CVE-2025-40058: Undefined Security Weakness

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.