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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7E47FC77B60 for ; Thu, 30 Mar 2023 17:21:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232301AbjC3RV0 (ORCPT ); Thu, 30 Mar 2023 13:21:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52500 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232318AbjC3RVY (ORCPT ); Thu, 30 Mar 2023 13:21:24 -0400 Received: from mail-wm1-x334.google.com (mail-wm1-x334.google.com [IPv6:2a00:1450:4864:20::334]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33D656194 for ; Thu, 30 Mar 2023 10:21:22 -0700 (PDT) Received: by mail-wm1-x334.google.com with SMTP id j36-20020a05600c1c2400b003f04057c152so146336wms.5 for ; Thu, 30 Mar 2023 10:21:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1680196880; x=1682788880; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=fPmrkxP8lA6mm8xNGo07bPYOfkrPR6g3BToZ+bsCS3c=; b=m02NEY4m0MsQBHmg6HVo0I865xOXoUm7zYocyK4yplShm8R13zIPKMTcg/6BkSSSMr fktfULG3scExIKbDaDY118Sm9xa2TiANG4qhpfeZ0r0enku70HrM9f4rFtgpy802m3J8 QKmHn1DFgr1TjxyhRkCmJ+kR7OG+EOd/KPIedzxH5wukU8KuVvGK9A5LJgFkmJDXiP5B eSxNtYAffbXX/+WLi7gH9Cqy3bf8n2dodfIF+tw2ohDZXbsLjNJHdEUlhdufczUWuRO+ eLGHwHp51DtACs7gBHJ1XdnUQid9FyRknaeAO1G7gysTk/xzErj8G5lzYqO+y2HM9dRr uvpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680196880; x=1682788880; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=fPmrkxP8lA6mm8xNGo07bPYOfkrPR6g3BToZ+bsCS3c=; b=BBGwqN9+ffnh5Pxg09WuHyffDD3OP/ZWq8t6XZwrF9VcZI20lc+sCJ2eltmqW2rwa7 DW0wZ3sU4VZvEZRrNvSxFj/aZ2fT0JM3o86ziWK+XKP+AorPA5mQQXnztnZM/7gtIfnO iEec9QmWyRFj7L5+b3Oju+D03bZpbv6jJg88q58eZKZLTYgTgdS84AF84In0UaQd1NKd X91hqGDff9mCqvWdQrnJr21ODaeH9OZUppgbDdZ+PbIhVgkrlKBlOR7gcwbwwRBA3pDh F3WobExCW241qZ8cQQHmTgyoXdggeYwV+lmMzU4M7xDpqBTA01GkVL5dSXDJVJygkOFY U/oQ== X-Gm-Message-State: AO0yUKXWCb4OZUehGSsamCFgTv4t99+pLYcz0II5G66UIF38OwuDOw64 tovWJ04mUlxGUFhapbenR3DuqoLLZSU= X-Google-Smtp-Source: AK7set/LoFCPP6hxq7r0EarZskBt24yWXwiE2OSQy9Pm50xlhelnA6s2EadV7BvR8tUsQhYHtccBEQ== X-Received: by 2002:a7b:ca4a:0:b0:3ee:555:ea60 with SMTP id m10-20020a7bca4a000000b003ee0555ea60mr20698202wml.8.1680196880497; Thu, 30 Mar 2023 10:21:20 -0700 (PDT) Received: from asus5775.alejandro-colomar.es ([170.253.51.134]) by smtp.googlemail.com with ESMTPSA id j19-20020a05600c191300b003ee1acdaf95sm6976067wmq.36.2023.03.30.10.21.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Mar 2023 10:21:20 -0700 (PDT) From: Alejandro Colomar X-Google-Original-From: Alejandro Colomar To: linux-man@vger.kernel.org Cc: Alejandro Colomar , =?UTF-8?q?Bastien=20Roucari=C3=A8s?= , glibc , GCC , Eric Blake , Stefan Puiu , Igor Sysoev , Rich Felker , Andrew Clayton , Richard Biener , Zack Weinberg , Florian Weimer , Joseph Myers , Jakub Jelinek , Sam James Subject: [PATCH] sockaddr.3type: Document that sockaddr_storage is the API to be used Date: Thu, 30 Mar 2023 19:13:11 +0200 Message-Id: <20230330171310.12330-1-alx@kernel.org> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org POSIX.1 Issue 8 will fix the long-standing issue with sockaddr APIs, which inevitably caused UB either on user code, libc, or more likely, both. sockaddr_storage has been clarified to be implemented in a manner that aliasing it is safe (suggesting a unnamed union, or other compiler magic). Link: Reported-by: Bastien Roucariès Reported-by: Alejandro Colomar Cc: glibc Cc: GCC Cc: Eric Blake Cc: Stefan Puiu Cc: Igor Sysoev Cc: Rich Felker Cc: Andrew Clayton Cc: Richard Biener Cc: Zack Weinberg Cc: Florian Weimer Cc: Joseph Myers Cc: Jakub Jelinek Cc: Sam James Signed-off-by: Alejandro Colomar --- Hi all, This is my proposal for documenting the POSIX decission of fixing the definition of sockaddr_storage. Bastien, I believe you had something similar in mind; please review. Eric, thanks again for the fix! Could you please also have a look at this? Cheers, Alex man3type/sockaddr.3type | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/man3type/sockaddr.3type b/man3type/sockaddr.3type index 32c3c5bd0..d1db87d5d 100644 --- a/man3type/sockaddr.3type +++ b/man3type/sockaddr.3type @@ -23,6 +23,14 @@ .SH SYNOPSIS .PP .B struct sockaddr_storage { .BR " sa_family_t ss_family;" " /* Address family */" +.PP +.RS 4 +/* This structure is not really implemented this way. It may be +\& implemented with an unnamed union or some compiler magic to +\& avoid breaking aliasing rules when accessed as any other of the +\& sockaddr_* structures documented in this page. See CAVEATS. +\& */ +.RE .B }; .PP .BR typedef " /* ... */ " socklen_t; @@ -122,6 +130,20 @@ .SH NOTES .I and .IR . +.SH CAVEATS +To avoid breaking aliasing rules, +programs that use functions that receive pointers to +.I sockaddr +structures should declare objects of type +.IR sockaddr_storage , +which is defined in a way that it +can be accessed as any of the different structures defined in this page. +Failure to do so may result in Undefined Behavior. +.PP +New functions should be written to accept pointers to +.I sockaddr_storage +instead of the traditional +.IR sockaddr . .SH SEE ALSO .BR accept (2), .BR bind (2), -- 2.39.2