In the Linux kernel, the following vulnerability has been resolved:
KVM: SVM: Add missing save/restore handling of LBR MSRs
MSR_IA32_DEBUGCTLMSR and LBR MSRs are currently not enumerated by KVM_GET_MSR_INDEX_LIST, and LBR MSRs cannot be set with KVM_SET_MSRS. So save/restore is completely broken.
Fix it by adding the MSRs to msrs_to_save_base, and allowing writes to LBR MSRs from userspace only (as they are read-only MSRs) if LBR virtualization is enabled. Additionally, to correctly restore L1's LBRs while L2 is running, make sure the LBRs are copied from the captured VMCB01 save area in svm_copy_vmrun_state().
Note, for VMX, this also fixes a flaw where MSR_IA32_DEBUGCTLMSR isn't reported as an MSR to save/restore.
Note #2, over-reporting MSR_IA32_LASTxxx on Intel is ok, as KVM already handles unsupported reads and writes thanks to commit b5e2fec0ebc3 ("KVM: Ignore DEBUGCTL MSRs with no effect") (kvm_do_msr_access() will morph the unsupported userspace write into a nop).
[sean: guard with lbrv checks, massage changelog]
CVSS Details
- CVSS 3.1 Base Score: 5.5
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon_linux_2023 | — | Upgrade bpftool6.18-debuginfoUpgrade perf6.18Upgrade kernel6.18-debuginfo-common-x86_64Upgrade python3-perf6.18Upgrade perf6.18-debuginfoUpgrade kernel6.18-debuginfoUpgrade python3-perf6.18-debuginfoUpgrade bpftool6.18Upgrade kernel6.18-debuginfo-common-aarch64Upgrade kernel6.18-tools-debuginfoUpgrade kernel6.18-tools-develUpgrade kernel6.18-develUpgrade kernel6.18-toolsUpgrade kernel6.18-modules-extraUpgrade kernel6.18-headersUpgrade kernel-livepatch-6.18.30-61.116Upgrade kernel6.18Upgrade kernel6.18-modules-extra-common | Jun 23, 2026 | May 27, 2026 |
| Redhat_linux | — | No solution exists | Jul 17, 2026 | May 27, 2026 |
| Ubuntu | — | Upgrade linux-image-gcp-7.0Upgrade linux-image-oem-26.04Upgrade linux-image-7.0.0-1010-azureUpgrade linux-image-virtual-hwe-24.04Upgrade linux-image-7.0.0-1007-oracle-64kUpgrade linux-image-nvidia-7.0Upgrade linux-image-7.0.0-1009-azure-fdeUpgrade linux-image-nvidiaUpgrade linux-image-oem-24.04Upgrade linux-image-7.0.0-28-genericUpgrade linux-image-virtual-7.0Upgrade linux-image-virtual-hwe-26.04Upgrade linux-image-ibm-7.0Upgrade linux-image-raspi-realtime-7.0Upgrade linux-image-ibmUpgrade linux-image-7.0.0-1008-aws-64kUpgrade linux-image-7.0.0-1013-nvidiaUpgrade linux-image-aws-7.0Upgrade linux-image-oracle-64k-7.0Upgrade linux-image-realtime-7.0Upgrade linux-image-aws-64k-7.0Upgrade linux-image-virtualUpgrade linux-image-generic-64k-hwe-26.04Upgrade linux-image-7.0.0-28-generic-64kUpgrade linux-image-azure-fde-7.0Upgrade linux-image-aws-64kUpgrade linux-image-7.0.0-1007-gcp-64kUpgrade linux-image-oem-24.04bUpgrade linux-image-7.0.0-1007-oracleUpgrade linux-image-generic-64kUpgrade linux-image-7.0.0-1013-nvidia-64kUpgrade linux-image-nvidia-64k-7.0Upgrade linux-image-azure-fdeUpgrade linux-image-oracle-7.0Upgrade linux-image-7.0.0-1014-raspiUpgrade linux-image-7.0.0-1009-ibmUpgrade linux-image-7.0.0-1008-awsUpgrade linux-image-genericUpgrade linux-image-awsUpgrade linux-image-oracle-64kUpgrade linux-image-raspiUpgrade linux-image-7.0.0-27-realtimeUpgrade linux-image-realtimeUpgrade linux-image-nvidia-64kUpgrade linux-image-gcp-64k-7.0Upgrade linux-image-realtime-64k-hwe-26.04Upgrade linux-image-oem-24.04aUpgrade linux-image-generic-64k-7.0Upgrade linux-image-7.0.0-27-genericUpgrade linux-image-gcpUpgrade linux-image-7.0.0-27-generic-64kUpgrade linux-image-7.0.0-1008-oemUpgrade linux-image-oem-26.04aUpgrade linux-image-generic-64k-hwe-24.04Upgrade linux-image-oracleUpgrade linux-image-generic-hwe-24.04Upgrade linux-image-gcp-64kUpgrade linux-image-realtime-hwe-26.04Upgrade linux-image-realtime-64kUpgrade linux-image-raspi-7.0Upgrade linux-image-7.0.0-1014-raspi-realtimeUpgrade linux-image-oem-7.0Upgrade linux-image-oem-24.04dUpgrade linux-image-7.0.0-1007-gcpUpgrade linux-image-realtime-64k-7.0Upgrade linux-image-oem-24.04cUpgrade linux-image-7.0.0-27-realtime-64kUpgrade linux-image-azure-7.0Upgrade linux-image-azureUpgrade linux-image-generic-hwe-26.04Upgrade linux-image-generic-7.0Upgrade linux-image-raspi-realtime | Jul 1, 2026 | May 27, 2026 |
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