2021-11-15 14:08:52

by 黄乐

Subject: [PATCH v2] KVM: x86: Fix uninitialized eoi_exit_bitmap usage in vcpu_load_eoi_exitmap()

In vcpu_load_eoi_exitmap(), currently the eoi_exit_bitmap[4] array is
initialized only when Hyper-V context is available, in other path it is
just passed to kvm_x86_ops.load_eoi_exitmap() directly from on the stack,
which would cause unexpected interrupt delivery/handling issues, e.g. an
*old* linux kernel that relies on PIT to do clock calibration on KVM might
randomly fail to boot.

Fix it by passing ioapic_handled_vectors to load_eoi_exitmap() when Hyper-V
context is not available.

Fixes: f2bc14b69c38 ("KVM: x86: hyper-v: Prepare to meet unallocated Hyper-V context")
Cc: [email protected]
Reviewed-by: Vitaly Kuznetsov <[email protected]>
Signed-off-by: Huang Le <[email protected]>
---
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dc7eb5fddfd3..26466f94e31a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9547,12 +9547,16 @@ static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu)
if (!kvm_apic_hw_enabled(vcpu->arch.apic))
return;

- if (to_hv_vcpu(vcpu))
+ if (to_hv_vcpu(vcpu)) {
bitmap_or((ulong *)eoi_exit_bitmap,
vcpu->arch.ioapic_handled_vectors,
to_hv_synic(vcpu)->vec_bitmap, 256);
+ static_call(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
+ return;
+ }

- static_call(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
+ static_call(kvm_x86_load_eoi_exitmap)(
+ vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors);
}

void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,

2021-11-16 09:44:28

by Paolo Bonzini

Subject: Re: [PATCH v2] KVM: x86: Fix uninitialized eoi_exit_bitmap usage in vcpu_load_eoi_exitmap()

On 11/15/21 15:08, 黄乐 wrote:
> In vcpu_load_eoi_exitmap(), currently the eoi_exit_bitmap[4] array is
> initialized only when Hyper-V context is available, in other path it is
> just passed to kvm_x86_ops.load_eoi_exitmap() directly from on the stack,
> which would cause unexpected interrupt delivery/handling issues, e.g. an
> *old* linux kernel that relies on PIT to do clock calibration on KVM might
> randomly fail to boot.
>
> Fix it by passing ioapic_handled_vectors to load_eoi_exitmap() when Hyper-V
> context is not available.
>
> Fixes: f2bc14b69c38 ("KVM: x86: hyper-v: Prepare to meet unallocated Hyper-V context")
> Cc: [email protected]
> Reviewed-by: Vitaly Kuznetsov <[email protected]>
> Signed-off-by: Huang Le <[email protected]>
> ---
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index dc7eb5fddfd3..26466f94e31a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9547,12 +9547,16 @@ static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu)
> if (!kvm_apic_hw_enabled(vcpu->arch.apic))
> return;
>
> - if (to_hv_vcpu(vcpu))
> + if (to_hv_vcpu(vcpu)) {
> bitmap_or((ulong *)eoi_exit_bitmap,
> vcpu->arch.ioapic_handled_vectors,
> to_hv_synic(vcpu)->vec_bitmap, 256);
> + static_call(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
> + return;
> + }
>
> - static_call(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
> + static_call(kvm_x86_load_eoi_exitmap)(
> + vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors);
> }
>
> void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
>

Queued, thanks.

Paolo