CVE-2026-43421usb: gadget: f_ncm: Fix net_device lifecycle with device_move

Official description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_ncm: Fix net_device lifecycle with device_move The network device outlived its parent gadget device during disconnection, resulting in dangling sysfs links and null pointer dereference problems. A prior attempt to solve this by removing SET_NETDEV_DEV entirely [1] was reverted due to power management ordering concerns and a NO-CARRIER regression. A subsequent attempt to defer net_device allocation to bind [2] broke 1:1 mapping between function instance and network device, making it impossible for configfs to report the resolved interface name. This results in a regression where the DHCP server fails on pmOS. Use device_move to reparent the net_device between the gadget device and /sys/devices/virtual/ across bind/unbind cycles. This preserves the network interface across USB reconnection, allowing the DHCP server to retain their binding. Introduce gether_attach_gadget()/gether_detach_gadget() helpers and use __free(detach_gadget) macro to undo attachment on bind failure. The bind_count ensures device_move executes only on the first bind. [1] https://lore.kernel.org/lkml/f2a4f9847617a0929d62025748384092e5f35cce.camel@crapouillou.net/ [2] https://lore.kernel.org/linux-usb/795ea759-7eaf-4f78-81f4-01ffbf2d7961@ixit.cz/

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/7c97366f5dac5255e60a317ffe3a5b18f3745547
• https://git.kernel.org/stable/c/36c41e9724c9a7a7cda37f5a4e9d94f25c8031c4
• https://git.kernel.org/stable/c/93f116c3393a22acab96ad1bef12b2572eb80ca4
• https://git.kernel.org/stable/c/e584cb58a2ea7ff4d3a4bc43d5ca512ed3ecb77d
• https://git.kernel.org/stable/c/85acaba2f42b557499bab3608307f17bf13beb69
• https://git.kernel.org/stable/c/ec35c1969650e7cb6c8a91020e568ed46e3551b0
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html