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=-5.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 ACBBCC432C0 for ; Mon, 18 Nov 2019 21:52:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83D59208CE for ; Mon, 18 Nov 2019 21:52:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="CJolYGs0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726911AbfKRVwc (ORCPT ); Mon, 18 Nov 2019 16:52:32 -0500 Received: from mail-wr1-f65.google.com ([209.85.221.65]:34305 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726647AbfKRVwc (ORCPT ); Mon, 18 Nov 2019 16:52:32 -0500 Received: by mail-wr1-f65.google.com with SMTP id e6so21397713wrw.1; Mon, 18 Nov 2019 13:52:30 -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=RFg17RVVONYlOMgS/v5AT5Q6B713XrluYPByCtEM3YQ=; b=CJolYGs0Qf/+JyoirAjBDN4t9ddPaPQC6l5G8NtNBjny2R7Iz14wqXq2DlwOpS2JbW /HzwMxzqHt6ojDsYc76Q/iq4UCW2un+aEyUAG8I25QG4kXt7+4fFGhZM2rMJDErZLxd/ njjqAJEkOtkJ9CFUdxlerEepkmhn/ZDoQEdSk0iNslRpeTWiPCsrjpcF5A9dlf7QxjtR DJHhWmyW6t/tQ7sLc8ywvBPZnl8h5C3CteEmGe2CzigvCN3no6KDYT1WUgzf1As0ZrVT 9CuKQJAzif0sJoY/GPQ/+t1z4rkSSUhyoGGpaTiqIh4+ZiK9sWxAjD5CRc+hUhrK2nzr AuWg== 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=RFg17RVVONYlOMgS/v5AT5Q6B713XrluYPByCtEM3YQ=; b=LMPR0dq2BIwr9GK9ZEXger5taMWvAuZ3tPJJLmUBdgiIyhtr3f4aBebvdlSNu6pe08 ad2SchLGeXZVZ+yJuqgk57fpghZzokPchy7XEziCvCkBH69EWccjxoOVFtOMRpZcZRvH aBBswovEHCVCX9pcx4QFijp4jxKC03drwN0GB1BdHH4KFUa1a6DxAU70X+zR1XO19rFy mHa0CDD7rdAfxhz4eGR0kr9w8N5xDGh4eDch6Y0ZLmP/0U5A2/9rhxQ8Wiydu9qz89LL W1iabgzCC6C0yF0CnJc3VbAqB/5cg/OEOSrIwh5Ncg9B72Jj8+NUA/lH7glRXQkCtGfI tZGw== X-Gm-Message-State: APjAAAUerd6h06gInZs/ganaY7zx5quJNjlbVd/uzYf1cXKYmBPflyLy yWWoPKpn02QL+HbVHcTirnYeXb8= X-Google-Smtp-Source: APXvYqz0HrUfdYTI5c1gDu9NFRnvGRkNfEQmND3aCFciylfs4FiKCe1Eg7A09WKxcCEs/scGoRkdSw== X-Received: by 2002:adf:ea8d:: with SMTP id s13mr33327276wrm.366.1574113949897; Mon, 18 Nov 2019 13:52:29 -0800 (PST) Received: from avx2 ([46.53.249.232]) by smtp.gmail.com with ESMTPSA id a2sm21058093wrt.79.2019.11.18.13.52.29 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 Nov 2019 13:52:29 -0800 (PST) Date: Tue, 19 Nov 2019 00:52:27 +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: [PATCH] exec: warn if process starts with executable stack Message-ID: <20191118215227.GA24536@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 There were few episodes of silent downgrade to an executable stack: 1) linking innocent looking assembly file $ cat f.S .intel_syntax noprefix .text .globl f f: ret $ cat main.c void f(void); int main(void) { f(); return 0; } $ gcc main.c f.S $ readelf -l ./a.out GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 RWE 0x10 2) converting C99 nested function into a closure https://nullprogram.com/blog/2019/11/15/ void intsort2(int *base, size_t nmemb, _Bool invert) { int cmp(const void *a, const void *b) { int r = *(int *)a - *(int *)b; return invert ? -r : r; } qsort(base, nmemb, sizeof(*base), cmp); } will silently require stack trampolines while non-closure version will not. While without a double this behaviour is documented somewhere, add a warning so that developers and users can at least notice. After so many years of x86_64 having proper executable stack support it should not cause too much problems. If the system is old or CPU is old, then there will be an early warning against init and/or support personnel will write that "uh-oh, our Enterprise Software absolutely requires executable stack" and close tickets and customers will nod heads and life moves on. Signed-off-by: Alexey Dobriyan --- fs/exec.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/fs/exec.c +++ b/fs/exec.c @@ -762,6 +762,11 @@ int setup_arg_pages(struct linux_binprm *bprm, goto out_unlock; BUG_ON(prev != vma); + if (vm_flags & VM_EXEC) { + pr_warn_once("process '%s'/%u started with executable stack\n", + current->comm, current->pid); + } + /* Move stack pages down in memory. */ if (stack_shift) { ret = shift_arg_pages(vma, stack_shift);