Linux Kernel CVE-2025-40058

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.

The affected product is the Linux kernel Intel VT-d IOMMU driver (iommu/vt-d, second-stage dirty tracking / SSADS path). No CPE strings were provided in the intelligence, and specific vulnerable version ranges are not enumerated in the input; the three referenced stable-tree commits (git.kernel.org/stable/c/57f55048e564dedd8a4546d018e29d6bbfff0a7e, /8d096ce0e87bdc361f0b25d7943543bc53aa0b9e, and /ebe16d245a00626bb87163862a1b07daf5475a3e) indicate the fix was backported across multiple stable branches, implying multiple kernel versions supporting VT-d dirty tracking are affected until patched. Only systems using Intel VT-d hardware with second-stage dirty page tracking are practically impacted.