CVE-2026-31728usb: gadget: u_ether: Fix race between gether_disconnect and eth_stop

Official description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: u_ether: Fix race between gether_disconnect and eth_stop A race condition between gether_disconnect() and eth_stop() leads to a NULL pointer dereference. Specifically, if eth_stop() is triggered concurrently while gether_disconnect() is tearing down the endpoints, eth_stop() attempts to access the cleared endpoint descriptor, causing the following NPE: Unable to handle kernel NULL pointer dereference Call trace: __dwc3_gadget_ep_enable+0x60/0x788 dwc3_gadget_ep_enable+0x70/0xe4 usb_ep_enable+0x60/0x15c eth_stop+0xb8/0x108 Because eth_stop() crashes while holding the dev->lock, the thread running gether_disconnect() fails to acquire the same lock and spins forever, resulting in a hardlockup: Core - Debugging Information for Hardlockup core(7) Call trace: queued_spin_lock_slowpath+0x94/0x488 _raw_spin_lock+0x64/0x6c gether_disconnect+0x19c/0x1e8 ncm_set_alt+0x68/0x1a0 composite_setup+0x6a0/0xc50 The root cause is that the clearing of dev->port_usb in gether_disconnect() is delayed until the end of the function. Move the clearing of dev->port_usb to the very beginning of gether_disconnect() while holding dev->lock. This cuts off the link immediately, ensuring eth_stop() will see dev->port_usb as NULL and safely bail out.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/f02980594deef751e42133714aee25228f1494c6
• https://git.kernel.org/stable/c/e1e7a66584bf0aff3becb73c19fa31527889fc9e
• https://git.kernel.org/stable/c/a259ba0bce3b192c04334499690372a250f7d0b1
• https://git.kernel.org/stable/c/f6813c2b2ae78def76b69e0f9d72f80e4a1c4aca
• https://git.kernel.org/stable/c/bbb09bb89ffa571475f66daca9482b974cd29d6a
• https://git.kernel.org/stable/c/6ad77458637b78ec655e3da5f112c862e6690a9d
• https://git.kernel.org/stable/c/8ff689edfeceb5e3ec1623e09af2b2aa0f1098a8
• https://git.kernel.org/stable/c/e1eabb072c75681f78312c484ccfffb7430f206e