In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hciconn: fix potential UAF in setcigparamssync hciconn lookup and field access must be covered by hdev lock in setcigparamssync, 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.