CVE-2025-21827

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

Bluetooth: btusb: mediatek: Add locks for usb_driver_claim_interface()

The documentation for usb_driver_claim_interface() says that "the device lock" is needed when the function is called from places other than probe(). This appears to be the lock for the USB interface device. The Mediatek btusb code gets called via this path:

Workqueue: hci0 hci_power_on [bluetooth] Call trace: usb_driver_claim_interface btusb_mtk_claim_iso_intf btusb_mtk_setup hci_dev_open_sync hci_power_on process_scheduled_works worker_thread kthread

With the above call trace the device lock hasn't been claimed. Claim it.

Without this fix, we'd sometimes see the error "Failed to claim iso interface". Sometimes we'd even see worse errors, like a NULL pointer dereference (where intf->dev.driver was NULL) with a trace like:

Call trace: usb_suspend_both usb_runtime_suspend __rpm_callback rpm_suspend pm_runtime_work process_scheduled_works

Both errors appear to be fixed with the proper locking.