From patchwork Thu Apr 8 11:43:00 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Emanuele Giuseppe Esposito X-Patchwork-Id: 12190751 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 564F0C43460 for ; Thu, 8 Apr 2021 11:43:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 33C8B61155 for ; Thu, 8 Apr 2021 11:43:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231134AbhDHLns (ORCPT ); Thu, 8 Apr 2021 07:43:48 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:25259 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231310AbhDHLnr (ORCPT ); Thu, 8 Apr 2021 07:43:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617882216; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+OOkthL+koEr5R8pUMKCXf6426WciB8ikuZyFtZRx7o=; b=XV/hpKJCQumP4DzN04rKQOiyQlwemrBd4rc7KyvOC+vSRIEMm/3xCYn/7hLjzzhQeQz94m 3dti5OJyJmJ2AJ26ykFRwnWremmr4qPhBxkHtWngNGj9BWHucXLX29mseyuTz/Z2R2QHhN c8hBE8BBOrc6bzZf5fCKrJvtZI73bWU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-532-NXKLR0kxOXyBL5yjGG989g-1; Thu, 08 Apr 2021 07:43:32 -0400 X-MC-Unique: NXKLR0kxOXyBL5yjGG989g-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1B3A4801814; Thu, 8 Apr 2021 11:43:31 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-113-155.ams2.redhat.com [10.36.113.155]) by smtp.corp.redhat.com (Postfix) with ESMTP id A15E05B4A8; Thu, 8 Apr 2021 11:43:12 +0000 (UTC) From: Emanuele Giuseppe Esposito To: kvm@vger.kernel.org Cc: Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Emanuele Giuseppe Esposito , Jim Mattson , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Shuah Khan , Alexander Graf , Andrew Jones , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v4 1/4] KVM: x86: Fix a spurious -E2BIG in KVM_GET_EMULATED_CPUID Date: Thu, 8 Apr 2021 13:43:00 +0200 Message-Id: <20210408114303.30310-2-eesposit@redhat.com> In-Reply-To: <20210408114303.30310-1-eesposit@redhat.com> References: <20210408114303.30310-1-eesposit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org When retrieving emulated CPUID entries, check for an insufficient array size if and only if KVM is actually inserting an entry. If userspace has a priori knowledge of the exact array size, KVM_GET_EMULATED_CPUID will incorrectly fail due to effectively requiring an extra, unused entry. Fixes: 433f4ba19041 ("KVM: x86: fix out-of-bounds write in KVM_GET_EMULATED_CPUID (CVE-2019-19332)") Signed-off-by: Emanuele Giuseppe Esposito Reviewed-by: Sean Christopherson --- arch/x86/kvm/cpuid.c | 33 ++++++++++++++++----------------- 1 file changed, 16 insertions(+), 17 deletions(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 6bd2f8b830e4..d30194081892 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -567,34 +567,33 @@ static struct kvm_cpuid_entry2 *do_host_cpuid(struct kvm_cpuid_array *array, static int __do_cpuid_func_emulated(struct kvm_cpuid_array *array, u32 func) { - struct kvm_cpuid_entry2 *entry; - - if (array->nent >= array->maxnent) - return -E2BIG; + struct kvm_cpuid_entry2 entry; - entry = &array->entries[array->nent]; - entry->function = func; - entry->index = 0; - entry->flags = 0; + memset(&entry, 0, sizeof(entry)); switch (func) { case 0: - entry->eax = 7; - ++array->nent; + entry.eax = 7; break; case 1: - entry->ecx = F(MOVBE); - ++array->nent; + entry.ecx = F(MOVBE); break; case 7: - entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX; - entry->eax = 0; - entry->ecx = F(RDPID); - ++array->nent; - default: + entry.flags = KVM_CPUID_FLAG_SIGNIFCANT_INDEX; + entry.ecx = F(RDPID); break; + default: + goto out; } + /* This check is performed only when func is valid */ + if (array->nent >= array->maxnent) + return -E2BIG; + + entry.function = func; + memcpy(&array->entries[array->nent++], &entry, sizeof(entry)); + +out: return 0; }