GameOver(lay) Privilege Escalation and Container Escape

This module exploits the use of unsafe functions in a number of Ubuntu kernels
utilizing vulnerable versions of overlayfs. To mitigate CVE-2021-3493 the Linux
kernel added a call to vfs_setxattr during ovl_do_setxattr. Due to independent
changes to the kernel by the Ubuntu development team __vfs_setxattr_noperm is
called during ovl_do_setxattr without calling the intermediate safety function
vfs_setxattr. Ultimatly this module allows for root access to be achieved by
writing setuid capabilities to a file which are not sanitized after being unioned
with the upper mounted directory.