Commit d6500149 authored Sep 18, 2017 by Yu Zhang Committed by Radim Krčmář Sep 19, 2017

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: d1cd3ce9 ("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>

parent 95e2a3b3

arch/x86/kvm/emulate.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -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;