From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753298AbdJ3Xv4 (ORCPT ); Mon, 30 Oct 2017 19:51:56 -0400 Received: from mail-io0-f195.google.com ([209.85.223.195]:56767 "EHLO mail-io0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752571AbdJ3Xvy (ORCPT ); Mon, 30 Oct 2017 19:51:54 -0400 X-Google-Smtp-Source: ABhQp+R5GBMI27eGfETet3V5suSXdIQ7N72Uo+82jqLJd5u5dMJggUah0PHswFaftBBvfsYWTi7s8znH3rnl8tW6POE= MIME-Version: 1.0 In-Reply-To: <20171030232849.GA8409@gmail.com> References: <20171026134547.23664-1-pbonzini@redhat.com> <20171026134547.23664-2-pbonzini@redhat.com> <20171030232849.GA8409@gmail.com> From: Kees Cook Date: Mon, 30 Oct 2017 16:51:52 -0700 X-Google-Sender-Auth: 9ZwrHqWv235vGqLgJ1jigOCM1yQ Message-ID: Subject: Re: [kernel-hardening] [PATCH 1/2] kvm: whitelist struct kvm_vcpu_arch To: Eric Biggers Cc: Paolo Bonzini , LKML , KVM , Christoffer Dall , Marc Zyngier , Christian Borntraeger , Cornelia Huck , James Hogan , Paul Mackerras , kernel-hardening@lists.openwall.com, Christian Borntraeger , Christoffer Dall , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v9UNq0jx012000 On Mon, Oct 30, 2017 at 4:28 PM, Eric Biggers wrote: > On Thu, Oct 26, 2017 at 03:45:46PM +0200, Paolo Bonzini wrote: >> 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: kernel-hardening@lists.openwall.com >> Cc: Kees Cook >> Cc: Christian Borntraeger >> Cc: Christoffer Dall >> Cc: Radim Krčmář >> Signed-off-by: Paolo Bonzini >> --- >> 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); > > Doesn't it need to be 'vcpu_size' instead of 'sizeof(struct kvm_vcpu)'? Oh, yikes, yes. $ git grep '\bkvm_init(' arch/mips/kvm/mips.c: ret = kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE); arch/powerpc/kvm/book3s.c: r = kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE); arch/powerpc/kvm/e500.c: r = kvm_init(NULL, sizeof(struct kvmppc_vcpu_e500), 0, THIS_MODULE); arch/powerpc/kvm/e500mc.c: r = kvm_init(NULL, sizeof(struct kvmppc_vcpu_e500), 0, THIS_MODULE); arch/s390/kvm/kvm-s390.c: return kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE); arch/x86/kvm/svm.c: return kvm_init(&svm_x86_ops, sizeof(struct vcpu_svm), arch/x86/kvm/vmx.c: int r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx), include/linux/kvm_host.h:int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align, virt/kvm/arm/arm.c: int rc = kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE); I'll fix this up. -Kees -- Kees Cook Pixel Security