It was found that KVM virtualizing another hypervisor as L1 VM does not verify that VMX instructions from L1 VM (which trigger a VM exit and are emulated by L0 KVM) are coming from ring 0. This means that a normal user space program running in the L1 VM can trigger KVMs VMX emulation which gives a large number of privilege escalation vectors. This issue happens only if L2 guest is running, since VMX emulation code checks for the guests CR4.VMXE value.
This allows attacker in L2 guest to break out e.g. by exploiting a bug in L1 qemu process and using this bug for privilege escalation on the L1 system.
Created kernel tracking bugs for this issue:
Affects: fedora-all [bug 1595146]
CVE known via:
This issue does not affect the versions of the kernel package as shipped with
Red Hat Enterprise Linux 5, 6, 7 and Red Hat Enterprise MRG 2.
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):