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=-2.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 84A5AC432C0 for ; Mon, 18 Nov 2019 21:36:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5371B22312 for ; Mon, 18 Nov 2019 21:36:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="LLKAsm3r" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726983AbfKRVgJ (ORCPT ); Mon, 18 Nov 2019 16:36:09 -0500 Received: from mail-wm1-f66.google.com ([209.85.128.66]:37818 "EHLO mail-wm1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726272AbfKRVgJ (ORCPT ); Mon, 18 Nov 2019 16:36:09 -0500 Received: by mail-wm1-f66.google.com with SMTP id b17so1005683wmj.2; Mon, 18 Nov 2019 13:36:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=3U41JlNG7bmxOGHw7h3r5PhFdgBWCIWUMpCYBIyDX5g=; b=LLKAsm3rpD9z4ttlmsVYBZB0RM5zgfviHGTvw9h3rNevt9PO2W7pC69F55PWExC5or xKTpurUY/Pe9PN5ERR9oct08+jkVImbmiNwqn5edtTzEzKVMVK0Ee4rgbQ5gB7XQQDZp Bp7k58/kfQJxRA4F5Bgesg/0CWjUs3kcM3Tw4AGJ0az2GnW15QEhg4C1izybBN6yMwxV nBBndV3fuZdkD9dyaRTaNMMQkEGx0HmT7eSZdd9SpJyc7NzL0pa1ExLbC0pcCXFhSBE2 IVwMB/NSYYQcjqDeyfmzKz5jIu9fL1mY63i0lfb8YPtVatTq9w9IJjpUnQFpH5+IPhRH F8SA== 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:user-agent; bh=3U41JlNG7bmxOGHw7h3r5PhFdgBWCIWUMpCYBIyDX5g=; b=OGhz694dunIhuDIwOB9V+lWKQEGU7/1dzbzsKhduRdoodN1B8UzO3lGofhHGBteQd6 F/85BJpjcKYNOFDK/T59kd4Rl/nvmvOeNlKLMx/idnCw2U8f3KNMauHQGqStsVozjK6X dR31i1fVfpXhMVPZUxgbB6W0uSTXTySqOpstBp6URU2QcPare+rojie9gDV1H3I7Ohq4 0blCuwjblU0Biw95MLFxRn4qU8wvj/NWNCaoc5EZzPMbbypjPzBeaIKHFm+qdX4XiVdE 5/lEIWMNc02714xTYrkKd30XdZ5RbZoPUOkgPM91hTsqb4fZ/MhRGWxs7Y4o/RlHh4rK dHhw== X-Gm-Message-State: APjAAAV+LfVzEpnQbixQSzNBzKwFg+98p/wy2oJoMh/Wge9FgsqXQ+TJ 4O8p/rv4Zn8GZTO5bl9TbVZB3Os= X-Google-Smtp-Source: APXvYqz+FxnF8eL6HtNJrp/JKyCLY4TQWIkK5/lzGWRZ4PSKc9jviQu0xhTt4sFmJ9MoTHBXKHPENg== X-Received: by 2002:a1c:9a4f:: with SMTP id c76mr1542479wme.103.1574112967007; Mon, 18 Nov 2019 13:36:07 -0800 (PST) Received: from avx2 ([46.53.249.232]) by smtp.gmail.com with ESMTPSA id u18sm25048020wrp.14.2019.11.18.13.36.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 Nov 2019 13:36:06 -0800 (PST) Date: Tue, 19 Nov 2019 00:36:03 +0300 From: Alexey Dobriyan To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, security@kernel.org, ben.dooks@codethink.co.uk Subject: Re: [PATCH] ELF: warn if process starts with executable stack Message-ID: <20191118213603.GA24086@avx2> References: <20191118145114.GA9228@avx2> <20191118125457.778e44dfd4740d24795484c7@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20191118125457.778e44dfd4740d24795484c7@linux-foundation.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 18, 2019 at 12:54:57PM -0800, Andrew Morton wrote: > On Mon, 18 Nov 2019 17:51:15 +0300 Alexey Dobriyan wrote: > > > PT_GNU_STACK is fail open design, > > Not sure what this means. Please expand on the motivation for this > change. > > > at least warn people that something > > isn't right. > > People who use an executable stack get a kernel splat. How is that > useful? There were two stories about silent downgrade to an executable stack: 1) compiling .S file and linking it to normal code: $ cat f.S .intel_syntax noprefix .text .globl f f: ret will silently add PT_GNU_STACK segment with RWE permissions 2) closures with nested functions will require executable stack https://nullprogram.com/blog/2019/11/15/ > > --- a/fs/exec.c > > +++ b/fs/exec.c > > @@ -762,6 +762,13 @@ int setup_arg_pages(struct linux_binprm *bprm, > > goto out_unlock; > > BUG_ON(prev != vma); > > > > +#ifdef CONFIG_MMU This code is already under CONFIG_MMU. I'll resend.