CVE-2025-38560

In the Linux kernel, the following vulnerability has been resolved:

x86/sev: Evict cache lines during SNP memory validation

An SNP cache coherency vulnerability requires a cache line eviction mitigation when validating memory after a page state change to private. The specific mitigation is to touch the first and last byte of each 4K page that is being validated. There is no need to perform the mitigation when performing a page state change to shared and rescinding validation.

CPUID bit Fn8000001F_EBX[31] defines the COHERENCY_SFW_NO CPUID bit that, when set, indicates that the software mitigation for this vulnerability is not needed.

Implement the mitigation and invoke it when validating memory (making it private) and the COHERENCY_SFW_NO bit is not set, indicating the SNP guest is vulnerable.

This vulnerability is rated as Moderate severity because exploitation is constrained to local access within specialized confidential computing environments, preventing remote compromise. The issue specifically impacts virtual machines running as AMD SEV-SNP guests on hardware that lacks the hardware-enforced cache coherency feature. Standard bare-metal installations and traditional virtual machine workloads not utilizing AMD SEV-SNP are not affected.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.