linux/net/sched
Davide Caratti 87c6efc5ce net/sched: ets: use old 'nbands' while purging unused classes
Shuang reported sch_ets test-case [1] crashing in ets_class_qlen_notify()
after recent changes from Lion [2]. The problem is: in ets_qdisc_change()
we purge unused DWRR queues; the value of 'q->nbands' is the new one, and
the cleanup should be done with the old one. The problem is here since my
first attempts to fix ets_qdisc_change(), but it surfaced again after the
recent qdisc len accounting fixes. Fix it purging idle DWRR queues before
assigning a new value of 'q->nbands', so that all purge operations find a
consistent configuration:

 - old 'q->nbands' because it's needed by ets_class_find()
 - old 'q->nstrict' because it's needed by ets_class_is_strict()

 BUG: kernel NULL pointer dereference, address: 0000000000000000
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: Oops: 0000 [#1] SMP NOPTI
 CPU: 62 UID: 0 PID: 39457 Comm: tc Kdump: loaded Not tainted 6.12.0-116.el10.x86_64 #1 PREEMPT(voluntary)
 Hardware name: Dell Inc. PowerEdge R640/06DKY5, BIOS 2.12.2 07/09/2021
 RIP: 0010:__list_del_entry_valid_or_report+0x4/0x80
 Code: ff 4c 39 c7 0f 84 39 19 8e ff b8 01 00 00 00 c3 cc cc cc cc 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa <48> 8b 17 48 8b 4f 08 48 85 d2 0f 84 56 19 8e ff 48 85 c9 0f 84 ab
 RSP: 0018:ffffba186009f400 EFLAGS: 00010202
 RAX: 00000000000000d6 RBX: 0000000000000000 RCX: 0000000000000004
 RDX: ffff9f0fa29b69c0 RSI: 0000000000000000 RDI: 0000000000000000
 RBP: ffffffffc12c2400 R08: 0000000000000008 R09: 0000000000000004
 R10: ffffffffffffffff R11: 0000000000000004 R12: 0000000000000000
 R13: ffff9f0f8cfe0000 R14: 0000000000100005 R15: 0000000000000000
 FS:  00007f2154f37480(0000) GS:ffff9f269c1c0000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 00000001530be001 CR4: 00000000007726f0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 PKRU: 55555554
 Call Trace:
  <TASK>
  ets_class_qlen_notify+0x65/0x90 [sch_ets]
  qdisc_tree_reduce_backlog+0x74/0x110
  ets_qdisc_change+0x630/0xa40 [sch_ets]
  __tc_modify_qdisc.constprop.0+0x216/0x7f0
  tc_modify_qdisc+0x7c/0x120
  rtnetlink_rcv_msg+0x145/0x3f0
  netlink_rcv_skb+0x53/0x100
  netlink_unicast+0x245/0x390
  netlink_sendmsg+0x21b/0x470
  ____sys_sendmsg+0x39d/0x3d0
  ___sys_sendmsg+0x9a/0xe0
  __sys_sendmsg+0x7a/0xd0
  do_syscall_64+0x7d/0x160
  entry_SYSCALL_64_after_hwframe+0x76/0x7e
 RIP: 0033:0x7f2155114084
 Code: 89 02 b8 ff ff ff ff eb bb 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 80 3d 25 f0 0c 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 89 54 24 1c 48 89
 RSP: 002b:00007fff1fd7a988 EFLAGS: 00000202 ORIG_RAX: 000000000000002e
 RAX: ffffffffffffffda RBX: 0000560ec063e5e0 RCX: 00007f2155114084
 RDX: 0000000000000000 RSI: 00007fff1fd7a9f0 RDI: 0000000000000003
 RBP: 00007fff1fd7aa60 R08: 0000000000000010 R09: 000000000000003f
 R10: 0000560ee9b3a010 R11: 0000000000000202 R12: 00007fff1fd7aae0
 R13: 000000006891ccde R14: 0000560ec063e5e0 R15: 00007fff1fd7aad0
  </TASK>

 [1] https://lore.kernel.org/netdev/e08c7f4a6882f260011909a868311c6e9b54f3e4.1639153474.git.dcaratti@redhat.com/
 [2] https://lore.kernel.org/netdev/d912cbd7-193b-4269-9857-525bee8bbb6a@gmail.com/

Cc: stable@vger.kernel.org
Fixes: 103406b38c ("net/sched: Always pass notifications when child class becomes empty")
Fixes: c062f2a0b0 ("net/sched: sch_ets: don't remove idle classes from the round-robin list")
Fixes: dcc68b4d80 ("net: sch_ets: Add a new Qdisc")
Reported-by: Li Shuang <shuali@redhat.com>
Closes: https://issues.redhat.com/browse/RHEL-108026
Reviewed-by: Petr Machata <petrm@nvidia.com>
Co-developed-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Link: https://patch.msgid.link/7928ff6d17db47a2ae7cc205c44777b1f1950545.1755016081.git.dcaratti@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2025-08-13 18:11:48 -07:00
..
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
act_api.c
act_bpf.c
act_connmark.c
act_csum.c
act_ct.c
act_ctinfo.c
act_gact.c
act_gate.c
act_ife.c
act_meta_mark.c
act_meta_skbprio.c
act_meta_skbtcindex.c
act_mirred.c
act_mpls.c net_sched: act_mpls: use RCU in tcf_mpls_dump() 2025-07-11 16:01:16 -07:00
act_nat.c net_sched: act_nat: use RCU in tcf_nat_dump() 2025-07-11 16:01:16 -07:00
act_pedit.c net_sched: act_pedit: use RCU in tcf_pedit_dump() 2025-07-11 16:01:17 -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
act_simple.c
act_skbedit.c net_sched: act_skbedit: use RCU in tcf_skbedit_dump() 2025-07-11 16:01:17 -07:00
act_skbmod.c
act_tunnel_key.c
act_vlan.c
bpf_qdisc.c bpf: Clean up individual BTF_ID code 2025-07-16 18:34:42 -07:00
cls_api.c
cls_basic.c
cls_bpf.c
cls_cgroup.c
cls_flow.c
cls_flower.c
cls_fw.c
cls_matchall.c
cls_route.c
cls_u32.c
em_canid.c
em_cmp.c
em_ipset.c
em_ipt.c
em_meta.c
em_nbyte.c
em_text.c
em_u32.c
ematch.c
sch_api.c
sch_blackhole.c
sch_cake.c
sch_cbs.c
sch_choke.c
sch_codel.c
sch_drr.c
sch_dualpi2.c sched: Add enqueue/dequeue of dualpi2 qdisc 2025-07-23 17:52:07 -07:00
sch_etf.c
sch_ets.c net/sched: ets: use old 'nbands' while purging unused classes 2025-08-13 18:11:48 -07:00
sch_fifo.c
sch_fq.c
sch_fq_codel.c
sch_fq_pie.c
sch_frag.c
sch_generic.c net/sched: Add precise drop reason for pfifo_fast queue overflows 2025-07-25 15:47:21 -07:00
sch_gred.c
sch_hfsc.c
sch_hhf.c
sch_htb.c net/sched: Return NULL when htb_lookup_leaf encounters an empty rbtree 2025-07-17 07:47:55 -07:00
sch_ingress.c
sch_mq.c
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
sch_mqprio_lib.h
sch_multiq.c
sch_netem.c
sch_pie.c
sch_plug.c
sch_prio.c
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
sch_sfb.c
sch_sfq.c
sch_skbprio.c
sch_taprio.c net/sched: taprio: enforce minimum value for picos_per_byte 2025-08-01 15:15:28 -07:00
sch_tbf.c
sch_teql.c