# CVE-2023-46835: xen: The current setup of the quarantine page tables assumes that the quarantine domain (dom_io) has been initialized with...

CVE-2023-46835 is fixed in xen on 1 platform, first by DEBIAN-CVE-2023-46835, released January 5, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2023-46835
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0028
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jan 5, 2024

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | xen Debian 12.15 (bookworm) | 4.17.2+76-ge1f9cb16e2-1~deb12u1 | [DEBIAN-CVE-2023-46835](https://patchblox.com/security/data/fix/linux/debian-cve-2023-46835.md) | Jan 5, 2024 |
| Linux | xen Debian 13.5 (trixie) | 4.17.2+76-ge1f9cb16e2-1 | [DEBIAN-CVE-2023-46835](https://patchblox.com/security/data/fix/linux/debian-cve-2023-46835.md) | Jan 5, 2024 |
| Linux | xen Debian 14 | 4.17.2+76-ge1f9cb16e2-1 | [DEBIAN-CVE-2023-46835](https://patchblox.com/security/data/fix/linux/debian-cve-2023-46835.md) | Jan 5, 2024 |

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