KVM: x86: Fix the NULL pointer parameter in check_cr_write()

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>

1 files changed, 5 insertions, 3 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 16bf6655aa85..15f527b44aa7 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4102,10 +4102,12 @@ static int check_cr_write(struct x86_emulate_ctxt *ctxt)
                 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;