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Date: Mon, 18 Sep 2017 18:45:01 +0800 From: Yu Zhang <yu.c.zhang@...ux.intel.com> To: kvm@...r.kernel.org Cc: linux-kernel@...r.kernel.org, pbonzini@...hat.com, jmattson@...gle.com, rkrcmar@...hat.com, tglx@...utronix.de, mingo@...hat.com, hpa@...or.com Subject: [PATCH] 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@...gle.com> Signed-off-by: Yu Zhang <yu.c.zhang@...ux.intel.com> --- 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; -- 2.5.0
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