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KVM: svm: unconditionally intercept #DB

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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>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2015-11-10 09:14:39 +01:00
parent 54a20552e1
commit cbdb967af3
1 changed files with 3 additions and 11 deletions
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14
arch/x86/kvm/svm.c
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@ -1020,6 +1020,7 @@ 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);
@ -1554,20 +1555,13 @@ 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
@ -1673,7 +1667,6 @@ 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 &
@ -3661,7 +3654,6 @@ static void 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);
}
static int svm_set_tss_addr(struct kvm *kvm, unsigned int addr)
@ -4287,7 +4279,7 @@ 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,