An attacker in a domU could perform a denial of service attack on Xen by accessing a memory region shared with the hypervisor, while Xen is performing an atomic operation on the same region. As a result Xen could end up looping boundlessly. Systems running all versions of Xen are affected. x86 processors are not affected. Arm processors are vulnerable, both Armv7 and Armv8.
Created xen tracking bugs for this issue:
Affects: fedora-all [bug 1720760]