Bug 2406776 (CVE-2025-40058)

Summary: CVE-2025-40058 kernel: iommu/vt-d: Disallow dirty tracking if incoherent page walk
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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A flaw was found in the Intel VT-d IOMMU support in the Linux kernel. When an IOMMU is configured to perform dirty-page tracking, but the page-walk memory region is incoherent between the IOMMU and CPU, the hardware may attempt to atomically update the bits in a paging-structure entry that is not properly snooped. The resulting fault could lead to a system hang and a non-recoverable state.
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Description OSIDB Bzimport 2025-10-28 12:04:56 UTC 
In the Linux kernel, the following vulnerability has been resolved:

iommu/vt-d: Disallow dirty tracking if incoherent page walk

Dirty page tracking relies on the IOMMU atomically updating the dirty bit
in the paging-structure entry. For this operation to succeed, the paging-
structure memory must be coherent between the IOMMU and the CPU. In
another word, if the iommu page walk is incoherent, dirty page tracking
doesn't work.

The Intel VT-d specification, Section 3.10 "Snoop Behavior" states:

"Remapping hardware encountering the need to atomically update A/EA/D bits
 in a paging-structure entry that is not snooped will result in a non-
 recoverable fault."

To prevent an IOMMU from being incorrectly configured for dirty page
tracking when it is operating in an incoherent mode, mark SSADS as
supported only when both ecap_slads and ecap_smpwc are supported.
Comment 1 Jon Moroney 2025-10-28 20:32:28 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025102815-CVE-2025-40058-0eba@gregkh/T
Comment 4 errata-xmlrpc 2025-12-01 10:39:12 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2025:22405 https://access.redhat.com/errata/RHSA-2025:22405
Comment 5 errata-xmlrpc 2025-12-08 14:42:23 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2025:22854 https://access.redhat.com/errata/RHSA-2025:22854