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=-1.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 25FA9ECDE46 for ; Wed, 24 Oct 2018 18:49:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F342207DD for ; Wed, 24 Oct 2018 18:49:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ug1qJ8pc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9F342207DD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727372AbeJYDSm (ORCPT ); Wed, 24 Oct 2018 23:18:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:43826 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726521AbeJYDSm (ORCPT ); Wed, 24 Oct 2018 23:18:42 -0400 Received: from mail-wr1-f48.google.com (mail-wr1-f48.google.com [209.85.221.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 48C1220834 for ; Wed, 24 Oct 2018 18:49:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1540406970; bh=hAuW7PyzUjF6oeJUMXoQTxwgkTPb65VriMP9+LVfVaI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=Ug1qJ8pc+pkonafgVMDCmqiXobVkrIbU9ZGJITjgcETjxlFl7KtYqTHJsnSxHb42+ kAHidGAaca5wrFFFZs4u3XGfd4oEVGxFkTOZ+lKfJkWfwUGC7c4xxBRWMpc/ihsy+o MCIAgks3FRuS4fd+WalwMHARjYcGooRao/wC4Hhs= Received: by mail-wr1-f48.google.com with SMTP id l6-v6so6730145wrt.1 for ; Wed, 24 Oct 2018 11:49:30 -0700 (PDT) X-Gm-Message-State: AGRZ1gLIeN9ME8+AsLAwTPN9yz9dKPTE48KJ90yBj86flMJ4B2XfoDk7 Xm5HhPEUuXFzIo7lp1yt38o1kC64n4S0arj84Lhn9w== X-Google-Smtp-Source: AJdET5eolcOlngciFEFNPXmwM9p6gLPYnWz2/QCY66YBaoXFzHxcjUVxtcnWAMM+IQJF6J/Km4UB4mOH+ffoKYD23oc= X-Received: by 2002:a5d:4406:: with SMTP id z6-v6mr979744wrq.308.1540406968712; Wed, 24 Oct 2018 11:49:28 -0700 (PDT) MIME-Version: 1.0 References: <20181023163157.41441-1-kirill.shutemov@linux.intel.com> <20181023163157.41441-3-kirill.shutemov@linux.intel.com> In-Reply-To: <20181023163157.41441-3-kirill.shutemov@linux.intel.com> From: Andy Lutomirski Date: Wed, 24 Oct 2018 11:49:17 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/2] x86/ldt: Unmap PTEs for the slow before freeing LDT To: "Kirill A. Shutemov" Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Dave Hansen , Andrew Lutomirski , Peter Zijlstra , X86 ML , Linux-MM , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 23, 2018 at 9:32 AM Kirill A. Shutemov wrote: > > modify_ldt(2) leaves old LDT mapped after we switch over to the new one. > Memory for the old LDT gets freed and the pages can be re-used. > > Leaving the mapping in place can have security implications. The mapping > is present in userspace copy of page tables and Meltdown-like attack can > read these freed and possibly reused pages. Code looks okay. But: > - /* > - * Did we already have the top level entry allocated? We can't > - * use pgd_none() for this because it doens't do anything on > - * 4-level page table kernels. > - */ > - pgd = pgd_offset(mm, LDT_BASE_ADDR); This looks like an unrelated cleanup. Can it be its own patch?