CVE-2021-47062: KVM: SVM: Use online_vcpus, not created_vcpus, to iterate over vCPUs

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-02-29 · updated 2026-06-17
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Use online_vcpus, not created_vcpus, to iterate over vCPUs Use the kvm_for_each_vcpu() helper to iterate over vCPUs when encrypting VMSAs for SEV, which effectively switches to use online_vcpus instead of created_vcpus. This fixes a possible null-pointer dereference as created_vcpus does not guarantee a vCPU exists, since it is updated at the very beginning of KVM_CREATE_VCPU. created_vcpus exists to allow the bulk of vCPU creation to run in parallel, while still correctly restricting the max number of max vCPUs.

Affected products

Linux kernel: from 5.11 before 5.11.21; from 5.12 before 5.12.4 — fixed in 5.11.21, 5.12.4

How to fix

Upgrade to a fixed version: Linux kernel 5.11.21, 5.12.4. Check the vendor advisory for mitigations.

References

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