linux/net/sched
Victor Nogueira 43d9a530c8 net/sched: ets: Remove drr class from the active list if it changes to strict
[ Upstream commit b1e125ae42 ]

Whenever a user issues an ets qdisc change command, transforming a
drr class into a strict one, the ets code isn't checking whether that
class was in the active list and removing it. This means that, if a
user changes a strict class (which was in the active list) back to a drr
one, that class will be added twice to the active list [1].

Doing so with the following commands:

tc qdisc add dev lo root handle 1: ets bands 2 strict 1
tc qdisc add dev lo parent 1:2 handle 20: \
    tbf rate 8bit burst 100b latency 1s
tc filter add dev lo parent 1: basic classid 1:2
ping -c1 -W0.01 -s 56 127.0.0.1
tc qdisc change dev lo root handle 1: ets bands 2 strict 2
tc qdisc change dev lo root handle 1: ets bands 2 strict 1
ping -c1 -W0.01 -s 56 127.0.0.1

Will trigger the following splat with list debug turned on:

[   59.279014][  T365] ------------[ cut here ]------------
[   59.279452][  T365] list_add double add: new=ffff88801d60e350, prev=ffff88801d60e350, next=ffff88801d60e2c0.
[   59.280153][  T365] WARNING: CPU: 3 PID: 365 at lib/list_debug.c:35 __list_add_valid_or_report+0x17f/0x220
[   59.280860][  T365] Modules linked in:
[   59.281165][  T365] CPU: 3 UID: 0 PID: 365 Comm: tc Not tainted 6.18.0-rc7-00105-g7e9f13163c13-dirty #239 PREEMPT(voluntary)
[   59.281977][  T365] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   59.282391][  T365] RIP: 0010:__list_add_valid_or_report+0x17f/0x220
[   59.282842][  T365] Code: 89 c6 e8 d4 b7 0d ff 90 0f 0b 90 90 31 c0 e9 31 ff ff ff 90 48 c7 c7 e0 a0 22 9f 48 89 f2 48 89 c1 4c 89 c6 e8 b2 b7 0d ff 90 <0f> 0b 90 90 31 c0 e9 0f ff ff ff 48 89 f7 48 89 44 24 10 4c 89 44
...
[   59.288812][  T365] Call Trace:
[   59.289056][  T365]  <TASK>
[   59.289224][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5
[   59.289546][  T365]  ets_qdisc_change+0xd2b/0x1e80
[   59.289891][  T365]  ? __lock_acquire+0x7e7/0x1be0
[   59.290223][  T365]  ? __pfx_ets_qdisc_change+0x10/0x10
[   59.290546][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5
[   59.290898][  T365]  ? __mutex_trylock_common+0xda/0x240
[   59.291228][  T365]  ? __pfx___mutex_trylock_common+0x10/0x10
[   59.291655][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5
[   59.291993][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5
[   59.292313][  T365]  ? trace_contention_end+0xc8/0x110
[   59.292656][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5
[   59.293022][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5
[   59.293351][  T365]  tc_modify_qdisc+0x63a/0x1cf0

Fix this by always checking and removing an ets class from the active list
when changing it to strict.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/tree/net/sched/sch_ets.c?id=ce052b9402e461a9aded599f5b47e76bc727f7de#n663

