CVE-2026-64233

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

usb: gadget: uvc: hold opts->lock across XU walks in uvc_function_bind

uvc_function_bind() walks &opts->extension_units twice without holding

opts->lock:

- directly, for the iExtension string-descriptor fixup loop;

- indirectly, four times via uvc_copy_descriptors() (once per speed),

where the helper iterates uvc->desc.extension_units (which aliases

&opts->extension_units) to size and emit XU descriptors.

The configfs side (uvcg_extension_make / uvcg_extension_drop, in

drivers/usb/gadget/function/uvc_configfs.c) takes opts->lock around its

list_add_tail / list_del operations. A privileged userspace process

that holds the configfs subtree open and writes the gadget UDC name

to bind the function while concurrently rmdir()'ing an extensions

subdir can race uvcg_extension_drop() against the bind-time list walks

and dereference a freed struct uvcg_extension.

Hold opts->lock from the start of the XU string-descriptor fixup

through the last uvc_copy_descriptors() call, releasing on the

descriptor-error path via a new error_unlock label that drops the

lock before falling through to the existing error label. This

matches the locking discipline of the configfs callbacks and removes

the only remaining unsynchronised reader of the XU list during bind.

Reachability: only privileged processes that can mount configfs and

write to gadget UDC files can trigger the race, so this is a

correctness fix rather than a security boundary.