From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Christopherson Date: Thu, 15 Aug 2019 17:22:37 +0000 Subject: [PATCH] KVM: Assert that struct kvm_vcpu is always as offset zero Message-Id: <20190815172237.10464-1-sean.j.christopherson@intel.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Paul Mackerras , Joerg Roedel , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= Cc: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org 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 --- 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); -- 2.22.0