flatpak: TIOCLINUX can send commands outside sandbox if running on a virtual console

A flaw was found in Flatpak, a system for building, distributing, and running sandboxed desktop applications on Linux. It contains a vulnerability similar to CVE-2017-5226 but using the TIOCLINUX ioctl command instead of TIOCSTI. If a Flatpak app is run on a Linux virtual console such as /dev/tty...