Multiple issues in ctl(4) CAM Target Layer

The function ctl_write_buffer incorrectly set a flag which resulted in a kernel Use-After-Free when a command finished processing. Malicious software running in a guest VM that exposes virtio_scsi can exploit the vulnerabilities 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. A malicious iSCSI initiator could achieve remote code execution on the iSCSI target host.