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Re: [PATCH] open: introduce O_NOSTD
From: |
Eric Blake |
Subject: |
Re: [PATCH] open: introduce O_NOSTD |
Date: |
Fri, 28 Aug 2009 07:04:40 -0600 |
User-agent: |
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.23) Gecko/20090812 Thunderbird/2.0.0.23 Mnenhy/0.7.6.666 |
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According to Florian Weimer on 8/28/2009 6:52 AM:
> * Eric Blake:
>
>> Your version fails to clear the cloexec bit of the final fd if the
>> original caller didn't request O_CLOEXEC.
>
> Okay, but you can fix that in a race-free manner (but I thought that
> this was implied by open_safer).
The current semantics of gnulib's open_safer is that the result is
guaranteed to be 3 or larger. It would require an audit of all gnulib
clients of the open_safer method to see whether it also makes sense to
change the semantics of open_safer to also guarantee that fds start life
with the cloexec bit set. But maybe that is a change worth making in
gnulib, with applications intending to give an fd to a child process being
required to explicitly clear the cloexec bit.
>> Also, your suggestion has a definite race in that you are calling
>> open() multiple times rather than cloning an existing fd after the
>> first open(), such that another process could alter which file is
>> visited between your first and last open().
>
> Sure, but this is an unobservable differen.ce
It is absolutely observable - if the user passed O_CREAT|O_EXCL as part of
their flags, then the second open() will inappropriately fail.
- --
Don't work too hard, make some time for fun as well!
Eric Blake address@hidden
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- [RFC] new open flag O_NOSTD, Eric Blake, 2009/08/24
- [PATCH] open: introduce O_NOSTD, Eric Blake, 2009/08/25
- Re: [PATCH] open: introduce O_NOSTD, Davide Libenzi, 2009/08/25
- Re: [PATCH] open: introduce O_NOSTD, Florian Weimer, 2009/08/27
- Re: [PATCH] open: introduce O_NOSTD, Eric Blake, 2009/08/28
- Re: [PATCH] open: introduce O_NOSTD, Florian Weimer, 2009/08/28
- Re: [PATCH] open: introduce O_NOSTD, Eric Blake, 2009/08/28
- Re: [PATCH] open: introduce O_NOSTD,
Eric Blake <=
- Re: [PATCH] open: introduce O_NOSTD, Davide Libenzi, 2009/08/27
- Re: [PATCH] open: introduce O_NOSTD, Ulrich Drepper, 2009/08/27
Re: [RFC] new open flag O_NOSTD, James Youngman, 2009/08/30