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emacs 30.1 From: Petr Machata To: Davide Caratti CC: Jamal Hadi Salim , Cong Wang , Jiri Pirko , "David S. Miller" , "Eric Dumazet" , Jakub Kicinski , "Paolo Abeni" , Simon Horman , Lion Ackermann , Petr Machata , , Ivan Vecera , Li Shuang Subject: Re: [PATCH net] net/sched: ets: use old 'nbands' while purging unused classes Date: Fri, 8 Aug 2025 13:44:59 +0200 In-Reply-To: Message-ID: <87ms8a9fuv.fsf@nvidia.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ5PEPF00000208:EE_|CH3PR12MB8880:EE_ X-MS-Office365-Filtering-Correlation-Id: e96e088a-332f-408d-3388-08ddd6745027 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|1800799024|82310400026|376014|7416014|13003099007; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?9k4L+Xrki+s6Btn7S2PMTq5ot3lUOEOVRowFdqpbw7gnvYumrcjpoiHUpEcb?= =?us-ascii?Q?3VwqGCxJcYNtcqBnUjoayY0OUVUy9fp/Er0nxn0juQIiRpTF+iKMtB+oco69?= =?us-ascii?Q?WafHE80bNlcUqGQQNXwuG1pq9c21fP9/qZUOgiAmP3qpRFu/A+cipOQGtFp/?= =?us-ascii?Q?oi6/aKjItIEzRiukFZDl1CheFVUp1gwb7pXLxbSbYSOYE+ZBX4WPF12cfSaW?= =?us-ascii?Q?X5I4IF7tlwWZPy7tEzsW/zlXB/bhZHL2aMdcF1MT4YVVISERiieqxM5gFidc?= =?us-ascii?Q?3UxMP5irAwpzpP/Aq6eUlTnVNO7+5PQmB/wT/0mtL2o9j1kgcVdeIWBp9Oo+?= =?us-ascii?Q?JGxiY6dxtRUcdZW5blUJo/W1689EHm04deRCUYUbrL0tP9QzI1pwmx6HXYKq?= =?us-ascii?Q?GSq3zQKSjcNJtECqHNhtp9uVnEQI2fYwIZC8AD5rZRYQ5mMgeyE990Tvu20K?= =?us-ascii?Q?IGf6qAmzYLL2RSHYaRfFrqPaXGljgJtjLlJW410W3Vfpm+O9gx12v8IJ4+E2?= =?us-ascii?Q?ErOitvNHel3mwpGok97ich418eSmkq7Q/+/5c/0+N93YI2btrFW2nM95V/lZ?= =?us-ascii?Q?dumNDxjMWcW2ZfR2CcP+hWDpjhgkZgIm3SARU/bh2/slClXy2r+gNJvkReEK?= =?us-ascii?Q?0rTZKx5zI6ZuAxcov7XpsoyGU0Z3tiCZh5tqkdwrKIK0qkWpy+V84Vnztd8r?= =?us-ascii?Q?2fn60gL/a3qMlxBt1r5vk0J5nLBvncpk2uBE9BsxEo5hTY33NSvGZWkGIYlN?= =?us-ascii?Q?OE+9z1F+u6DU9ZY2NsXAKdaxid8LV6F8n2Mr7+jB+u59Agqnho3/8FynOT9E?= =?us-ascii?Q?nLtpmcs2JqQenkesoUPRdzp5Xa/5SoYemIVIFY7h5IzodaRm7ywD5yXbLX9J?= =?us-ascii?Q?DZv+NZYHvHDdgYX7R4P/EUcgoFyw3PMy97AZzG4kB12grC3pYGpriYFaYLlf?= =?us-ascii?Q?cNVTnmo+azdN1V95JlbQtZ/Xe5+0zQ1xzXoO+dL1TxAeDDDt5g4/RqBwqrH7?= =?us-ascii?Q?Ybi9BcDJQ95aFXHXmEsh+hQTcTe/ZC6NYwWTiUuCZDrK2GC3m0WWmthsi8gH?= =?us-ascii?Q?7uSDvpgeSQJ/pdNNGeXobL+LW7sT1VlR5KnFISbkDEVJqyqZT2G87O9rRajN?= =?us-ascii?Q?phSzBp+8Rpy/PyTbYHr68XaHW2qq4tSG40F6I6DnMq3uarV7KEtqEyfk/6yI?= =?us-ascii?Q?1CSRQBOuHhiiEWcC8+VJeaxQ+nnERy/ld9XiT3VZAkPuPOC9P8rECiKYsY7d?= =?us-ascii?Q?PKTPOe++ZMQHHI3IesOSCjnwtsSWuvk9hiFLZc2QsENWEPbdWdvVba+9dcGK?= =?us-ascii?Q?5mEMmyFFrqj3tdkWNwacHI6AgIUS9ykXkxMfkoHTEgozj65FZOo/XGruRPaz?= =?us-ascii?Q?QHMHh7BDPGaTYR5GnjDvKoeFdpeuLD+mARKN1vQtK+3RO1tkhurCiikzwwQh?= =?us-ascii?Q?Y884F5UEkOU7PGPXfsmz5Hfw7oP9F7h3VSHq/HSjIod4cCP/NeGxH+oDyUh9?= =?us-ascii?Q?E/lfTkQWYoM723BHytZxMD4yWJJO8t6ww/GweR/Z1yKm5gx3CoUewqR0ZQ?= =?us-ascii?Q?