Fixes: cd9b50adc6 ("net/sched: ets: fix crash when flipping from 'strict' to 'quantum'")
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Link: https://patch.msgid.link/20251208190125.1868423-1-victor@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-01-02 12:56:47 +01:00
..
act_api.c net_sched: act: remove tcfa_qstats 2025-09-02 15:52:24 -07:00
act_bpf.c bpf: Add bpf_prog_run_data_pointers() 2025-11-14 08:56:49 -08:00
act_connmark.c net: sched: act_connmark: initialize struct tc_ife to fix kernel leak 2025-11-11 15:00:08 +01:00
act_csum.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
act_ct.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
act_ctinfo.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
act_gact.c net/sched: Add module aliases for cls_,sch_,act_ modules 2024-02-02 10:57:55 -08:00
act_gate.c net/sched: Switch to use hrtimer_setup() 2025-02-18 10:35:44 +01:00
act_ife.c net: sched: act_ife: initialize struct tc_ife to fix KMSAN kernel-infoleak 2025-11-11 15:00:08 +01:00
act_meta_mark.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
act_meta_skbprio.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
act_meta_skbtcindex.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
act_mirred.c net/sched: act_mirred: Move the recursion counter struct netdev_xmit 2025-05-15 15:23:31 +02:00
act_mpls.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
act_nat.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
act_pedit.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
act_police.c net_sched: act_police: use RCU in tcf_police_dump() 2025-07-11 16:01:17 -07:00
act_sample.c net: sched: act_sample: add action cookie to sample 2024-07-05 17:45:47 -07:00
act_simple.c net/sched: Remove redundant memset(0) call in reset_policy() 2025-08-12 17:13:29 -07:00
act_skbedit.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
act_skbmod.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
act_tunnel_key.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
act_vlan.c net_sched: add back BH safety to tcf_lock 2025-09-02 15:51:45 -07:00
bpf_qdisc.c bpf: Clean up individual BTF_ID code 2025-07-16 18:34:42 -07:00
cls_api.c tc: Ensure we have enough buffer space when sending filter netlink notifications 2025-04-08 13:57:49 +02:00
cls_basic.c net/sched: Add module aliases for cls_,sch_,act_ modules 2024-02-02 10:57:55 -08:00
cls_bpf.c bpf: Add bpf_prog_run_data_pointers() 2025-11-14 08:56:49 -08:00
cls_cgroup.c net/sched: Add module aliases for cls_,sch_,act_ modules 2024-02-02 10:57:55 -08:00
cls_flow.c treewide, timers: Rename from_timer() to timer_container_of() 2025-06-08 09:07:37 +02:00
cls_flower.c net: fix geneve_opt length integer overflow 2025-04-03 15:47:35 -07:00
cls_fw.c net/sched: Add module aliases for cls_,sch_,act_ modules 2024-02-02 10:57:55 -08:00
cls_matchall.c net: sched: refine software bypass handling in tc_run 2025-01-20 09:21:27 +00:00
cls_route.c net/sched: Add module aliases for cls_,sch_,act_ modules 2024-02-02 10:57:55 -08:00
cls_u32.c net: sched: refine software bypass handling in tc_run 2025-01-20 09:21:27 +00:00
em_canid.c net/sched: em_canid: fix uninit-value in em_canid_match 2025-11-26 16:28:10 +01:00
em_cmp.c net: sched: fix TCF_LAYER_TRANSPORT handling in tcf_get_base_ptr() 2025-11-24 18:53:14 -08:00
em_ipset.c sched: consistently handle layer3 header accesses in the presence of VLANs 2020-07-03 14:34:53 -07:00
em_ipt.c sched: consistently handle layer3 header accesses in the presence of VLANs 2020-07-03 14:34:53 -07:00
em_meta.c net: dismiss sk_forward_alloc_get() 2025-02-19 19:05:28 -08:00
em_nbyte.c net: sched: fix TCF_LAYER_TRANSPORT handling in tcf_get_base_ptr() 2025-11-24 18:53:14 -08:00
em_text.c net: sched: fix TCF_LAYER_TRANSPORT handling in tcf_get_base_ptr() 2025-11-24 18:53:14 -08:00
em_u32.c net: fill in MODULE_DESCRIPTION()s for net/sched 2024-02-09 14:12:02 -08:00
