x86 pv: Race condition in typeref acquisition Xen maintains a type reference count for pages, in addition to a regular reference count. This scheme is used to maintain invariants required for Xen's safety, e.g. PV guests may not have direct writeable access to pagetables; updates need auditing by Xen. Unfortunately, the logic for acquiring a type reference has a race condition, whereby a safely TLB flush is issued too early and creates a window where the guest can re-establish the read/write mapping before writeability is prohibited.
http://www.openwall.com/lists/oss-security/2022/06/09/3
https://xenbits.xenproject.org/xsa/advisory-401.txt
http://xenbits.xen.org/xsa/advisory-401.html
http://packetstormsecurity.com/files/167718/Xen-TLB-Flush-Bypass.html
Source: MITRE
Published: 2022-06-09
Updated: 2022-08-24
Type: CWE-362
Base Score: 6.9
Vector: AV:L/AC:M/Au:N/C:C/I:C/A:C
Impact Score: 10
Exploitability Score: 3.4
Severity: MEDIUM
Base Score: 6.4
Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 0.5
Severity: MEDIUM