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Thu, 6 Aug 2026 01:08:22 -0700 From: Dragos Tatulea To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jacob Keller , Stanislav Fomichev CC: Dragos Tatulea , , Shahar Shitrit , , Subject: [PATCH net v2] net: Defer netdev KOBJ_ADD uevent until the device is published Date: Thu, 6 Aug 2026 11:07:58 +0300 Message-ID: <20260806080758.2039586-2-dtatulea@nvidia.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH1PEPF0000AD7C:EE_|SJ5PPF4C71815F9:EE_ X-MS-Office365-Filtering-Correlation-Id: 83e2c69e-dec4-4fcf-659c-08def391ea7d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|23010399003|36860700016|82310400026|1800799024|13003099007|6133799003|10067099003|11063799006|56012099006|18002099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.118.233;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge2.nvidia.com;CAT:NONE;SFS:(13230040)(376014)(23010399003)(36860700016)(82310400026)(1800799024)(13003099007)(6133799003)(10067099003)(11063799006)(56012099006)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: yqn1h1v4MiarwrqZoMhpANWkkVt+8UItBPOplt5nft4Kwqz6RKFg0uiTpgsiVy156l76ZMO1On/4g0ECCl+MRj3m0MuD68W8eqWouKIadoFVp9pjkfVAOVBwUTRjneygSWv9sWweFYcCXjgZdxpBYwc8aqU3wMiWOqGGLBAK6qzUjpeeT81eqdgGcvd35+bhqWXuIPzQZlaIs8UG5MsifVaz+rN+YDIKYsFzclj7Pgmrc4ip4eo1m2WOrzjYhp6cpO6+qRsCuGK2sO014S4bohM9QbFqm3e8cQYoy07GfTgz2yk3xmFJl8epwC+ptq3igXjKjmZPcDqYNQL1wrFYfmV4Kr4kVrW13hHomgpzF0zYF7n14UYjbgRitVF/Nd9Nw8cAOVCTPHQWgoBkBs778B62tQ9nLhwd6GxmDjYTFokC85RNLsbf8nAOGlc5G42B X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Aug 2026 08:08:36.1712 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 83e2c69e-dec4-4fcf-659c-08def391ea7d X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.233];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CH1PEPF0000AD7C.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ5PPF4C71815F9 netdev_register_kobject() calls device_add(), which emits KOBJ_ADD and wakes udev, but register_netdevice() only makes the device findable by name later, in list_netdevice(). A udev worker that reacts to the uevent can therefore run against a device that no lookup can find yet. This used to be harmless because the ethtool ioctl took the rtnl_lock when looking the device up, and register_netdevice() runs under rtnl, so the worker simply blocked until registration finished. The commit in the fixes tag moved the lookup out from under rtnl for ops-locked drivers. Now there is a short window in register_netdevice() between netdev_register_kobject() until list_netdevice() when the device is not findable by name. This was reproduced with the mlx5 driver on a kernel with KASAN enabled during devlink reload: systemd-udevd's net_driver builtin gets -ENODEV from ETHTOOL_GDRVINFO, which was preventing interface renaming. Suppress the uevent in netdev_register_kobject() and emit it from register_netdevice() next to rtmsg_ifinfo(). This is the last point in register_netdevice() where no error can happen, so only fully registered devices are announced: the registration error paths never reach it, and the device_del() that unwinds them stays silent as well, leaving userspace with neither an add nor a remove. Fixes: f994752b1127 ("net: ethtool: optionally skip rtnl_lock on IOCTL path") Assisted-by: Claude:claude-opus-5 Signed-off-by: Dragos Tatulea Reviewed-by: Shahar Shitrit --- Changes in v2: - Addressed Jakub's comments on code comments. - Link to v1: https://lore.kernel.org/all/20260804155103.742898-1-dtatulea@nvidia.com/ --- net/core/dev.c | 1 + net/core/net-sysfs.c | 14 ++++++++++++++ net/core/net-sysfs.h | 1 + 3 files changed, 16 insertions(+) diff --git a/net/core/dev.c b/net/core/dev.c index c1c1be1a6962..32cc092d5d11 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -11499,6 +11499,7 @@ int register_netdevice(struct net_device *dev) * Prevent userspace races by waiting until the network * device is fully setup before sending notifications. */ + netdev_uevent_add(dev); if (!(dev->rtnl_link_ops && dev->rtnl_link_initializing)) rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U, GFP_KERNEL, 0, NULL); diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c index 0e71c9ed41e8..25546deacec8 100644 --- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -2334,6 +2334,9 @@ int netdev_register_kobject(struct net_device *ndev) *groups++ = &wireless_group; #endif /* CONFIG_SYSFS */ + /* Hold back the KOBJ_ADD uevent until the device is listed. */ + dev_set_uevent_suppress(dev, 1); + error = device_add(dev); if (error) return error; @@ -2349,6 +2352,17 @@ int netdev_register_kobject(struct net_device *ndev) return error; } +/* Announce a fully registered device to userspace. This pairs with the uevent + * suppression from netdev_register_kobject(). + */ +void netdev_uevent_add(struct net_device *ndev) +{ + struct device *dev = &ndev->dev; + + dev_set_uevent_suppress(dev, 0); + kobject_uevent(&dev->kobj, KOBJ_ADD); +} + /* Change owner for sysfs entries when moving network devices across network * namespaces owned by different user namespaces. */ diff --git a/net/core/net-sysfs.h b/net/core/net-sysfs.h index 38e2e3ffd0bd..2f41a4dee866 100644 --- a/net/core/net-sysfs.h +++ b/net/core/net-sysfs.h @@ -4,6 +4,7 @@ int __init netdev_kobject_init(void); int netdev_register_kobject(struct net_device *); +void netdev_uevent_add(struct net_device *dev); void netdev_unregister_kobject(struct net_device *); int net_rx_queue_update_kobjects(struct net_device *, int old_num, int new_num); int netdev_queue_update_kobjects(struct net_device *net, -- 2.55.0