From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752563AbbK1W7H (ORCPT ); Sat, 28 Nov 2015 17:59:07 -0500 Received: from a.ns.miles-group.at ([95.130.255.143]:11949 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751723AbbK1W7F (ORCPT ); Sat, 28 Nov 2015 17:59:05 -0500 Subject: Re: [PATCH 2/2] um: Use race-free temporary file creation To: =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= , linux-kernel@vger.kernel.org References: <1448746350-19998-1-git-send-email-mic@digikod.net> <1448746350-19998-3-git-send-email-mic@digikod.net> <565A258D.4040206@nod.at> <565A3128.8010605@digikod.net> Cc: Jeff Dike , Tristan Schmelcher , Greg Kroah-Hartman , user-mode-linux-devel@lists.sourceforge.net, user-mode-linux-user@lists.sourceforge.net, Al Viro From: Richard Weinberger Message-ID: <565A31B6.5050802@nod.at> Date: Sat, 28 Nov 2015 23:59:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <565A3128.8010605@digikod.net> Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 28.11.2015 um 23:56 schrieb Mickaël Salaün: > > On 28/11/2015 23:07, Richard Weinberger wrote: >> Am 28.11.2015 um 22:32 schrieb Mickaël Salaün: >>> Open the memory mapped file with the O_TMPFILE flag when available. >>> >>> Signed-off-by: Mickaël Salaün >>> --- >>> arch/um/os-Linux/mem.c | 12 ++++++++++++ >>> 1 file changed, 12 insertions(+) >>> >>> diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c >>> index 798aeb4..fe52e2d 100644 >>> --- a/arch/um/os-Linux/mem.c >>> +++ b/arch/um/os-Linux/mem.c >>> @@ -106,6 +106,18 @@ static int __init make_tempfile(const char *template) >>> } >>> } >>> >>> +#ifdef O_TMPFILE >>> + fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700); >>> + /* >>> + * If the running system does not support O_TMPFILE flag then retry >>> + * without it. >>> + */ >>> + if (fd != -1 || (errno != EINVAL && errno != EISDIR && >> >> Why are you handling EISDIR? > > I follow the man page for open [1], I think it was a workaround needed for some kernel versions just after the O_TMPFILE was added but before the support for EOPNOTSUPP. > We may need to add the EACCES too for some version of glibc [2, 3]? Makes sense! :) > 1. http://man7.org/linux/man-pages/man2/openat.2.html#BUGS > 2. Commit 69a91c237ab0ebe4e9fdeaf6d0090c85275594ec and https://sourceware.org/bugzilla/show_bug.cgi?id=17523 > 3. https://bugs.gentoo.org/529044 > >> >>> + errno != EOPNOTSUPP)) >>> + return fd; >>> + errno = 0; >> >> Why are you resetting errno? > > It's to ignore/reset the error code from open, but it may not be needed because of the next call to malloc? But then you'd have to reset errno after every syscall. :-) Thanks, //richard