "$DEV0", + "count": 10, + "packet": "Ether(type=0x800)/IP(src='10.0.0.10',dst='10.0.0.20')/TCP(sport=5000,dport=10)" + } + ], + "cmdUnderTest": "$TC qdisc change dev $DEV1 handle 1: root pie limit 1", + "expExitCode": "0", + "verifyCmd": "$TC qdisc show dev $DEV1", + "matchPattern": "qdisc pie 1: root refcnt [0-9]+ limit 1p", + "matchCount": "1", + "teardown": ["$TC qdisc del dev $DEV1 handle 1: root"] + } +]