Message ID | 20210926015545.281083-1-zhenzhong.duan@intel.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | [v2] KVM: VMX: Fix a TSX_CTRL_CPUID_CLEAR field mask issue | expand |
On 26/09/21 03:55, Zhenzhong Duan wrote: > When updating the host's mask for its MSR_IA32_TSX_CTRL user return entry, > clear the mask in the found uret MSR instead of vmx->guest_uret_msrs[i]. > Modifying guest_uret_msrs directly is completely broken as 'i' does not > point at the MSR_IA32_TSX_CTRL entry. In fact, it's guaranteed to be an > out-of-bounds accesses as is always set to kvm_nr_uret_msrs in a prior > loop. By sheer dumb luck, the fallout is limited to "only" failing to > preserve the host's TSX_CTRL_CPUID_CLEAR. The out-of-bounds access is > benign as it's guaranteed to clear a bit in a guest MSR value, which are > always zero at vCPU creation on both x86-64 and i386. > > Cc: stable@vger.kernel.org > Fixes: 8ea8b8d6f869 ("KVM: VMX: Use common x86's uret MSR list as the one true list") > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com> > Reviewed-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/vmx/vmx.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 0c2c0d5ae873..cbf3d33432b9 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -6833,7 +6833,7 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu) > */ > tsx_ctrl = vmx_find_uret_msr(vmx, MSR_IA32_TSX_CTRL); > if (tsx_ctrl) > - vmx->guest_uret_msrs[i].mask = ~(u64)TSX_CTRL_CPUID_CLEAR; > + tsx_ctrl->mask = ~(u64)TSX_CTRL_CPUID_CLEAR; > } > > err = alloc_loaded_vmcs(&vmx->vmcs01); > Queued, thanks. Paolo
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 0c2c0d5ae873..cbf3d33432b9 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6833,7 +6833,7 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu) */ tsx_ctrl = vmx_find_uret_msr(vmx, MSR_IA32_TSX_CTRL); if (tsx_ctrl) - vmx->guest_uret_msrs[i].mask = ~(u64)TSX_CTRL_CPUID_CLEAR; + tsx_ctrl->mask = ~(u64)TSX_CTRL_CPUID_CLEAR; } err = alloc_loaded_vmcs(&vmx->vmcs01);