KVM: Assert that struct kvm_vcpu is always as offset zero

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@intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-08-15 10:22:37 -07:00 committed by Paolo Bonzini
parent b382f44e98
commit 12b58f4ed2
3 changed files with 9 additions and 0 deletions
arch
powerpc/kvm
x86/kvm

View File

@ -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;

View File

@ -2133,6 +2133,9 @@ 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;

View File

@ -6625,6 +6625,9 @@ 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);