From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 124043 invoked by alias); 25 Jun 2018 06:21:24 -0000 Mailing-List: contact gnu-gabi-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Post: List-Help: List-Subscribe: Sender: gnu-gabi-owner@sourceware.org Received: (qmail 124030 invoked by uid 89); 25 Jun 2018 06:21:24 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Checked: by ClamAV 0.99.4 on sourceware.org X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.3 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,SPF_HELO_PASS autolearn=no version=3.3.2 spammy=older X-Spam-Status: No, score=-1.3 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,SPF_HELO_PASS autolearn=no version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on sourceware.org X-Spam-Level: X-HELO: mx1.redhat.com Received: from mx3-rdu2.redhat.com (HELO mx1.redhat.com) (66.187.233.73) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 25 Jun 2018 06:21:22 +0000 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 01E664001388; Mon, 25 Jun 2018 06:21:21 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-116-195.ams2.redhat.com [10.36.116.195]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 36A9C2027056; Mon, 25 Jun 2018 06:21:19 +0000 (UTC) Subject: Re: RFA: Add a new gynamic tag: DT_GNU_GOT_PLT_END To: Cary Coutant Cc: Nick Clifton , gnu-gabi@sourceware.org, "H.J. Lu" References: <87sh5hadd6.fsf@redhat.com> <83d583d0-884e-4208-436e-5b25cbb6ce5a@redhat.com> From: Florian Weimer Message-ID: Date: Mon, 01 Jan 2018 00:00:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Mon, 25 Jun 2018 06:21:21 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Mon, 25 Jun 2018 06:21:21 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'fweimer@redhat.com' RCPT:'' X-IsSubscribed: yes X-SW-Source: 2018-q2/txt/msg00012.txt.bz2 On 06/24/2018 11:05 PM, Cary Coutant wrote: >>> That leads me to another question: How would this be different from -z >>> relro -z now? It looks to me like a binary with such a PLT GOT would >>> be nothing more than a -z relro -z now binary where nothing but the >>> .got.plt section ends up as RELRO. So why not just use the >>> PT_GNU_RELRO program header for this? >> >> It doesn't disable lazy binding, so there is no visible semantic difference >> in symbol binding. >> >> With page isolation, we can use pkey_mprotect to assign a protection key to >> the .got.plt and only make it readable while _dl_fixup is running. That >> would provide most of the security benefits of BIND_NOW+RELRO, without >> disabling lazy binding. > > OK, so it's a variant of RELRO. I'd prefer using a new program header > type, PT_GNU_PLTGOT, then. Wouldn't this cause the binaries not to run with an older loader? Thanks, Florian