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Tue, 4 Aug 2026 08:51:22 -0700 From: Dragos Tatulea To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Stanislav Fomichev , Jacob Keller CC: Dragos Tatulea , , , , Subject: [PATCH net] net: Defer netdev KOBJ_ADD uevent until the device is published Date: Tue, 4 Aug 2026 18:51:01 +0300 Message-ID: <20260804155103.742898-1-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: CH2PEPF00000143:EE_|CH3PR12MB8710:EE_ X-MS-Office365-Filtering-Correlation-Id: cc3bf16e-2118-434c-4a97-08def24049f0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|36860700016|23010399003|376014|1800799024|56012099006|10067099003|11063799006|6133799003|18002099003; X-Microsoft-Antispam-Message-Info: yFzlBdu9ZxU2Rz+zQUyI7tpVWqlLlJdLvY/JmcAWMK4m/XL+Du5rV2jt4xB/2c91T+Rd+XWaFkXBfRuMXIhmaBeRDZTatcBCbdeHDRTeteATCaiQMyqkfV0Epa6I8IRabKhyBD/7In4PG91tMZX1maMEgRagJXqeoB7mCBwMKme27stws/U5SorV8J82wHSCDnfjhVCIZG5LRbHmo5oslS7bgw4VGwm/Hne8zv89Ls+8B4WRqSW/8LBL1zD5rY8TN4JMfGZ2MhkUhQTCAuCHTpzZzcqVymzvGLlFliPkFtIVY201f+fNL1qQAi1x+/GO1sk26H9ANk+9qxxg0uNN8NyfZO3PxgXD4Y5IEqttJre2aC9agU8G3/7XYwUlkOHd0WOw49eVSQvCFJozGC5JHg2E1C3QZnZN7q54pFizhoyBGfcXJnTxkrLvrMqmO/3Pqn8rTmlT0iDurLdz8Pkwo+snJA8ou1HVwqTITJiSL46GmSR/cgNqR4q+DMrMe9sJI4Bn/H4uhvcyNetB4SK3HqNCQc0DcEoVpCwn+3C4Mvs7lLIYbo2uN+byPRxGOejB5Ma7gDxPPLuVNYwaqXLb875ZmmL7ReabhMKoRsDRPGrsgQDE9QKr2X75Yup8hPsDwwDnmZNsh5eSTKC9tw+QccQTA5Qlg8XnFnP+dHYNV2LnQHZElec/zbmnj0fTidwQ6sv/svqhOcrRnllNwbQChw== X-Forefront-Antispam-Report: CIP:216.228.118.232;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge1.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(36860700016)(23010399003)(376014)(1800799024)(56012099006)(10067099003)(11063799006)(6133799003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 3oO/u4JX6QQmeoEeonXucOipJpLdTjCOUjXX9pvpeQpq3yksGU0Ug/9zZqRoLYL1s1y0zFfX/+JqJOSxiHRoasXSzpp6V+lmd1khPDnQx3tU3JgTLNB77rxg+djnFGlwXdqWQnkL6uXt2NMTnVsTEqGI9chl0tTPBkgSLwOElszdYbOV/vZe8zpU33eLTbfSh2xhX2lsepYiBezfft9GFckvEq2SRt6qXfURyR7bXUUH5znp1jJjVbxSOa2Jpvk3QVbL8SdkkweDQRScB/2QLsee55vikYVL8WmAZ4Bskm6KED2ROpXpABCZdrdAtgt16J4kqqN3qcVt9k7fDTuamkaUhwALplPp8+qg4UN6JWOuv5Ifiu9X7escvhL/PJeOFJzMiTNZN6fAZWJeLEzKcJ7kG9UX3xkb5UQ9KeIaqpamyxEV/nexlf6uwmXqMNkP X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Aug 2026 15:51:46.4258 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: cc3bf16e-2118-434c-4a97-08def24049f0 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CH2PEPF00000143.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB8710 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 --- net/core/dev.c | 1 + net/core/net-sysfs.c | 16 ++++++++++++++++ net/core/net-sysfs.h | 1 + 3 files changed, 18 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..9a403259a3d0 100644 --- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -2334,6 +2334,11 @@ int netdev_register_kobject(struct net_device *ndev) *groups++ = &wireless_group; #endif /* CONFIG_SYSFS */ + /* Hold back the KOBJ_ADD uevent until the device is discoverable + * by name. + */ + dev_set_uevent_suppress(dev, 1); + error = device_add(dev); if (error) return error; @@ -2349,6 +2354,17 @@ 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