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.
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
| Link | Tags |
|---|---|
| https://xenbits.xenproject.org/xsa/advisory-401.txt | vendor advisory |
| http://xenbits.xen.org/xsa/advisory-401.html | patch vendor advisory |
| http://www.openwall.com/lists/oss-security/2022/06/09/3 | third party advisory mailing list |
| https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OH65U6FTTB5MLH5A6Q3TW7KVCGOG4MYI/ | vendor advisory |
| http://packetstormsecurity.com/files/167718/Xen-TLB-Flush-Bypass.html | third party advisory vdb entry |
| https://www.debian.org/security/2022/dsa-5184 | third party advisory vendor advisory |
| https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RKRXZ4LHGCGMOG24ZCEJNY6R2BTS4S2Q/ | vendor advisory |
| https://security.gentoo.org/glsa/202208-23 | third party advisory vendor advisory |