Sandbox Escape: Linux 3.4+: arbitrary write with CONFIG_X86_X32

asmlinkage long compatsysrecvmmsgint fd, struct compatmmsghdr user mmsg, unsigned int vlen, unsigned int flags, struct compattimespec user timeout int datagrams; struct timespec ktspec; if flags & MSGCMSGCOMPAT return -EINVAL; if COMPATUSE64BITTIME return sysrecvmmsgfd, struct mmsghdr user mmsg,...