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Date: Wed, 6 Oct 2010 13:21:33 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Cygwin >= 1.7.6 open message queues - permission denied
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On Oct  6 10:13, Manuel Wienand wrote:
> Hi,
> 
> I noticed that I get a permission denied error when I try to open a message queue in the same process or
> in an other process.
> The problem can be reproduced using the code given at: http://sourceware.org/ml/cygwin/2009-09/msg00629.html

Confirmed.  I'll investigate.

> Another thing I noticed is that the execute permission won't be set for the owner of the message queue file.
> E.g. in mq_open I set (S_IRWXU | S_IRWXG | S_IRWXO), but when looking at the created file in the cygwin shell
> (located in /dev/mqueue/) the permissions are set to "-rw-rwxrwx". But it doesn't seem to have any impact on
> the permission denied problem, since the execute permission isn't set in any of the tested versions.

The S_IXUSR bit has no meaning for message queues.  In Cygwin it's used
to signal that the message queue is still being initialized.  The
initializing process always creates the file with S_IXUSR bit.  When the
initalization has been finished, it removes the S_IXUSR bit.


Corinna

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

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