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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 73CB6C6778D for ; Tue, 11 Sep 2018 15:25:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 363B020645 for ; Tue, 11 Sep 2018 15:25:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 363B020645 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1727679AbeIKUZX (ORCPT ); Tue, 11 Sep 2018 16:25:23 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:33392 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726800AbeIKUZW (ORCPT ); Tue, 11 Sep 2018 16:25:22 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0EB1281A8073; Tue, 11 Sep 2018 15:25:35 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.34.27.30]) by smtp.corp.redhat.com (Postfix) with SMTP id 327B32156889; Tue, 11 Sep 2018 15:25:32 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 11 Sep 2018 17:25:34 +0200 (CEST) Date: Tue, 11 Sep 2018 17:25:31 +0200 From: Oleg Nesterov To: Kees Cook Cc: Rik van Riel , Michal Hocko , Stanislav Kozina , LKML Subject: Re: get_arg_page() && ptr_size accounting Message-ID: <20180911152531.GA9450@redhat.com> References: <20180910122907.GA23963@redhat.com> <20180910172109.GB27005@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Tue, 11 Sep 2018 15:25:35 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.8]); Tue, 11 Sep 2018 15:25:35 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'oleg@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/10, Kees Cook wrote: > > On Mon, Sep 10, 2018 at 10:21 AM, Oleg Nesterov wrote: > > > Could you explain what this patch actually prevents from? Especially > > now that we have stack_guard_gap? > > One of the many Stack Clash abuses was that it was possible to jump > over the stack gap with outrageous environment variables that got > expanded in stupid ways by, IIRC, glibc or the dynamic linker. The > point here was to be defensive in the face of future weaknesses, and > try to be robust in the face of crazy execs but workable under normal > (but large) execs. IOW, unlimited arg size makes many interesting attacks possible. This is clear, I was confused because I thought this patch fixes some particular problem not explained in the changelog. Thanks, Oleg.