CVE ID:	CVE-2020-29569
Description:	An issue was discovered in the Linux kernel through 5.10.1, as used with Xen through 4.14.x. The Linux kernel PV block backend expects the kernel thread handler to reset ring->xenblkd to NULL when stopped. However, the handler may not have time to run if the frontend quickly toggles between the states connect and disconnect. As a consequence, the block backend may re-use a pointer after it was freed. A misbehaving guest can trigger a dom0 crash by continuously connecting / disconnecting a block frontend. Privilege escalation and information leaks cannot be ruled out. This only affects systems with a Linux blkback.
Test IDs:	1.3.6.1.4.1.25623.1.0.892557   1.3.6.1.4.1.25623.1.0.892586   1.3.6.1.4.1.25623.1.0.704843
Cross References:	Common Vulnerability Exposure (CVE) ID: CVE-2020-29569 Debian Security Information: DSA-4843 (Google Search) https://www.debian.org/security/2021/dsa-4843 https://security.gentoo.org/glsa/202107-30 https://xenbits.xenproject.org/xsa/advisory-350.html https://lists.debian.org/debian-lts-announce/2021/02/msg00018.html https://lists.debian.org/debian-lts-announce/2021/03/msg00010.html