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=-2.4 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,USER_AGENT_SANE_1 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 08906C3F2CF for ; Fri, 28 Feb 2020 03:37:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D166424690 for ; Fri, 28 Feb 2020 03:37:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OJ7Z5xT8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730811AbgB1DhC (ORCPT ); Thu, 27 Feb 2020 22:37:02 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:57023 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730630AbgB1DhC (ORCPT ); Thu, 27 Feb 2020 22:37:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582861021; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=aDJjztBIb3g7WuQ8tm9j5jVgnbmxznk84OuAMLjRbBQ=; b=OJ7Z5xT8kgtMXRIZOYfxNCfKkLv5Sbffh+O4OLYmv7legVzzY5N4ziVV5LnbWBvrolKVyy iQN5whzpD2El2X9cbczqtxB8HH5QQaqFJW7XMYvPvf5Jxjr3sGJ9UVJiSNBy7bTniKEQPj gYQDXTqPmwi9dAwJg32mcbyYjD5dIjU= 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-1-RILYYk35OgShqd8ub0Y2sA-1; Thu, 27 Feb 2020 22:36:57 -0500 X-MC-Unique: RILYYk35OgShqd8ub0Y2sA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0C33B10509B8; Fri, 28 Feb 2020 03:36:55 +0000 (UTC) Received: from localhost (ovpn-12-49.pek2.redhat.com [10.72.12.49]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 36AE45D9CD; Fri, 28 Feb 2020 03:36:50 +0000 (UTC) Date: Fri, 28 Feb 2020 11:36:48 +0800 From: Baoquan He To: Kees Cook Cc: Kristen Carlson Accardi , dyoung@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, arjan@linux.intel.com, rick.p.edgecombe@intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, kexec@lists.infradead.org Subject: Re: [RFC PATCH 09/11] kallsyms: hide layout and expose seed Message-ID: <20200228033648.GJ24216@MiWiFi-R3L-srv> References: <20200205223950.1212394-1-kristen@linux.intel.com> <20200205223950.1212394-10-kristen@linux.intel.com> <202002060428.08B14F1@keescook> <20200227024253.GA5707@MiWiFi-R3L-srv> <202002270802.1CA8B32AC@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202002270802.1CA8B32AC@keescook> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/27/20 at 08:02am, Kees Cook wrote: > On Thu, Feb 27, 2020 at 10:42:53AM +0800, Baoquan He wrote: > > On 02/06/20 at 09:51am, Kristen Carlson Accardi wrote: > > > On Thu, 2020-02-06 at 04:32 -0800, Kees Cook wrote: > > > > > > In the past, making kallsyms entirely unreadable seemed to break > > > > weird > > > > stuff in userspace. How about having an alternative view that just > > > > contains a alphanumeric sort of the symbol names (and they will > > > > continue > > > > to have zeroed addresses for unprivileged users)? > > > > > > > > Or perhaps we wait to hear about this causing a problem, and deal > > > > with > > > > it then? :) > > > > > > > > > > Yeah - I don't know what people want here. Clearly, we can't leave > > > kallsyms the way it is. Removing it entirely is a pretty fast way to > > > figure out how people use it though :). > > > > Kexec-tools and makedumpfile are the users of /proc/kallsyms currently. > > We use kallsyms to get page_offset_base and _stext. > > AIUI, those run as root so they'd be able to consume the uncensored > output. Yes, they have to be run under root.