FreeBSD: VID-ab437561-47c0-11ee-8e38-002590c1f29c (CVE-2023-3494): FreeBSD -- bhyve privileged guest escape via fwctl

Problem Description: The fwctl driver implements a state machine which is executed when the guest accesses certain x86 I/O ports. The interface lets the guest copy a string into a buffer resident in the bhyve process' memory. A bug in the state machine implementation can result in a buffer overflowing when copying this string. Impact: A malicious, privileged software running in a guest VM can exploit the buffer overflow to achieve code execution on the host in the bhyve userspace process, which typically runs as root. Note that bhyve runs in a Capsicum sandbox, so malicious code is constrained by the capabilities available to the bhyve process.