On x86, ARM and s390, struct kvm_vcpu_arch has a usercopy region taht is read and written by the KVM_GET/SET_CPUID2 ioctls (x86) or KVM_GET/SET_ONE_REG (ARM/s390). Without whitelisting the area, KVM is completely broken on those architectures with usercopy hardening enabled.
For now, allow writing to the entire struct on all architectures. The KVM tree will not refine this to an architecture-specific subset of struct kvm_vcpu_arch. Cc: [email protected] Cc: Kees Cook <[email protected]> Cc: Christian Borntraeger <[email protected]> Cc: Christoffer Dall <[email protected]> Cc: Radim Krčmář <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]> --- virt/kvm/kvm_main.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 4d81f6ded88e..b4809ccfdfa1 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4005,8 +4005,12 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, /* A kmem cache lets us meet the alignment requirements of fx_save. */ if (!vcpu_align) vcpu_align = __alignof__(struct kvm_vcpu); - kvm_vcpu_cache = kmem_cache_create("kvm_vcpu", vcpu_size, vcpu_align, - 0, NULL); + kvm_vcpu_cache = + kmem_cache_create_usercopy("kvm_vcpu", + sizeof(struct kvm_vcpu), vcpu_align, + 0, offsetof(struct kvm_vcpu, arch), + sizeof_field(struct kvm_vcpu, arch), + NULL); if (!kvm_vcpu_cache) { r = -ENOMEM; goto out_free_3; -- 2.14.2
