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=-5.1 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,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 B3097C43603 for ; Sun, 8 Dec 2019 17:19:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8A70B20409 for ; Sun, 8 Dec 2019 17:19:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="oXnxX3E0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726665AbfLHRTX (ORCPT ); Sun, 8 Dec 2019 12:19:23 -0500 Received: from mail-wr1-f67.google.com ([209.85.221.67]:35115 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726472AbfLHRTX (ORCPT ); Sun, 8 Dec 2019 12:19:23 -0500 Received: by mail-wr1-f67.google.com with SMTP id g17so13418850wro.2; Sun, 08 Dec 2019 09:19:22 -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:mime-version:content-disposition :user-agent; bh=hJ551783o9ImIc/f28xz8rKXrHYxNx70TgHA3JxmnaY=; b=oXnxX3E0AsCAjLUi4ymzC7mQnsVvvUvM1731+3HdPdZL6kakMAdK8IyWnTBGfbIa0K cOumCj+euP80G+nRBykvoYFsRI/wtwDgI9gwkzMxyd93bEECKS1rt7gzkfEavMPOrSGN 0NHudKJCMgFU29ZHDk8HNn6yZa3RJocdsfjGbJWEAhvsIMMOL6cvVmRy8dCfav3BsxTI PFL1PW+CUBnvlRr41msShjHwRGZkYN+kasf7ow+y70HvuXaeyig79sEP9iQXE4e189Rr TvaW57XFYrZxGxnfaNfK/qckAE/I8ZwtHu5TDb33Teu0EjO2Zc605+xgHm8LhwPhvAOd ftzw== 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:mime-version :content-disposition:user-agent; bh=hJ551783o9ImIc/f28xz8rKXrHYxNx70TgHA3JxmnaY=; b=ZoKOsP0CVd93XG1qMD3EnU3vXgmOYM6UDY3wXZqj2SLF5QVcdXvqOZVRd2mWng41R4 v/hWVnsAPBz8Oxn1Qw57jniKTdFXqm7szZ0EKLsWzm9qedIJGNa5ghYcw0ma+iuIC019 ebhe22RfRdsCUl1KibadQw6iZd4uzORp9ArHdhLZ+ZlOXyIt0u7HnzakwzcsseVBfFk/ eCdG0QwqGnRHAdW0+u/QBrKHugG2XYnUFOQS2bQ3TIPO6HGRfFSzpfliWzv2ItjsKuff Zqvk1y8/Le+vTTcaeKcSnC9PS2APdCs5XtaujUsB+mjqx8lG26utjJrSL7gajsrIaaye wJaQ== X-Gm-Message-State: APjAAAUTu3Ip+HKA0FFBAtkoC6No5pKPYDa1u13yH7mjyFjRIKX+pxSH yXfTqdVZ2PSLUmMTVe0E9Q== X-Google-Smtp-Source: APXvYqztbmerjte0PZPdfwvWOIfvnFfr1Lgq24F0mQ2x9aUA7P5VI0zZPPNVfdk6YUoMtOXikoulOw== X-Received: by 2002:adf:8150:: with SMTP id 74mr27860550wrm.114.1575825561893; Sun, 08 Dec 2019 09:19:21 -0800 (PST) Received: from avx2 ([46.53.249.42]) by smtp.gmail.com with ESMTPSA id h2sm24387086wrv.66.2019.12.08.09.19.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Dec 2019 09:19:21 -0800 (PST) Date: Sun, 8 Dec 2019 20:19:18 +0300 From: Alexey Dobriyan To: akpm@linux-foundation.org Cc: dan.carpenter@oracle.com, will@kernel.org, ebiederm@xmission.com, linux-arch@vger.kernel.org, security@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] execve: warn if process starts with executable stack Message-ID: <20191208171918.GC19716@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline 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 over years: 1) linking innocent looking assembly file will silently add executable stack if proper linker options is not given as well: $ 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. Without doubt 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 many problems. Signed-off-by: Alexey Dobriyan --- v2: print pathname instead of comm/pid fs/exec.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/fs/exec.c +++ b/fs/exec.c @@ -761,6 +761,11 @@ int setup_arg_pages(struct linux_binprm *bprm, goto out_unlock; BUG_ON(prev != vma); + if (unlikely(vm_flags & VM_EXEC)) { + pr_warn_once("process '%pD4' started with executable stack\n", + bprm->file); + } + /* Move stack pages down in memory. */ if (stack_shift) { ret = shift_arg_pages(vma, stack_shift);