CVE-2023-46835

Name	CVE-2023-46835
Description	The current setup of the quarantine page tables assumes that the quarantine domain (dom_io) has been initialized with an address width of DEFAULT_DOMAIN_ADDRESS_WIDTH (48) and hence 4 page table levels. However dom_io being a PV domain gets the AMD-Vi IOMMU page tables levels based on the maximum (hot pluggable) RAM address, and hence on systems with no RAM above the 512GB mark only 3 page-table levels are configured in the IOMMU. On systems without RAM above the 512GB boundary amd_iommu_quarantine_init() will setup page tables for the scratch page with 4 levels, while the IOMMU will be configured to use 3 levels only, resulting in the last page table directory (PDE) effectively becoming a page table entry (PTE), and hence a device in quarantine mode gaining write access to the page destined to be a PDE. Due to this page table level mismatch, the sink page the device gets read/write access to is no longer cleared between device assignment, possibly leading to data leaks.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1056928

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
xen (PTS)	bullseye	4.14.6-1	vulnerable
	bullseye (security)	4.14.5+94-ge49571868d-1	vulnerable
	bookworm	4.17.3+10-g091466ba55-1~deb12u1	fixed
	sid, trixie	4.17.3+36-g54dacb5c02-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Debian Bugs
xen	source	buster	(unfixed)	end-of-life
xen	source	bullseye	(unfixed)	end-of-life
xen	source	bookworm	4.17.2+76-ge1f9cb16e2-1~deb12u1
xen	source	(unstable)	4.17.2+76-ge1f9cb16e2-1		1056928

[bullseye] - xen <end-of-life> (EOLed in Bullseye)
[buster] - xen <end-of-life> (DSA 4677-1)
https://xenbits.xen.org/xsa/advisory-445.html