KVM: vmx: use local variable for current_vmptr when emulating VMPTRST

Do not expose the address of vmx->nested.current_vmptr to
kvm_write_guest_virt_system() as the resulting __copy_to_user()
call will trigger a WARN when CONFIG_HARDENED_USERCOPY is
enabled.

Opportunistically clean up variable names in handle_vmptrst()
to improve readability, e.g. vmcs_gva is misleading as the
memory operand of VMPTRST is plain memory, not a VMCS.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Tested-by: Peter Shier <pshier@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 7 insertions, 8 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e30da9a2430c..548bef5359e6 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8480,21 +8480,20 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu)
 /* Emulate the VMPTRST instruction */
 static int handle_vmptrst(struct kvm_vcpu *vcpu)
 {
-        unsigned long exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
-        u32 vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
-        gva_t vmcs_gva;
+        unsigned long exit_qual = vmcs_readl(EXIT_QUALIFICATION);
+        u32 instr_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+        gpa_t current_vmptr = to_vmx(vcpu)->nested.current_vmptr;
         struct x86_exception e;
+        gva_t gva;
 
         if (!nested_vmx_check_permission(vcpu))
                 return 1;
 
-        if (get_vmx_mem_address(vcpu, exit_qualification,
-                        vmx_instruction_info, true, &vmcs_gva))
+        if (get_vmx_mem_address(vcpu, exit_qual, instr_info, true, &gva))
                 return 1;
         /* *_system ok, nested_vmx_check_permission has verified cpl=0 */
-        if (kvm_write_guest_virt_system(vcpu, vmcs_gva,
-                                        (void *)&to_vmx(vcpu)->nested.current_vmptr,
-                                        sizeof(u64), &e)) {
+        if (kvm_write_guest_virt_system(vcpu, gva, (void *)&current_vmptr,
+                                        sizeof(gpa_t), &e)) {
                 kvm_inject_page_fault(vcpu, &e);
                 return 1;
         }