From d6500149bc4fddc5a91cd1a0c31b38fa36bff3ee Mon Sep 17 00:00:00 2001 From: Yu Zhang Date: Mon, 18 Sep 2017 18:45:01 +0800 Subject: [PATCH] KVM: x86: Fix the NULL pointer parameter in check_cr_write() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Yu Zhang Reviewed-by: David Hildenbrand Reviewed-by: Jim Mattson Signed-off-by: Radim Krčmář --- arch/x86/kvm/emulate.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 16bf665..15f527b 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; -- 2.7.4