CVE ID:	CVE-2020-25601
Description:	An issue was discovered in Xen through 4.14.x. There is a lack of preemption in evtchn_reset() / evtchn_destroy(). In particular, the FIFO event channel model allows guests to have a large number of event channels active at a time. Closing all of these (when resetting all event channels or when cleaning up after the guest) may take extended periods of time. So far, there was no arrangement for preemption at suitable intervals, allowing a CPU to spend an almost unbounded amount of time in the processing of these operations. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system. All Xen versions are vulnerable in principle. Whether versions 4.3 and older are vulnerable depends on underlying hardware characteristics.
Test IDs:	None available
Cross References:	Common Vulnerability Exposure (CVE) ID: CVE-2020-25601 Debian Security Information: DSA-4769 (Google Search) https://www.debian.org/security/2020/dsa-4769 https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4JRXMKEMQRQYWYEPHVBIWUEAVQ3LU4FN/ https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RJZERRBJN6E6STDCHT4JHP4MI6TKBCJE/ https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DA633Y3G5KX7MKRN4PFEGM3IVTJMBEOM/ https://security.gentoo.org/glsa/202011-06 https://xenbits.xen.org/xsa/advisory-344.html SuSE Security Announcement: openSUSE-SU-2020:1608 (Google Search) http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00008.html