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

Bluetooth: hci_conn: fix potential UAF in set_cig_params_sync

hci_conn lookup and field access must be covered by hdev lock in
set_cig_params_sync, otherwise it's possible it is freed concurrently.

Take hdev lock to prevent hci_conn from being deleted or modified
concurrently. Just RCU lock is not suitable here, as we also want to
avoid "tearing" in the configuration.