The alloc_domain_struct function in arch/arm/domain.c in Xen 4.4.x, when running on an ARM platform, does not properly initialize the structure containing the grant table pages for a domain, which allows local guest administrators to obtain sensitive information via the GNTTABOP_setup_table subhypercall.
http://xenbits.xen.org/xsa/advisory-101.html
http://www.securitytracker.com/id/1030471