From 0a32cd3d6adbe5cbfdfb411e1b1fccceec75e36a Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Tue, 1 Sep 2009 12:03:25 +0300 Subject: [PATCH] KVM: VMX: Check cpl before emulating debug register access commit 0a79b009525b160081d75cef5dbf45817956acf2 upstream. Debug registers may only be accessed from cpl 0. Unfortunately, vmx will code to emulate the instruction even though it was issued from guest userspace, possibly leading to an unexpected trap later. Signed-off-by: Avi Kivity Signed-off-by: Marcelo Tosatti Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/vmx.c | 3 +++ arch/x86/kvm/x86.c | 13 +++++++++++++ include/asm-x86/kvm_host.h | 1 + 3 files changed, 17 insertions(+) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 4cee61a464e47..7981dbe4eecb2 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2464,6 +2464,9 @@ static int handle_dr(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) unsigned long val; int dr, reg; + if (!kvm_require_cpl(vcpu, 0)) + return 1; + /* * FIXME: this code assumes the host is debugging the guest. * need to deal with guest debugging itself too. diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index bf872f2728907..994722494215c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -197,6 +197,19 @@ static void __queue_exception(struct kvm_vcpu *vcpu) vcpu->arch.exception.error_code); } +/* + * Checks if cpl <= required_cpl; if true, return true. Otherwise queue + * a #GP and return false. + */ +bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl) +{ + if (kvm_x86_ops->get_cpl(vcpu) <= required_cpl) + return true; + kvm_queue_exception_e(vcpu, GP_VECTOR, 0); + return false; +} +EXPORT_SYMBOL_GPL(kvm_require_cpl); + /* * Load the pae pdptrs. Return true is they are all valid. */ diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h index cf7c887165c4e..69d4de9b2bbc2 100644 --- a/include/asm-x86/kvm_host.h +++ b/include/asm-x86/kvm_host.h @@ -537,6 +537,7 @@ void kvm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr); void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code); void kvm_inject_page_fault(struct kvm_vcpu *vcpu, unsigned long cr2, u32 error_code); +bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl); void kvm_inject_nmi(struct kvm_vcpu *vcpu); -- 2.47.3