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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 24E81C433DF for ; Tue, 26 May 2020 16:20:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBF34207D8 for ; Tue, 26 May 2020 16:20:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="lOvf70PK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388663AbgEZQUf (ORCPT ); Tue, 26 May 2020 12:20:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726282AbgEZQUe (ORCPT ); Tue, 26 May 2020 12:20:34 -0400 Received: from mail-pj1-x1043.google.com (mail-pj1-x1043.google.com [IPv6:2607:f8b0:4864:20::1043]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8CA46C03E96E for ; Tue, 26 May 2020 09:20:33 -0700 (PDT) Received: by mail-pj1-x1043.google.com with SMTP id ci23so36334pjb.5 for ; Tue, 26 May 2020 09:20:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=tLFWEc70kSJC3xDiyEWNVnyhuZzVWGIzcJ1Nk8rcOc0=; b=lOvf70PKmmBPmGfNSvXTYx9cNld/SJ4GdwXQvxyEWWWH1t24w5+WMVVyi9NbSTFCuo UK25Jfcc2kwV14PFFGZMUXnXGG/ZHoFAzR8a9RxeKmOFXG09X+v7nlHd/ZSRWUHPzodk QJfCvytXjqlRnpksslKFGoPUsAsLRdnDs5BS4= 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=tLFWEc70kSJC3xDiyEWNVnyhuZzVWGIzcJ1Nk8rcOc0=; b=n/TgTFhRDqw39yxgvFmcQ2hWY/xIdFQRgNzYwE+6z5y7J1puLlTELuozxZBFyQj6lj 4gzIGf4umI+84DvFATSVcPKCmNXojj99HMzL3Af380KN9KmWJkZ7ywR/PpNm5sPoV9u5 pxpiduX8mMLUty+Bb8/nBuyBIcGnrC48AcADUAIQa+4zY65Bd7WI+Dm9z7EpqWvqk+9B gd5K234Cq4ivcOs3EXLFONtBBgzZt0cSsHZ59Aek5TSohLE52HLJ4+XXh4hvDiMoPLJf S1xuizN+zG+wbYKALGhzb3scOMcekmMxWq/qdpNTCG6iZvmXaxktPLjm71CY4b48y4dP gcOw== X-Gm-Message-State: AOAM532BEaPJluy4rcz6RZKWRf/5Z+17HhkAm81ZVLixROCM2IuTH0pK Q6NWqO2XuK7MxT8tfamVVcLynw== X-Google-Smtp-Source: ABdhPJxEYTpmqGrCSWR6f1rzHdEg5LhA1BVPPbzcg+Vydop3DHCm/xEy4uzlTCOqImNwTjC3mqZ4Rg== X-Received: by 2002:a17:90a:fb96:: with SMTP id cp22mr27442990pjb.201.1590510033184; Tue, 26 May 2020 09:20:33 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id b63sm46799pfg.86.2020.05.26.09.20.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2020 09:20:32 -0700 (PDT) Date: Tue, 26 May 2020 09:20:31 -0700 From: Kees Cook To: Andi Kleen Cc: Greg KH , Andi Kleen , x86@kernel.org, linux-kernel@vger.kernel.org, sashal@kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v1] x86: Pin cr4 FSGSBASE Message-ID: <202005260918.72DE289@keescook> References: <20200526052848.605423-1-andi@firstfloor.org> <20200526065618.GC2580410@kroah.com> <20200526154835.GW499505@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200526154835.GW499505@tassilo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 26, 2020 at 08:48:35AM -0700, Andi Kleen wrote: > On Tue, May 26, 2020 at 08:56:18AM +0200, Greg KH wrote: > > On Mon, May 25, 2020 at 10:28:48PM -0700, Andi Kleen wrote: > > > + if (val & X86_CR4_FSGSBASE) { > > > + WARN_ONCE(1, "CR4 unexpectedly set FSGSBASE!?\n"); > > > > What about those systems that panic-on-warn? > > I assume they're ok with "panic on root hole" Exactly. :) The pinning infrastructure is pretty small; will that just get backported? (Also, we can probably rework the pinning to avoid the special-casing and use a mask/value pair to notice a bit getting turned _on_ as well...) -- Kees Cook