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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 66930C433FE for ; Wed, 9 Dec 2020 00:56:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E2EF238E2 for ; Wed, 9 Dec 2020 00:56:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726220AbgLIA4R (ORCPT ); Tue, 8 Dec 2020 19:56:17 -0500 Received: from 11.mo6.mail-out.ovh.net ([188.165.38.119]:44544 "EHLO 11.mo6.mail-out.ovh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725768AbgLIA4Q (ORCPT ); Tue, 8 Dec 2020 19:56:16 -0500 X-Greylist: delayed 9599 seconds by postgrey-1.27 at vger.kernel.org; Tue, 08 Dec 2020 19:56:15 EST Received: from player691.ha.ovh.net (unknown [10.108.35.90]) by mo6.mail-out.ovh.net (Postfix) with ESMTP id 0ED4A234E91 for ; Tue, 8 Dec 2020 22:51:48 +0100 (CET) Received: from sk2.org (82-65-25-201.subs.proxad.net [82.65.25.201]) (Authenticated sender: steve@sk2.org) by player691.ha.ovh.net (Postfix) with ESMTPSA id E733B190DB0A8; Tue, 8 Dec 2020 21:51:42 +0000 (UTC) Authentication-Results: garm.ovh; auth=pass (GARM-105G006f6ee3649-1f08-4f40-bb1f-df51397b003c, F7F8495E9FE719388847EB9DDB8A3A77E3CADC2E) smtp.auth=steve@sk2.org X-OVh-ClientIp: 82.65.25.201 From: Stephen Kitt To: linux-man@vger.kernel.org, Alejandro Colomar , Michael Kerrisk Cc: Christian Brauner , linux-kernel@vger.kernel.org, Stephen Kitt Subject: [patch] close_range.2: new page documenting close_range(2) Date: Tue, 8 Dec 2020 22:51:33 +0100 Message-Id: <20201208215133.30575-1-steve@sk2.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Ovh-Tracer-Id: 17686761638867717394 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedujedrudejiedgudehiecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemucehtddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpefhvffufffkofgggfestdekredtredttdenucfhrhhomhepufhtvghphhgvnhcumfhithhtuceoshhtvghvvgesshhkvddrohhrgheqnecuggftrfgrthhtvghrnhepteegudfgleekieekteeggeetveefueefteeugfduieeitdfhhedtfeefkedvfeefnecukfhppedtrddtrddtrddtpdekvddrieehrddvhedrvddtudenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhhouggvpehsmhhtphdqohhuthdphhgvlhhopehplhgrhigvrheiledurdhhrgdrohhvhhdrnhgvthdpihhnvghtpedtrddtrddtrddtpdhmrghilhhfrhhomhepshhtvghvvgesshhkvddrohhrghdprhgtphhtthhopehlihhnuhigqdhkvghrnhgvlhesvhhgvghrrdhkvghrnhgvlhdrohhrgh Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This documents close_range(2) based on information in 278a5fbaed89dacd04e9d052f4594ffd0e0585de and 60997c3d45d9a67daf01c56d805ae4fec37e0bd8. Signed-off-by: Stephen Kitt --- man2/close_range.2 | 112 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 112 insertions(+) create mode 100644 man2/close_range.2 diff --git a/man2/close_range.2 b/man2/close_range.2 new file mode 100644 index 000000000..62167d9b0 --- /dev/null +++ b/man2/close_range.2 @@ -0,0 +1,112 @@ +.\" Copyright (c) 2020 Stephen Kitt +.\" +.\" %%%LICENSE_START(VERBATIM) +.\" Permission is granted to make and distribute verbatim copies of this +.\" manual provided the copyright notice and this permission notice are +.\" preserved on all copies. +.\" +.\" Permission is granted to copy and distribute modified versions of this +.\" manual under the conditions for verbatim copying, provided that the +.\" entire resulting derived work is distributed under the terms of a +.\" permission notice identical to this one. +.\" +.\" Since the Linux kernel and libraries are constantly changing, this +.\" manual page may be incorrect or out-of-date. The author(s) assume no +.\" responsibility for errors or omissions, or for damages resulting from +.\" the use of the information contained herein. The author(s) may not +.\" have taken the same level of care in the production of this manual, +.\" which is licensed free of charge, as they might when working +.\" professionally. +.\" +.\" Formatted or processed versions of this manual, if unaccompanied by +.\" the source, must acknowledge the copyright and authors of this work. +.\" %%%LICENSE_END +.\" +.TH CLOSE_RANGE 2 2020-12-08 "Linux" "Linux Programmer's Manual" +.SH NAME +close_range \- close all file descriptors in a given range +.SH SYNOPSIS +.nf +.B #include +.PP +.BI "int close_range(int " first ", int " last ", unsigned int " flags ); +.fi +.SH DESCRIPTION +The +.BR close_range () +system call closes all open file descriptors from +.I first +to +.IR last +(included). +.PP +Errors closing a given file descriptor are currently ignored. +.PP +.I flags +can be set to +.B CLOSE_RANGE_UNSHARE +to unshare the range of file descriptors from any other processes, +.I instead +of closing them. +.SH RETURN VALUE +On success, +.BR close_range () +return 0. +On error, \-1 is returned and +.I errno +is set to indicate the cause of the error. +.SH ERRORS +.TP +.B EINVAL +.I flags +is not valid, or +.I first +is greater than +.IR last . +.TP +.B EMFILE +The per-process limit on the number of open file descriptors has been reached +(see the description of +.BR RLIMIT_NOFILE +in +.BR getrlimit (2)). +.TP +.B ENOMEM +Insufficient kernel memory was available. +.SH VERSIONS +.BR close_range () +first appeared in Linux 5.9. +.SH CONFORMING TO +.BR close_range () +is available on Linux and FreeBSD. +.SH NOTES +Currently, there is no glibc wrapper for this system call; call it using +.BR syscall (2). +.SH USE CASES +.\" 278a5fbaed89dacd04e9d052f4594ffd0e0585de +.\" 60997c3d45d9a67daf01c56d805ae4fec37e0bd8 +.SS Closing file descriptors before exec +File descriptors can be closed safely using +.PP +.in +4n +.EX +/* we don't want anything past stderr here */ +close_range(3, ~0U, CLOSE_RANGE_UNSHARE); +execve(....); +.EE +.in +.PP +.SS Closing all open file descriptors +This is commonly implemented (on Linux) by listing open file +descriptors in +.B /proc/self/fd/ +and calling +.BR close (2) +on each one. +.BR close_range () +can take care of this without requiring +.B /proc +and with a single system call, which provides significant performance +benefits. +.SH SEE ALSO +.BR close (2) base-commit: b5dae3959625f5ff378e9edf9139057d1c06bb55 -- 2.20.1