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 X-Spam-Level: X-Spam-Status: No, score=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 D7771C433E0 for ; Tue, 12 Jan 2021 16:55:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8762723135 for ; Tue, 12 Jan 2021 16:55:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390816AbhALQys (ORCPT ); Tue, 12 Jan 2021 11:54:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390516AbhALQys (ORCPT ); Tue, 12 Jan 2021 11:54:48 -0500 Received: from mail-pj1-x1029.google.com (mail-pj1-x1029.google.com [IPv6:2607:f8b0:4864:20::1029]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 57D5AC061795 for ; Tue, 12 Jan 2021 08:54:07 -0800 (PST) Received: by mail-pj1-x1029.google.com with SMTP id b5so2048444pjk.2 for ; Tue, 12 Jan 2021 08:54:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=BvNPTfqT/5f4cwjyqGfBMaYw7woP/GveWw32QYUqvjQ=; b=m8vzTv31OLpB/Cx5Y7zqFtD1Mg1Ek0UYCQUnr2j8V7D+AXHUCqTa/U5XPzKqj56C1A KBQb7IbW9vKAUk11kd/UY2LKV4ipQijWbWIOShsmgx+Y0TWrzXgKtz+C3eeybAeZ5Bjw 2/Mi2/orPtgb6Ezypwnixca4ZUv2FPG6xyKU9Zzry9TA7EwxugDm0HCqeZdBbTv42ziZ 1uKFv5F9SzNVPL+ksK08s5q/Gp16+78QSSROeE+/YoG+Z6Y0C13LgnR40ua+ilJ8uFXf i1w7ED7IlE6sOnGL3yfMYWFVmcXFwPxFEMisoFK/3a+XAhYUaeZWODvqj+oSC9VaT9GK C6XA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=BvNPTfqT/5f4cwjyqGfBMaYw7woP/GveWw32QYUqvjQ=; b=PcM5BVdIb6IflTnPgRdon3U+am0HTw/mHZylErkziaOwgNM7HePI4pMNhoBb+fhkUX 5u6HvezmBrbReFlkx0CgY8MlcH5pVQkZMtMwfGLJvFQHRw/BXkIDGVdYbq6MRBAaT9vz wjIF82cLXml23vvveYCCvx0noRS6yyTl0KDFO5VO+dArrQJxPdic72SErL05Hy6/I99B zfa6r4rkgTRHgWUdgVK5AWZXRcq99Nm09ooxKrjiZvNS618I3nY6k5ZT3qHs8v0d/UER rLSmuLVY9NESiE6OLWL7xDq7LdfmP6NmjW1rlh2aQ7YwkqX645CGtgn06JxQ1vyzYg0/ I2qw== X-Gm-Message-State: AOAM532iUu24jjiYaa4wTkJ+pHL5+Ljp5mMlIKPWZXcf79p8W2mREqr3 4/nrwgr9CXtUX8zzlHzwcw8xRQ== X-Google-Smtp-Source: ABdhPJyDT2FjXRhiezNWphPPvJWhCSrfs/NCvloIzCEVdKgu+rtZoKa3mNCAs3vrPbn9eMtLMSYZQQ== X-Received: by 2002:a17:902:ee83:b029:da:3483:3957 with SMTP id a3-20020a170902ee83b02900da34833957mr92959pld.38.1610470446670; Tue, 12 Jan 2021 08:54:06 -0800 (PST) Received: from google.com ([2620:15c:f:10:1ea0:b8ff:fe73:50f5]) by smtp.gmail.com with ESMTPSA id 21sm3742730pfx.84.2021.01.12.08.54.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Jan 2021 08:54:05 -0800 (PST) Date: Tue, 12 Jan 2021 08:53:59 -0800 From: Sean Christopherson To: Paolo Bonzini Cc: Jim Mattson , syzbot , Borislav Petkov , "H . Peter Anvin" , Joerg Roedel , kvm list , LKML , Ingo Molnar , syzkaller-bugs , Thomas Gleixner , Vitaly Kuznetsov , Wanpeng Li , the arch/x86 maintainers Subject: Re: UBSAN: shift-out-of-bounds in kvm_vcpu_after_set_cpuid Message-ID: References: <000000000000d5173d05b7097755@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Jan 12, 2021, Paolo Bonzini wrote: > On 12/01/21 00:01, Sean Christopherson wrote: > > > Perhaps cpuid_query_maxphyaddr() should just look at the low 5 bits of > > > CPUID.80000008H:EAX? > > The low 6 bits I guess---yes, that would make sense and it would have also > fixed the bug. No, that wouldn't have fixed this specific bug. In this case, the issue was CPUID.80000008H:AL == 0; masking off bits 7:6 wouldn't have changed anything. And, masking bits 7:6 is architecturally wrong. Both the SDM and APM state that bits 7:0 contain the number of PA bits. KVM could reject guest.MAXPA > host.MAXPA, but arbitrarily dropping bits would be wrong.