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 D8AE4C11D3D for ; Thu, 27 Feb 2020 16:02:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC4A92469C for ; Thu, 27 Feb 2020 16:02:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="Qsxn4Hk1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729609AbgB0QCm (ORCPT ); Thu, 27 Feb 2020 11:02:42 -0500 Received: from mail-pl1-f193.google.com ([209.85.214.193]:41142 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729153AbgB0QCm (ORCPT ); Thu, 27 Feb 2020 11:02:42 -0500 Received: by mail-pl1-f193.google.com with SMTP id t14so1316037plr.8 for ; Thu, 27 Feb 2020 08:02:40 -0800 (PST) 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=9WYvJWXMZ+rcEfofeSJpHlDz/l6UP/pgxaBPI0bVL+I=; b=Qsxn4Hk1uahykr+QWbXHItx2AejCBY1osUAbIGB78L1sCo7B6Il4l6DND0mh7bGD0P VEphLT6LKCT7GeIYw8JhWS4IdRBHN9OjLD6OTWcRutDRZdUgwuaqV/hwpz3zxaBidUgO ggRjZ0IGbj3DcO3j9UNLtGA9Bagw1dMPj4wqU= 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=9WYvJWXMZ+rcEfofeSJpHlDz/l6UP/pgxaBPI0bVL+I=; b=LslSGSHdpyydQ1EtqJh6TYL7HhL98mQtD9yGeSZFzl9AsPQWpqRsVj6ycwso1HMBeu NHD6ZHgJZU0S0EgDgNN1R0ueVhJdiwnspH7/Rjdj/EKBIRMfr+AeouKaPKy8QGTnyj3n 80ems3oj91BZI/kDlNkLN6j9czSnv6xf8N1lWh7o91Bo4LCqMiHExK1NoGNqNt9hr8t/ tGY+UqQTlaGYEjJepTUSWPrnGVFjTAbHcGWNi5VhxQTYQVnRdOSN4w2zHt8G2W9EWvHo ama6ljrR7zRLR7pC05rCEgYvjlUfdYkhGFhyKYZHJeMttMkZRpLZfVBcbFztcxKPcUl5 MYYw== X-Gm-Message-State: APjAAAWFKaH4Hjgv5fdeGhhT4OuvnDx3xJBFOvYZtkklURooyO68nQxq U3THs7GHpmCOEx0OgAVzBJdqWw== X-Google-Smtp-Source: APXvYqwuoISNzfA3MpWinuXHZq6onkj6FotCRgoAwXWcPcaWOvayXN9eZRYUoFiSP4YFJQB9lCtKzA== X-Received: by 2002:a17:902:265:: with SMTP id 92mr402833plc.292.1582819359541; Thu, 27 Feb 2020 08:02:39 -0800 (PST) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id 5sm7682612pfx.163.2020.02.27.08.02.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Feb 2020 08:02:38 -0800 (PST) Date: Thu, 27 Feb 2020 08:02:37 -0800 From: Kees Cook To: Baoquan He 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: <202002270802.1CA8B32AC@keescook> References: <20200205223950.1212394-1-kristen@linux.intel.com> <20200205223950.1212394-10-kristen@linux.intel.com> <202002060428.08B14F1@keescook> <20200227024253.GA5707@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200227024253.GA5707@MiWiFi-R3L-srv> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Kees Cook