=3D=3D?= X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230040)(36860700013)(1800799024)(82310400026)(376014)(7416014)(13003099007);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Aug 2025 12:08:40.5481 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: e96e088a-332f-408d-3388-08ddd6745027 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SJ5PEPF00000208.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB8880 Davide Caratti writes: > 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: First let me just note: that is one sharp paragraph edge! > - old 'q->nbands' because it's needed by ets_class_find() Comes from qdisc_purge_queue() calls qdisc_tree_reduce_backlog() calls Qdisc_class_ops.find, which is ets_class_find(). > - old 'q->nstrict' because it's needed by ets_class_is_strict() >From qdisc_purge_queue() calls qdisc_tree_reduce_backlog() calls Qdisc_class_ops.qlen_notify, which is ets_class_qlen_notify() calls ets_class_is_strict(). Also qdisc_purge_queue() calls qdisc_reset() calls Qdisc_ops.reset which is ets_qdisc_reset(), and that accesses both fields. > 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: > > 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 > > > [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/ > > Fixes: 103406b38c60 ("net/sched: Always pass notifications when child class becomes empty") > Fixes: c062f2a0b04d ("net/sched: sch_ets: don't remove idle classes from the round-robin list") > Fixes: dcc68b4d8084 ("net: sch_ets: Add a new Qdisc") > Reported-by: Li Shuang > Closes: https://issues.redhat.com/browse/RHEL-108026 > Co-developed-by: Ivan Vecera > Signed-off-by: Ivan Vecera > Signed-off-by: Davide Caratti Reviewed-by: Petr Machata > --- > net/sched/sch_ets.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/net/sched/sch_ets.c b/net/sched/sch_ets.c > index 037f764822b9..82635dd2cfa5 100644 > --- a/net/sched/sch_ets.c > +++ b/net/sched/sch_ets.c > @@ -651,6 +651,12 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt, > > sch_tree_lock(sch); > > + for (i = nbands; i < oldbands; i++) { > + if (i >= q->nstrict && q->classes[i].qdisc->q.qlen) > + list_del_init(&q->classes[i].alist); > + qdisc_purge_queue(q->classes[i].qdisc); > + } > + > WRITE_ONCE(q->nbands, nbands); > for (i = nstrict; i < q->nstrict; i++) { > if (q->classes[i].qdisc->q.qlen) { > @@ -658,11 +664,6 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt, > q->classes[i].deficit = quanta[i]; > } > } > - for (i = q->nbands; i < oldbands; i++) { > - if (i >= q->nstrict && q->classes[i].qdisc->q.qlen) > - list_del_init(&q->classes[i].alist); > - qdisc_purge_queue(q->classes[i].qdisc); > - } > WRITE_ONCE(q->nstrict, nstrict); > memcpy(q->prio2band, priomap, sizeof(priomap));