FreeBSD: VID-53b3474c-f680-11e9-a87f-a4badb2f4699 (CVE-2019-5603): FreeBSD -- Reference count overflow in mqueue filesystem 32-bit compat

Problem Description: System calls operating on file descriptors obtain a reference to relevant struct file which due to a programming error was not always put back, which in turn could be used to overflow the counter of affected struct file. Impact: A local user can use this flaw to obtain access to files, directories, sockets, etc., opened by processes owned by other users. If obtained struct file represents a directory from outside of user's jail, it can be used to access files outside of the jail. If the user in question is a jailed root they can obtain root privileges on the host system.