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authorLiran Alon <liran.alon@oracle.com>2018-06-29 22:59:04 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2018-07-18 11:31:28 +0200
commit2307af1c4b2e0ad886f30e31739845322cbd328b (patch)
treea2dd40049c5d7613e1c71afceb9c6ee51713b2c3
parentKVM: irqfd: fix race between EPOLLHUP and irq_bypass_register_consumer (diff)
downloadlinux-dev-2307af1c4b2e0ad886f30e31739845322cbd328b.tar.xz
linux-dev-2307af1c4b2e0ad886f30e31739845322cbd328b.zip
KVM: VMX: Mark VMXArea with revision_id of physical CPU even when eVMCS enabled
When eVMCS is enabled, all VMCS allocated to be used by KVM are marked with revision_id of KVM_EVMCS_VERSION instead of revision_id reported by MSR_IA32_VMX_BASIC. However, even though not explictly documented by TLFS, VMXArea passed as VMXON argument should still be marked with revision_id reported by physical CPU. This issue was found by the following setup: * L0 = KVM which expose eVMCS to it's L1 guest. * L1 = KVM which consume eVMCS reported by L0. This setup caused the following to occur: 1) L1 execute hardware_enable(). 2) hardware_enable() calls kvm_cpu_vmxon() to execute VMXON. 3) L0 intercept L1 VMXON and execute handle_vmon() which notes vmxarea->revision_id != VMCS12_REVISION and therefore fails with nested_vmx_failInvalid() which sets RFLAGS.CF. 4) L1 kvm_cpu_vmxon() don't check RFLAGS.CF for failure and therefore hardware_enable() continues as usual. 5) L1 hardware_enable() then calls ept_sync_global() which executes INVEPT. 6) L0 intercept INVEPT and execute handle_invept() which notes !vmx->nested.vmxon and thus raise a #UD to L1. 7) Raised #UD caused L1 to panic. Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com> Cc: stable@vger.kernel.org Fixes: 773e8a0425c923bc02668a2d6534a5ef5a43cc69 Signed-off-by: Liran Alon <liran.alon@oracle.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/vmx.c27
1 files changed, 21 insertions, 6 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ba981459d706..c3c85908b8de 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4108,11 +4108,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
vmcs_conf->order = get_order(vmcs_conf->size);
vmcs_conf->basic_cap = vmx_msr_high & ~0x1fff;
- /* KVM supports Enlightened VMCS v1 only */
- if (static_branch_unlikely(&enable_evmcs))
- vmcs_conf->revision_id = KVM_EVMCS_VERSION;
- else
- vmcs_conf->revision_id = vmx_msr_low;
+ vmcs_conf->revision_id = vmx_msr_low;
vmcs_conf->pin_based_exec_ctrl = _pin_based_exec_control;
vmcs_conf->cpu_based_exec_ctrl = _cpu_based_exec_control;
@@ -4182,7 +4178,13 @@ static struct vmcs *alloc_vmcs_cpu(int cpu)
return NULL;
vmcs = page_address(pages);
memset(vmcs, 0, vmcs_config.size);
- vmcs->revision_id = vmcs_config.revision_id; /* vmcs revision id */
+
+ /* KVM supports Enlightened VMCS v1 only */
+ if (static_branch_unlikely(&enable_evmcs))
+ vmcs->revision_id = KVM_EVMCS_VERSION;
+ else
+ vmcs->revision_id = vmcs_config.revision_id;
+
return vmcs;
}
@@ -4341,6 +4343,19 @@ static __init int alloc_kvm_area(void)
return -ENOMEM;
}
+ /*
+ * When eVMCS is enabled, alloc_vmcs_cpu() sets
+ * vmcs->revision_id to KVM_EVMCS_VERSION instead of
+ * revision_id reported by MSR_IA32_VMX_BASIC.
+ *
+ * However, even though not explictly documented by
+ * TLFS, VMXArea passed as VMXON argument should
+ * still be marked with revision_id reported by
+ * physical CPU.
+ */
+ if (static_branch_unlikely(&enable_evmcs))
+ vmcs->revision_id = vmcs_config.revision_id;
+
per_cpu(vmxarea, cpu) = vmcs;
}
return 0;