From: "H. Peter Anvin" <hpa@zytor.com>
To: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
akpm@linux-foundation.org, viro@zeniv.linux.org.uk,
drepper@gmail.com, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] nextfd(2)
Date: Wed, 11 Apr 2012 13:32:30 -0700 [thread overview]
Message-ID: <4F85EA5E.6070106@zytor.com> (raw)
In-Reply-To: <CAHGf_=pjksePXKsnfmxBC1BNgd_jDuy=-q9WMvM4UHjKi_fPaQ@mail.gmail.com>
On 04/11/2012 01:23 PM, KOSAKI Motohiro wrote:
>
> Hmmm.... I'm sorry I don't find "considered undesirable". Maybe because
> my English is not very good. can you please help me clarify?
>
I also went and read the mailing list discussion on the topic.
Ulrich, for example (in his usual mild-mannered style), commented:
> And all these programs and systems are wrong.
>
> There is no guarantee that one of the fds isn't used behind the
> scenes for something important which is still running as part of the
> fork/exec code. It's completely unacceptable to build into the
> interfaces the assumption that the programmer knows all the file
> descriptors.
>
> This is why using CLOEXEC is the only correct way to deal with this
> and now there is no exceuse anymore whatsoever. Every fd-creating
> interface can use CLOEXEC.
> This text says,
>
>> so a future revision of the standard may indeed add fdwalk( ), although no
>> one in the meeting was willing to draft a proposal for fdwalk( ) at this time
>
> and, later says after noting F_NEXT and O_CLOEXEC,
>
>> Therefore, the rest of this proposal seeks to document the problem
>> with closing arbitrary file descriptors, and a new bugid will be
>> opened to propose standardizing some recent interfaces and interface
>> extensions first appearing in Linux
>
> Do you think latter override former?
Yes.
>>>> b) unsafe because there might be file descriptors used by libc itself.
>>>
>>> I agree this. Even though almost developer don't use libc message catalogue and
>>> we can avoid such issue by using nextfd() + fcntl(O_CLOEXEC).
>>
>> No, that's exactly the point that we cannot.
>
> I thknk we are talking different aspect. I'm talking practical issue.
> say, ruby hit the exact same issue
> because valgrind uses internal fds and they don't think their exec()
> case don't need fd
> inheritance. Even though it close libc internal fds, invoked new
> executable may open them
> again at process strtup code. Therefore, they are using O_CLOEXEC. In
> the other hands,
> you seems talking about it is corner case. If so, I agree. I was not
> argue it. I only say, I
> haven't seen real world application require it.
>
> Personally, I'm only interesting real world issue.
These are real-world issues.
>> The problem -- as was brought up in the POSIX discussion -- is that you
>> actually end up breaking *properly functioning programs*.
>
> But the url only talk about a possibility of misuse.
There are concrete examples on the mailing list.
Anyway, fdwalk() at least exists as an interface. There is absolutely
no momentum for FD_NEXT that I can see.
-hpa
next prev parent reply other threads:[~2012-04-11 20:32 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-01 12:57 [PATCH] nextfd(2) Alexey Dobriyan
2012-04-01 13:58 ` Konstantin Khlebnikov
2012-04-01 21:30 ` Alexey Dobriyan
2012-04-02 0:09 ` Alan Cox
2012-04-02 8:38 ` Konstantin Khlebnikov
2012-04-02 9:26 ` Cyrill Gorcunov
2012-04-01 15:43 ` Eric Dumazet
2012-04-01 21:31 ` Alexey Dobriyan
2012-04-01 21:36 ` Alan Cox
2012-04-01 17:20 ` Linus Torvalds
2012-04-01 18:28 ` Valentin Nechayev
2012-04-01 21:33 ` Alexey Dobriyan
2012-04-01 19:21 ` Arnd Bergmann
2012-04-01 21:35 ` Alexey Dobriyan
2012-04-01 22:05 ` H. Peter Anvin
2012-04-04 12:13 ` Arnd Bergmann
2012-04-01 22:03 ` H. Peter Anvin
2012-04-01 22:13 ` H. Peter Anvin
2012-04-02 0:08 ` Alan Cox
2012-04-30 9:58 ` Valentin Nechayev
2012-04-02 1:19 ` Kyle Moffett
2012-04-02 1:37 ` H. Peter Anvin
2012-04-02 11:37 ` Ulrich Drepper
2012-04-06 9:54 ` Alexey Dobriyan
2012-04-06 15:27 ` Colin Walters
2012-04-06 16:14 ` H. Peter Anvin
2012-04-06 20:16 ` Alexey Dobriyan
2012-04-06 20:33 ` H. Peter Anvin
2012-04-06 21:02 ` H. Peter Anvin
2012-04-12 10:54 ` Alexey Dobriyan
2012-04-12 11:11 ` Alan Cox
2012-04-12 13:35 ` Alexey Dobriyan
2012-04-12 13:51 ` H. Peter Anvin
2012-04-12 19:21 ` Alexey Dobriyan
2012-04-12 14:09 ` Eric Dumazet
2012-04-06 16:23 ` H. Peter Anvin
2012-04-07 21:21 ` Ben Pfaff
2012-04-11 0:12 ` KOSAKI Motohiro
2012-04-11 0:09 ` KOSAKI Motohiro
2012-04-11 17:58 ` H. Peter Anvin
2012-04-11 18:04 ` Linus Torvalds
2012-04-11 18:11 ` H. Peter Anvin
2012-04-11 19:46 ` KOSAKI Motohiro
2012-04-11 19:49 ` H. Peter Anvin
2012-04-11 20:23 ` KOSAKI Motohiro
2012-04-11 20:32 ` H. Peter Anvin [this message]
2012-04-17 18:12 ` KOSAKI Motohiro
2012-04-11 18:00 ` H. Peter Anvin
2012-04-11 19:20 ` KOSAKI Motohiro
2012-04-11 19:22 ` H. Peter Anvin
2012-04-11 19:26 ` KOSAKI Motohiro
2012-04-11 19:28 ` H. Peter Anvin
2012-04-11 19:31 ` KOSAKI Motohiro
2012-04-11 19:32 ` H. Peter Anvin
2012-04-02 23:17 ` KOSAKI Motohiro
2012-04-02 23:56 ` H. Peter Anvin
2012-04-04 11:51 ` Ulrich Drepper
2012-04-04 16:38 ` KOSAKI Motohiro
2012-04-04 16:43 ` Ulrich Drepper
2012-04-04 17:07 ` KOSAKI Motohiro
2012-04-04 17:49 ` Ulrich Drepper
2012-04-04 18:08 ` KOSAKI Motohiro
2012-04-04 16:31 ` KOSAKI Motohiro
2012-04-04 17:10 ` Colin Walters
2012-04-04 17:25 ` Colin Walters
2012-04-04 23:35 ` KOSAKI Motohiro
2012-04-04 18:44 ` H. Peter Anvin
2012-04-03 19:21 ` Colin Walters
2012-04-04 3:01 ` Al Viro
2012-04-04 17:10 ` KOSAKI Motohiro
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