From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A73C3C61DA4 for ; Wed, 15 Mar 2023 20:16:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232286AbjCOUQ1 (ORCPT ); Wed, 15 Mar 2023 16:16:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230404AbjCOUQY (ORCPT ); Wed, 15 Mar 2023 16:16:24 -0400 Received: from mail-pf1-x44a.google.com (mail-pf1-x44a.google.com [IPv6:2607:f8b0:4864:20::44a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2957D1C59B for ; Wed, 15 Mar 2023 13:16:23 -0700 (PDT) Received: by mail-pf1-x44a.google.com with SMTP id bx9-20020a056a00428900b005f077bc6e5eso10640300pfb.16 for ; Wed, 15 Mar 2023 13:16:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1678911382; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=R+bS/HSfiAIHzE1BljlnDMwqBXmxYFJcJWZOF0Wd5Po=; b=NQSaosRVx7/zJnHPOvPspt/DVRn9KA0UI4unMES9kdaXIokpuLeqGmrxs1+XmvSbIO 5e0srJHpzbwz/51km5OPbT/IpYUqBxUHPJHiUgKVgAEtfRSw26SkQVLdnbkdJS7DOr7b X+tmzMkiSr0hIJhUBQSWSnGaErb5V3FLxZeL+g+LxXN/QmlSSiBNBsal3e0dk9s4XhfV qXYN074HQtUTLJrsu5SbxnQUg+lnA8lWDygSMNJCyU9MlvDQX529VJX2/LGClol3tD3j 3ZyuBXUjirYTayjDZg6HdTg3OTYcFx0xzKu5mAL19sKIzS+L/LqeXcnQ3IlwPW8yrPnf BU1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678911382; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=R+bS/HSfiAIHzE1BljlnDMwqBXmxYFJcJWZOF0Wd5Po=; b=U2KQrvWNUBdp2tsdQ59h7k7VoLNld/F7N2iKUq4CGMBIXtiBdU5wI6e3HRak/1AEfd ZGJTG2xYpwLP2ZeIQgZCiZ//fZL7AsTpQx3hejNqPkpORDV1xLbsrFVy+63yZQGDZ9OL GP4GKTxqfmkTNKUJ36kyzldfR9P87K7Mq1M92gJBpTEftp+ZZ9scgEBjgEK4dkiP5Qw6 YefzlzezhgoR9v74kdRXB1nGO6WRRk37NdYbWB/cSnv0CM2iJVmEdgJ6OTtCn9dTa5yV aDIqxU9sP2u5FDfmzhte0PvrPyrKtsLrXf+SHRfKtlex2HGcxBwTkSggBwNy0nrP7SPs LStg== X-Gm-Message-State: AO0yUKWIY1HHgz+xYM0+mpVnHT8yRKIUCDrE7oeagj4VfIxJ5fr4O6wH wxqa1YaNKIM5hYgMWlaKgZmZE9XNu70= X-Google-Smtp-Source: AK7set9Irl7M5X5NC/b6sLZ7p9ye1h2toPeT8JP5dVktiq1PORJ5Qojyyw3FCdmadm4BXHbZV4wJJokOQoA= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a65:6386:0:b0:4fb:a38d:c09b with SMTP id h6-20020a656386000000b004fba38dc09bmr140169pgv.10.1678911382440; Wed, 15 Mar 2023 13:16:22 -0700 (PDT) Date: Wed, 15 Mar 2023 13:16:20 -0700 In-Reply-To: <20230315195109.580333-1-d-tatianin@yandex-team.ru> Mime-Version: 1.0 References: <20230315195109.580333-1-d-tatianin@yandex-team.ru> Message-ID: Subject: Re: [PATCH] kvm/x86: actually verify that reading MSR_IA32_UCODE_REV succeeds From: Sean Christopherson To: Daniil Tatianin Cc: Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 15, 2023, Daniil Tatianin wrote: > ...and return KVM_MSR_RET_INVALID otherwise. > > Found by Linux Verification Center (linuxtesting.org) with the SVACE > static analysis tool. > > Fixes: cd28325249a1 ("KVM: VMX: support MSR_IA32_ARCH_CAPABILITIES as a feature MSR") > Signed-off-by: Daniil Tatianin > --- > arch/x86/kvm/x86.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 7713420abab0..7de6939fc371 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1661,7 +1661,8 @@ static int kvm_get_msr_feature(struct kvm_msr_entry *msr) > msr->data = kvm_caps.supported_perf_cap; > break; > case MSR_IA32_UCODE_REV: > - rdmsrl_safe(msr->index, &msr->data); > + if (rdmsrl_safe(msr->index, &msr->data)) > + return KVM_MSR_RET_INVALID; This is unnecessary and would arguably break KVM's ABI. KVM unconditionally emulates MSR_IA32_UCODE_REV in software and rdmsrl_safe() zeros the result on a fault (see ex_handler_msr()). '0' is a legitimate ucode revid and a reasonable fallback for a theoretical (virtual) CPU that doesn't support the MSR.