releases/4.14.68/kvm-vmx-use-local-variable-for-current_vmptr-when-emulating-vmptrst.patch

From foo@baz Sun Aug 26 09:13:00 CEST 2018
From: Sean Christopherson <sean.j.christopherson@intel.com>
Date: Thu, 19 Jul 2018 10:31:00 -0700
Subject: KVM: vmx: use local variable for current_vmptr when emulating VMPTRST

From: Sean Christopherson <sean.j.christopherson@intel.com>

[ Upstream commit 0a06d4256674c4e041945b52044941995fee237d ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kvm/vmx.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8108,21 +8108,20 @@ static int handle_vmptrld(struct kvm_vcp
 /* 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;
 	}