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HIGH

iommu: disable SVA when CONFIG_X86 is set

Published Jan 13, 2026

Description

Patch series "Fix stale IOTLB entries for kernel address space", v7.

This proposes a fix for a security vulnerability related to IOMMU Shared Virtual Addressing (SVA). In an SVA context, an IOMMU can cache kernel page table entries. When a kernel page table page is freed and reallocated for another purpose, the IOMMU might still hold stale, incorrect entries. This can be exploited to cause a use-after-free or write-after-free condition, potentially leading to privilege escalation or data corruption.

This solution introduces a deferred freeing mechanism for kernel page table pages, which provides a safe window to notify the IOMMU to invalidate its caches before the page is reused.

This patch (of 8):

In the IOMMU Shared Virtual Addressing (SVA) context, the IOMMU hardware shares and walks the CPU's page tables. The x86 architecture maps the kernel's virtual address space into the upper portion of every process's page table. Consequently, in an SVA context, the IOMMU hardware can walk and cache kernel page table entries.

The Linux kernel currently lacks a notification mechanism for kernel page table changes, specifically when page table pages are freed and reused. The IOMMU driver is only notified of changes to user virtual address mappings. This can cause the IOMMU's internal caches to retain stale entries for kernel VA.

Use-After-Free (UAF) and Write-After-Free (WAF) conditions arise when kernel page table pages are freed and later reallocated. The IOMMU could misinterpret the new data as valid page table entries. The IOMMU might then walk into attacker-controlled memory, leading to arbitrary physical memory DMA access or privilege escalation. This is also a Write-After-Free issue, as the IOMMU will potentially continue to write Accessed and Dirty bits to the freed memory while attempting to walk the stale page tables.

Currently, SVA contexts are unprivileged and cannot access kernel mappings. However, the IOMMU will still walk kernel-only page tables all the way down to the leaf entries, where it realizes the mapping is for the kernel and errors out. This means the IOMMU still caches these intermediate page table entries, making the described vulnerability a real concern.

Disable SVA on x86 architecture until the IOMMU can receive notification to flush the paging cache before freeing the CPU kernel page table pages.

Affected products

Remediation

Red Hat statement

This is a significant security vulnerability affecting x86 systems with IOMMU SVA support enabled. While SVA contexts are unprivileged and cannot directly access kernel mappings, the IOMMU still walks and caches intermediate kernel page table entries. An attacker could potentially exploit the stale cache entries to gain arbitrary DMA access or escalate privileges. The fix disables SVA on x86 until proper cache invalidation mechanisms are implemented.

Metrics

Weaknesses (1)

CWE-820

References (11)

Change history (0)

No recorded changes yet.

Sources
CVE.org / MITRE
Status PUBLISHED
Assigner Linux
Published Jan 13, 2026
Updated Aug 5, 2026
Reserved Jan 13, 2026
Link CVE-2025-71089
CISA Vulnrichment
Updated Jun 16, 2026
NVD
Status Modified
Modified Jun 17, 2026
Link CVE-2025-71089
Red Hat
Severity Moderate
Public date Jan 13, 2026
Links CVE-2025-71089 - Bugzilla