Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Tue, 24 Nov 2015 22:33:59 +0000 | Subject | [PATCH 3.2 41/52] KVM: svm: unconditionally intercept #DB |
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3.2.74-rc1 review patch. If anyone has any objections, please let me know.
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From: Paolo Bonzini <pbonzini@redhat.com>
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> [bwh: Backported to 3.2: #DB and #BP did not share a function, and there is no operation pointer referring to it, so remove update_db_intercept() entirely] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- arch/x86/kvm/svm.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-)
--- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1015,6 +1015,7 @@ static void init_vmcb(struct vcpu_svm *s 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); @@ -1550,26 +1551,6 @@ static void svm_set_segment(struct kvm_v mark_dirty(svm->vmcb, VMCB_SEG); } -static void update_db_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 - vcpu->guest_debug = 0; -} - static void svm_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg) { struct vcpu_svm *svm = to_svm(vcpu); @@ -1580,8 +1561,6 @@ static void svm_guest_debug(struct kvm_v svm->vmcb->save.dr7 = vcpu->arch.dr7; mark_dirty(svm->vmcb, VMCB_DR); - - update_db_intercept(vcpu); } static void new_asid(struct vcpu_svm *svm, struct svm_cpu_data *sd) @@ -1655,7 +1634,6 @@ static int db_interception(struct vcpu_s if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP)) svm->vmcb->save.rflags &= ~(X86_EFLAGS_TF | X86_EFLAGS_RF); - update_db_intercept(&svm->vcpu); } if (svm->vcpu.guest_debug & @@ -3557,7 +3535,6 @@ static void enable_nmi_window(struct kvm */ svm->nmi_singlestep = true; svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF); - update_db_intercept(vcpu); } static int svm_set_tss_addr(struct kvm *kvm, unsigned int addr)
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