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,URIBL_BLOCKED,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 CAB82C4321E for ; Mon, 10 Sep 2018 17:44:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 92C062086A for ; Mon, 10 Sep 2018 17:44:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 92C062086A 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 S1728369AbeIJWjK (ORCPT ); Mon, 10 Sep 2018 18:39:10 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:38770 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726657AbeIJWjK (ORCPT ); Mon, 10 Sep 2018 18:39:10 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5A4E9DFF3; Mon, 10 Sep 2018 17:43:58 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.34.27.30]) by smtp.corp.redhat.com (Postfix) with SMTP id 99C751049499; Mon, 10 Sep 2018 17:43:55 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 10 Sep 2018 19:43:58 +0200 (CEST) Date: Mon, 10 Sep 2018 19:43:55 +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: <20180910174355.GA27312@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: <20180910172109.GB27005@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 10 Sep 2018 17:43:58 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 10 Sep 2018 17:43:58 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.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, Oleg Nesterov wrote: > > On 09/10, Kees Cook wrote: > > > > On Mon, Sep 10, 2018 at 9:41 AM, Kees Cook wrote: > > > On Mon, Sep 10, 2018 at 5:29 AM, Oleg Nesterov wrote: > > >> Hi Kees, > > >> > > >> I was thinking about backporting the commit 98da7d08850fb8bde > > >> ("fs/exec.c: account for argv/envp pointers"), but I am not sure > > >> I understand it... > > > > BTW, if you backport that, please get the rest associated with the > > various Stack Clash related weaknesses: > > may be... > > > da029c11e6b1 exec: Limit arg stack to at most 75% of _STK_LIM > > and I have to admit that I do not understand this patch at all, the > changelog explains nothing. > > Could you explain what this patch actually prevents from? Especially > now that we have stack_guard_gap? forgot to mention... with this patch #define MAX_ARG_STRINGS 0x7FFFFFFF doesn't match the reality. perhaps something like below makes sense just to make it clear, but this is cosmetic. Oleg. --- x/fs/exec.c +++ x/fs/exec.c @@ -1789,11 +1789,13 @@ static int __do_execve_file(int fd, stru if (retval) goto out_unmark; - bprm->argc = count(argv, MAX_ARG_STRINGS); + int max_arg_strings = _STK_LIM / 4 * 3 / 2; // actually even less than + + bprm->argc = count(argv, max_arg_strings); if ((retval = bprm->argc) < 0) goto out; - bprm->envc = count(envp, MAX_ARG_STRINGS); + bprm->envc = count(envp, max_arg_strings - bprm->argc); if ((retval = bprm->envc) < 0) goto out;