An issue was discovered in drivers/xen/balloon.c in the Linux kernel before 5.2.3, as used in Xen through 4.12.x, allowing guest OS users to cause a denial of service because of unrestricted resource consumption during the mapping of guest memory, aka CID-6ef36ab967c7.
https://xenbits.xen.org/xsa/advisory-300.html
https://usn.ubuntu.com/4286-2/
https://usn.ubuntu.com/4286-1/
https://security.netapp.com/advisory/ntap-20191031-0005/
https://github.com/torvalds/linux/commit/6ef36ab967c71690ebe7e5ef997a8be4da3bc844
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.2.3