CVE-2026-31721

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: f_hid: move list and spinlock inits from bind to alloc

There was an issue when you did the following:

- setup and bind an hid gadget

- open /dev/hidg0

- use the resulting fd in EPOLL_CTL_ADD

- unbind the UDC

- bind the UDC

- use the fd in EPOLL_CTL_DEL

When CONFIG_DEBUG_LIST was enabled, a list_del corruption was reported

within remove_wait_queue (via ep_remove_wait_queue). After some

debugging I found out that the queues, which f_hid registers via

poll_wait were the problem. These were initialized using

init_waitqueue_head inside hidg_bind. So effectively, the bind function

re-initialized the queues while there were still items in them.

The solution is to move the initialization from hidg_bind to hidg_alloc

to extend their lifetimes to the lifetime of the function instance.

Additionally, I found many other possibly problematic init calls in the

bind function, which I moved as well.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References