kernel: Bluetooth: hci_core: Fix use-after-free in vhci_flush()

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hcicore: Fix use-after-free in vhciflush syzbot reported use-after-free in vhciflush without repro. 0 From the splat, a thread closed a vhci file descriptor while its device was being used by iotcl on another thread...