[PATCH 4.16 07/43] kvm: nVMX: Enforce cpl=0 for VMX instructions

Greg Kroah-Hartman
2018-06-14T14:42:26Z

From: Felix Wilhelm <fwilhelm@google.com>

commit 727ba748e110b4de50d142edca9d6a9b7e6111d8 upstream.

VMX instructions executed inside a L1 VM will always trigger a VM exit
even when executed with cpl 3. This means we must perform the
privilege check in software.

Fixes: 70f3aac964ae("kvm: nVMX: Remove superfluous VMX instruction fault checks")
Cc: stable@vger.kernel.org
Signed-off-by: Felix Wilhelm <fwilhelm@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/vmx.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7426,6 +7426,12 @@ static int handle_vmon(struct kvm_vcpu *
return 1;
}

+ /* CPL=0 must be checked manually. */
+ if (vmx_get_cpl(vcpu)) {
+ kvm_queue_exception(vcpu, UD_VECTOR);
+ return 1;
+ }
+
if (vmx->nested.vmxon) {
nested_vmx_failValid(vcpu, VMXERR_VMXON_IN_VMX_ROOT_OPERATION);
return kvm_skip_emulated_instruction(vcpu);
@@ -7485,6 +7491,11 @@ static int handle_vmon(struct kvm_vcpu *
*/
static int nested_vmx_check_permission(struct kvm_vcpu *vcpu)
{
+ if (vmx_get_cpl(vcpu)) {
+ kvm_queue_exception(vcpu, UD_VECTOR);
+ return 0;
+ }
+
if (!to_vmx(vcpu)->nested.vmxon) {
kvm_queue_exception(vcpu, UD_VECTOR);
return 0;
@@ -7785,7 +7796,7 @@ static int handle_vmread(struct kvm_vcpu
if (get_vmx_mem_address(vcpu, exit_qualification,
vmx_instruction_info, true, &gva))
return 1;
- /* _system ok, as hardware has verified cpl=0 */
+ /* _system ok, nested_vmx_check_permission has verified cpl=0 */
kvm_write_guest_virt_system(&vcpu->arch.emulate_ctxt, gva,
&field_value, (is_long_mode(vcpu) ? 8 : 4), NULL);
}
@@ -7945,7 +7956,7 @@ static int handle_vmptrst(struct kvm_vcp
if (get_vmx_mem_address(vcpu, exit_qualification,
vmx_instruction_info, true, &vmcs_gva))
return 1;
- /* ok to use *_system, as hardware has verified cpl=0 */
+ /* *_system ok, nested_vmx_check_permission has verified cpl=0 */
if (kvm_write_guest_virt_system(&vcpu->arch.emulate_ctxt, vmcs_gva,
(void *)&to_vmx(vcpu)->nested.current_vmptr,
sizeof(u64), &e)) {