CVE-2025-38560: x86/sev: Evict cache lines during SNP memory validation
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 Fn8000001FEBX[31] defines the COHERENCYSFWNO 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 COHERENCYSFWNO bit is not set, indicating the SNP guest is vulnerable.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Implement/enable the mitigation by evicting cache lines during SNP memory validation: when validating a 4K page during a page state change to private, and the COHERENCY_SFW_NO CPUID bit (Fn8000001F_EBX[31]) is not set, touch the first and last byte of the 4K page being validated. When the COHERENCY_SFW_NO bit is set, skip the mitigation as no software mitigation is needed.
Linux kernel (x86/sev) SNP cache coherency mitigation (COHERENCY_SFW_NO CPUID bit Fn8000001F_EBX[31]) = Evict cache lines by touching the first and last byte of each 4K page only when COHERENCY_SFW_NO bit is not set
Event History
Frequently Asked Questions
What is the severity of CVE-2025-38560?
CVE-2025-38560 has been classified as a high-severity vulnerability due to its potential impact on system security.
How do I fix CVE-2025-38560?
To mitigate CVE-2025-38560, ensure that your Linux kernel is updated to the latest version that includes the fix.
What type of systems are affected by CVE-2025-38560?
CVE-2025-38560 affects systems running the Linux kernel that utilize Secure Nested Paging (SNP) for memory validation.
What is the nature of the vulnerability in CVE-2025-38560?
CVE-2025-38560 involves a cache coherency issue that requires cache line eviction during memory validation after a page state change.
Is there a recommended action for administrators regarding CVE-2025-38560?
Administrators should review their systems for the Linux kernel version and apply updates promptly to mitigate CVE-2025-38560.