The xen_biovec_phys_mergeable function in drivers/xen/biomerge.c in Xen might allow local OS guest users to corrupt block device data streams and consequently obtain sensitive memory information, cause a denial of service, or gain host OS privileges by leveraging incorrect block IO merge-ability calculation.
www.debian.org/security/2017/dsa-3981
www.openwall.com/lists/oss-security/2017/08/15/4
www.securityfocus.com/bid/100343
www.securitytracker.com/id/1039176
xenbits.xen.org/xsa/advisory-229.html
bugzilla.redhat.com/show_bug.cgi?id=1477656
security.gentoo.org/glsa/201801-14
support.citrix.com/article/CTX225941
usn.ubuntu.com/3655-1/
usn.ubuntu.com/3655-2/