From: Yu Zhang <yu.c.zhang@linux.intel.com>
Date: Mon, 18 Sep 2017 18:45:01 +0800
Subject: KVM: x86: Fix the NULL pointer parameter in check_cr_write()
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Patch-mainline: v4.14-rc2
Git-commit: d6500149bc4fddc5a91cd1a0c31b38fa36bff3ee
References: bsc#1077761

Routine check_cr_write() will trigger emulator_get_cpuid()->
kvm_cpuid() to get maxphyaddr, and NULL is passed as values
for ebx/ecx/edx. This is problematic because kvm_cpuid() will
dereference these pointers.

Fixes: d1cd3ce90044 ("KVM: MMU: check guest CR3 reserved bits based on its physical address width.")
Reported-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Acked-by: Alexander Graf <agraf@suse.de>
---
 arch/x86/kvm/emulate.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4102,10 +4102,12 @@
 		ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
 		if (efer & EFER_LMA) {
 			u64 maxphyaddr;
-			u32 eax = 0x80000008;
+			u32 eax, ebx, ecx, edx;
 
-			if (ctxt->ops->get_cpuid(ctxt, &eax, NULL, NULL,
-						 NULL, false))
+			eax = 0x80000008;
+			ecx = 0;
+			if (ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx,
+						 &edx, false))
 				maxphyaddr = eax & 0xff;
 			else
 				maxphyaddr = 36;