X-Recipient:	archive-cygwin AT delorie DOT com
X-Spam-Check-By:	sourceware.org
Date:	Tue, 22 Mar 2011 19:01:09 +0100
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: O_ACCMODE is wrong
Message-ID:	<20110322180109.GH31220@calimero.vinschen.de>
Reply-To:	cygwin AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
References:	<4D88DF18 DOT 8050401 AT redhat DOT com>
MIME-Version:	1.0
In-Reply-To:	<4D88DF18.8050401@redhat.com>
User-Agent:	Mutt/1.5.21 (2010-09-15)
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Unsubscribe:	<mailto:cygwin-unsubscribe-archive-cygwin=delorie DOT com AT cygwin DOT com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com

On Mar 22 11:40, Eric Blake wrote:
> First, some background: POSIX 2008 introduced O_SEARCH and O_EXEC, and
> states that they may (but not must) share the same bit, since the former
> is for directories and the latter for non-directories (cygwin shares
> these as 0x400000).  POSIX states that implementations need not reject
> O_EXEC|O_RDONLY (to cater to systems like cygwin where O_RDONLY is 0),
> but that they may on systems where it is detectable (such as on Hurd
> where O_RDONLY is 1).  It also requires that an application must provide
> exactly one of the five modes O_RDONLY, O_WRONLY, O_RDWR, O_SEARCH, or
> O_EXEC), and therefore an implementation should reject a bit-wise or
> that tries to mix those modes).
> 
> However, in introducing the new values, POSIX also required that
> O_ACCMODE be updated to cover those new modes.
> 
> Now for the bugs: cygwin's <fcntl.h> defines O_ACCMODE as 3 instead of
> 0x400003, and as a result, a regular file opened for O_EXEC (or a
> directory for O_SEARCH) but probed via fcntl(F_GETFL)&O_ACCMODE will
> mistakenly show up as O_RDONLY instead of the proper mode.  Meanwhile,
> open(O_EXEC|O_WRONLY) isn't rejected as an invalid mode.  However, just
> changing O_ACCMODE to the correct value may expose other latent bugs in
> the rest of cygwin1.dll, since it looks like there are existing places
> where cygwin is making assumptions that rely on O_ACCMODE being exactly
> 3, so it would require a careful audit to fix it all.

Given that O_EXEC and O_SEARCH are not used anywhere in Cygwin it's not
exactly a pressing issue.  If you want to add the correct handling, feel
free to send a patch.


Corinna


P.S.: In theory this is better suited for the cygwin-developers list...


-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

- Raw text -