Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH 3.12 67/72] KVM: svm: unconditionally intercept #DB | Date | Mon, 23 Nov 2015 14:12:28 +0100 |
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From: Paolo Bonzini <pbonzini@redhat.com>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit cbdb967af3d54993f5814f1cee0ed311a055377d upstream.
This is needed to avoid the possibility that the guest triggers an infinite stream of #DB exceptions (CVE-2015-8104).
VMX is not affected: because it does not save DR6 in the VMCS, it already intercepts #DB unconditionally.
Reported-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Jiri Slaby <jslaby@suse.cz> --- arch/x86/kvm/svm.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index db4108b82e6b..289897326da4 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1104,6 +1104,7 @@ static void init_vmcb(struct vcpu_svm *svm) set_exception_intercept(svm, UD_VECTOR); set_exception_intercept(svm, MC_VECTOR); set_exception_intercept(svm, AC_VECTOR); + set_exception_intercept(svm, DB_VECTOR); set_intercept(svm, INTERCEPT_INTR); set_intercept(svm, INTERCEPT_NMI); @@ -1640,20 +1641,13 @@ static void svm_set_segment(struct kvm_vcpu *vcpu, mark_dirty(svm->vmcb, VMCB_SEG); } -static void update_db_bp_intercept(struct kvm_vcpu *vcpu) +static void update_bp_intercept(struct kvm_vcpu *vcpu) { struct vcpu_svm *svm = to_svm(vcpu); - clr_exception_intercept(svm, DB_VECTOR); clr_exception_intercept(svm, BP_VECTOR); - if (svm->nmi_singlestep) - set_exception_intercept(svm, DB_VECTOR); - if (vcpu->guest_debug & KVM_GUESTDBG_ENABLE) { - if (vcpu->guest_debug & - (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP)) - set_exception_intercept(svm, DB_VECTOR); if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) set_exception_intercept(svm, BP_VECTOR); } else @@ -1731,7 +1725,6 @@ static int db_interception(struct vcpu_svm *svm) if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP)) svm->vmcb->save.rflags &= ~(X86_EFLAGS_TF | X86_EFLAGS_RF); - update_db_bp_intercept(&svm->vcpu); } if (svm->vcpu.guest_debug & @@ -3681,7 +3674,6 @@ static int enable_nmi_window(struct kvm_vcpu *vcpu) */ svm->nmi_singlestep = true; svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF); - update_db_bp_intercept(vcpu); return 0; } @@ -4283,7 +4275,7 @@ static struct kvm_x86_ops svm_x86_ops = { .vcpu_load = svm_vcpu_load, .vcpu_put = svm_vcpu_put, - .update_db_bp_intercept = update_db_bp_intercept, + .update_db_bp_intercept = update_bp_intercept, .get_msr = svm_get_msr, .set_msr = svm_set_msr, .get_segment_base = svm_get_segment_base, -- 2.6.3
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