In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_sync: annotate data-races around hdev->req_status
__hci_cmd_sync_sk() sets hdev->req_status under hdev->req_lock:
hdev->req_status = HCI_REQ_PEND;
However, several other functions read or write hdev->req_status without holding any lock:
- hci_send_cmd_sync() reads req_status in hci_cmd_work (workqueue)
- hci_cmd_sync_complete() reads/writes from HCI event completion
- hci_cmd_sync_cancel() / hci_cmd_sync_cancel_sync() read/write
- hci_abort_conn() reads in connection abort path
Since __hci_cmd_sync_sk() runs on hdev->req_workqueue while hci_send_cmd_sync() runs on hdev->workqueue, these are different workqueues that can execute concurrently on different CPUs. The plain C accesses constitute a data race.
Add READ_ONCE()/WRITE_ONCE() annotations on all concurrent accesses to hdev->req_status to prevent potential compiler optimizations that could affect correctness (e.g., load fusing in the wait_event condition or store reordering).