From: Vitaly Kuznetsov vkuznets@redhat.com
commit 95fa10103dabc38be5de8efdfced5e67576ed896 upstream.
When an EVMCS enabled L1 guest on KVM will tries doing enlightened VMEnter with EVMCS GPA = 0 the host crashes because the
evmcs_gpa != vmx->nested.hv_evmcs_vmptr
condition in nested_vmx_handle_enlightened_vmptrld() will evaluate to false (as nested.hv_evmcs_vmptr is zeroed after init). The crash will happen on vmx->nested.hv_evmcs pointer dereference.
Another problematic EVMCS ptr value is '-1' but it only causes host crash after nested_release_evmcs() invocation. The problem is exactly the same as with '0', we mistakenly think that the EVMCS pointer hasn't changed and thus nested.hv_evmcs_vmptr is valid.
Resolve the issue by adding an additional !vmx->nested.hv_evmcs check to nested_vmx_handle_enlightened_vmptrld(), this way we will always be trying kvm_vcpu_map() when nested.hv_evmcs is NULL and this is supposed to catch all invalid EVMCS GPAs.
Also, initialize hv_evmcs_vmptr to '0' in nested_release_evmcs() to be consistent with initialization where we don't currently set hv_evmcs_vmptr to '-1'.
Cc: stable@vger.kernel.org Signed-off-by: Vitaly Kuznetsov vkuznets@redhat.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/vmx/nested.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -223,7 +223,7 @@ static inline void nested_release_evmcs( return;
kvm_vcpu_unmap(vcpu, &vmx->nested.hv_evmcs_map, true); - vmx->nested.hv_evmcs_vmptr = -1ull; + vmx->nested.hv_evmcs_vmptr = 0; vmx->nested.hv_evmcs = NULL; }
@@ -1828,7 +1828,8 @@ static int nested_vmx_handle_enlightened if (!nested_enlightened_vmentry(vcpu, &evmcs_gpa)) return 1;
- if (unlikely(evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) { + if (unlikely(!vmx->nested.hv_evmcs || + evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) { if (!vmx->nested.hv_evmcs) vmx->nested.current_vmptr = -1ull;