On 15/08/19 19:22, Sean Christopherson wrote:
> KVM implementations that wrap struct kvm_vcpu with a vendor specific
> struct, e.g. struct vcpu_vmx, must place the vcpu member at offset 0,
> otherwise the usercopy region intended to encompass struct kvm_vcpu_arch
> will instead overlap random chunks of the vendor specific struct.
> E.g. padding a large number of bytes before struct kvm_vcpu triggers
> a usercopy warn when running with CONFIG_HARDENED_USERCOPY=y.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
>
> Note, the PowerPC change is completely untested.
>
> arch/powerpc/kvm/e500.c | 3 +++
> arch/x86/kvm/svm.c | 3 +++
> arch/x86/kvm/vmx/vmx.c | 3 +++
> 3 files changed, 9 insertions(+)
>
> diff --git a/arch/powerpc/kvm/e500.c b/arch/powerpc/kvm/e500.c
> index b5a848a55504..00649ca5fa9a 100644
> --- a/arch/powerpc/kvm/e500.c
> +++ b/arch/powerpc/kvm/e500.c
> @@ -440,6 +440,9 @@ static struct kvm_vcpu *kvmppc_core_vcpu_create_e500(struct kvm *kvm,
> struct kvm_vcpu *vcpu;
> int err;
>
> + BUILD_BUG_ON_MSG(offsetof(struct kvmppc_vcpu_e500, vcpu) != 0,
> + "struct kvm_vcpu must be at offset 0 for arch usercopy region");
> +
> vcpu_e500 = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL);
> if (!vcpu_e500) {
> err = -ENOMEM;
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index d685491fce4d..70015ae5fc19 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2137,6 +2137,9 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
> struct page *nested_msrpm_pages;
> int err;
>
> + BUILD_BUG_ON_MSG(offsetof(struct vcpu_svm, vcpu) != 0,
> + "struct kvm_vcpu must be at offset 0 for arch usercopy region");
> +
> svm = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL_ACCOUNT);
> if (!svm) {
> err = -ENOMEM;
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 42ed3faa6af8..402cf2fe5cdd 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6615,6 +6615,9 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> unsigned long *msr_bitmap;
> int cpu;
>
> + BUILD_BUG_ON_MSG(offsetof(struct vcpu_vmx, vcpu) != 0,
> + "struct kvm_vcpu must be at offset 0 for arch usercopy region");
> +
> vmx = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL_ACCOUNT);
> if (!vmx)
> return ERR_PTR(-ENOMEM);
>
Queued, thanks.
Paolo
