Out-of-Bounds Affecting xen package, versions <4.9.0-r7

Note: Versions mentioned in the description apply only to the upstream xen package and not the xen package as distributed by Alpine. See How to fix? for Alpine:3.20 relevant fixed versions and status.

An issue was discovered in Xen through 4.9.x. Grant copying code made an implication that any grant pin would be accompanied by a suitable page reference. Other portions of code, however, did not match up with that assumption. When such a grant copy operation is being done on a grant of a dying domain, the assumption turns out wrong. A malicious guest administrator can cause hypervisor memory corruption, most likely resulting in host crash and a Denial of Service. Privilege escalation and information leaks cannot be ruled out.

• http://www.securityfocus.com/bid/101564
• https://support.citrix.com/article/CTX229057
• http://xenbits.xen.org/xsa/advisory-236.html
• https://www.debian.org/security/2017/dsa-4050
• https://lists.debian.org/debian-lts-announce/2018/10/msg00009.html
• http://www.openwall.com/lists/oss-security/2017/10/24/3
• http://www.securitytracker.com/id/1039653