ematch.c net_sched: reject TCF_EM_SIMPLE case for complex ematch module 2022-12-19 09:43:18 +00:00
Kconfig sched: Add enqueue/dequeue of dualpi2 qdisc 2025-07-23 17:52:07 -07:00
Makefile sched: Add enqueue/dequeue of dualpi2 qdisc 2025-07-23 17:52:07 -07:00
sch_api.c net/sched: Abort __tc_modify_qdisc if parent is a clsact/ingress qdisc 2025-11-10 16:57:56 -08:00
sch_blackhole.c Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" 2020-07-16 16:48:34 -07:00
sch_cake.c net/sched: sch_cake: Fix incorrect qlen reduction in cake_drop 2025-12-18 14:03:31 +01:00
sch_cbs.c net/sched: cbs: Fix integer overflow in cbs_set_port_rate() 2024-10-15 18:25:47 -07:00
sch_choke.c net: sched: fix ordering of qlen adjustment 2024-12-04 12:54:22 +00:00
sch_codel.c net/sched: Fix backlog accounting in qdisc_dequeue_internal 2025-08-14 17:52:29 -07:00
sch_drr.c net_sched: drr: Fix double list add in class with netem as child qdisc 2025-04-28 15:55:06 -07:00
sch_dualpi2.c net/sched: sch_dualpi2: Run prob update timer in softirq to avoid deadlock 2025-08-19 17:49:01 -07:00
sch_etf.c net_sched: sch_tfs: implement lockless etf_dump() 2024-04-19 11:34:07 +01:00
sch_ets.c net/sched: ets: Remove drr class from the active list if it changes to strict 2026-01-02 12:56:47 +01:00
sch_fifo.c pfifo_tail_enqueue: Drop new packet when sch->limit == 0 2025-02-05 18:13:58 -08:00
sch_fq.c net/sched: Fix backlog accounting in qdisc_dequeue_internal 2025-08-14 17:52:29 -07:00
sch_fq_codel.c net/sched: Fix backlog accounting in qdisc_dequeue_internal 2025-08-14 17:52:29 -07:00
sch_fq_pie.c net/sched: Fix backlog accounting in qdisc_dequeue_internal 2025-08-14 17:52:29 -07:00
sch_frag.c net/sched: Use nested-BH locking for sch_frag_data_storage 2025-05-15 15:23:31 +02:00
sch_generic.c net_sched: limit try_bulk_dequeue_skb() batches 2025-11-11 17:56:50 -08:00
sch_gred.c sched: address a potential NULL pointer dereference in the GRED scheduler. 2025-03-06 16:35:14 -08:00
sch_hfsc.c net/sched: sch_qfq: Fix null-deref in agg_dequeue 2025-07-10 11:08:35 +02:00
sch_hhf.c net/sched: Fix backlog accounting in qdisc_dequeue_internal 2025-08-14 17:52:29 -07:00
sch_htb.c net/sched: Remove unnecessary WARNING condition for empty child qdisc in htb_activate 2025-08-20 19:27:08 -07:00
sch_ingress.c bpf: Fix too early release of tcx_entry 2024-07-08 14:07:31 -07:00
sch_mq.c net: sched: add rcu annotations around qdisc->qdisc_sleeping 2023-06-07 10:25:39 +01:00
sch_mqprio.c net/sched: mqprio: fix stack out-of-bounds write in tc entry parsing 2025-08-04 17:22:20 -07:00
sch_mqprio_lib.c net: sched: Fill in missing MODULE_DESCRIPTION for qdiscs 2023-11-01 21:49:09 -07:00
sch_mqprio_lib.h net/sched: mqprio: allow per-TC user input of FP adminStatus 2023-04-13 22:22:10 -07:00
sch_multiq.c net: sched: sch_multiq: fix possible OOB write in multiq_tune() 2024-06-05 10:50:19 +01:00
sch_netem.c net/sched: Restrict conditions for adding duplicating netems to qdisc tree 2025-07-11 15:50:21 -07:00
sch_pie.c net/sched: Fix backlog accounting in qdisc_dequeue_internal 2025-08-14 17:52:29 -07:00
sch_plug.c net/sched: Add module aliases for cls_,sch_,act_ modules 2024-02-02 10:57:55 -08:00
sch_prio.c net_sched: prio: fix a race in prio_tune() 2025-06-12 08:05:49 -07:00
sch_qfq.c net/sched: sch_qfq: Avoid triggering might_sleep in atomic context in qfq_delete_class 2025-07-22 11:48:34 +02:00
sch_red.c Including fixes from bluetooth and wireless. 2025-06-12 09:50:36 -07:00
sch_sfb.c net/sched: Add drop reasons for AQM-based qdiscs 2024-12-17 13:27:29 +01:00
sch_sfq.c Including fixes from bluetooth and wireless. 2025-06-12 09:50:36 -07:00
sch_skbprio.c net_sched: skbprio: Remove overly strict queue assertions 2025-04-02 16:03:32 -07:00
sch_taprio.c net/sched: taprio: enforce minimum value for picos_per_byte 2025-08-01 15:15:28 -07:00
sch_tbf.c net_sched: tbf: fix a race in tbf_change() 2025-06-12 08:05:50 -07:00
sch_teql.c net: annotate writes on dev->mtu from ndo_change_mtu() 2024-05-07 16:19:14 -07:00