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