KVM: SVM: Use online_vcpus, not created_vcpus, to iterate over vCPUs

Vulnerability 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.

References

• https://git.kernel.org/stable/c/bd0cced2ae93195668f983d443f7f17e8efd24d2
• https://git.kernel.org/stable/c/ba7bf5d6336aa9c0d977b161bfa420c56d46ee40
• https://git.kernel.org/stable/c/c36b16d29f3af5f32fc1b2a3401bf48f71cabee1