Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: f_ecm: Fix net_device lifecycle with device_move
The net_device is allocated during function instance creation and registered during the bind phase with the gadget device as its sysfs parent. When the function unbinds, the parent device is destroyed, but the net_device survives, resulting in dangling sysfs symlinks:
console:/ # ls -l /sys/class/net/usb0 lrwxrwxrwx … /sys/class/net/usb0 -> /sys/devices/platform/…/gadget.0/net/usb0 console:/ # ls -l /sys/devices/platform/…/gadget.0/net/usb0 ls: …/gadget.0/net/usb0: No such file or directory
Use device_move() to reparent the net_device between the gadget device tree and /sys/devices/virtual across bind and unbind cycles. During the final unbind, calling device_move(NULL) moves the net_device to the virtual device tree before the gadget device is destroyed. On rebinding, device_move() reparents the device back under the new gadget, ensuring proper sysfs topology and power management ordering.
To maintain compatibility with legacy composite drivers (e.g., multi.c), the bound flag is used to indicate whether the network device is shared and pre-registered during the legacy driver’s bind phase.
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , Oracle Linux 7 ELS , TuxCare 9.6 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
- Affected packages:
- kernel @ 4.18.0 (+9 more)
In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: f_ecm: Fix net_device lifecycle with device_move
The net_device is allocated during function instance creation and registered during the bind phase with the gadget device as its sysfs parent. When the function unbinds, the parent device is destroyed, but the net_device survives, resulting in dangling sysfs symlinks:
console:/ # ls -l /sys/class/net/usb0 lrwxrwxrwx … /sys/class/net/usb0 -> /sys/devices/platform/…/gadget.0/net/usb0 console:/ # ls -l /sys/devices/platform/…/gadget.0/net/usb0 ls: …/gadget.0/net/usb0: No such file or directory
Use device_move() to reparent the net_device between the gadget device tree and /sys/devices/virtual across bind and unbind cycles. During the final unbind, calling device_move(NULL) moves the net_device to the virtual device tree before the gadget device is destroyed. On rebinding, device_move() reparents the device back under the new gadget, ensuring proper sysfs topology and power management ordering.
To maintain compatibility with legacy composite drivers (e.g., multi.c), the bound flag is used to indicate whether the network device is shared and pre-registered during the legacy driver’s bind phase.