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References: <CAKfFMLQe3L3q_qJ-=07KiCQwraqQYP3jbB-8fohZaH9-7PWnSg AT mail DOT gmail DOT com>	<542902046 DOT 20140311163047 AT yandex DOT ru>
Date: Tue, 11 Mar 2014 08:40:34 -0400
Message-ID: <CAKfFMLR8RUR8x5pWt=+J5os+46Q9JQRMx3syWFJPVXxPj1HU4w@mail.gmail.com>
Subject: Re: File permissions when using ACLs
From: Charles Plager <cplager AT gmail DOT com>
To: cygwin AT cygwin DOT com
Content-Type: text/plain; charset=ISO-8859-1

Hi Andrey,

I understand that Cygwin is emulating POSIX permissions (and, yes, we
already turn this off using the /etc/fstab).  What I don't understand
is why it uses "special" permissions and not the standard "read/write"
options that are available.

One possibility I just though of: Cygwin uses special permissions in
the case where the file is not executable (but readable or
readable/writable)?  I guess I can see that.

I'd still love to hear from anybody who's experienced the vanishing
permissions...

Thanks!
  Charles

On Tue, Mar 11, 2014 at 8:30 AM, Andrey Repin <anrdaemon AT yandex DOT ru> wrote:
> Greetings, Charles Plager!
>
>> Short version: When writing to network drives (and probably local
>> ones) as Cygwin is setup by default, we see the permissions being set
>> using the ACLs where "creator owner"  is given "full control" and
>> "creator" group are given "read/execute", but by setting "special
>> permissions" instead of just having "full control" or "read/execute"
>> set.
>
>> Why does it not just set "full control" or "read/execute"?
>
> Cygwin by default mimicking POSIX permission set.
> If this behavior is undesirable, You can work around it by letting operating
> system control the ACL.
> Modify cygdrive entry in /etc/fstab to include noacl option.
> Then any files accessed outside direct/implied mounts will have permissions
> controlled by OS.
>
>> Long, slightly different version: When the above permissions get set,
>> we sometimes see (sometimes = 1 file in a million or less) a file that
>> ends up with no permissions.  Owner loses permissions, admin loses
>> permissions and so far, IT has only been able to make the file go away
>> by reformatting the drive.
>
>> When we tell Cygwin not to use ACLs (adding the following in
>> /etc/fstab), this does not seem to happen (in 100 million or so files
>> created).
>
>> none /cygdrive/ cygdrive binary,posix=0,user,noacl 0 0
>
>
>> This only seems to happen for files created by Cygwin with the ACL
>> permissions (although, to be fair, without Cygwin, I don't know that
>> anybody is generating as many files).  I'm assuming it isn't Cygwin,
>> per say, but rather something that interacts with how Cygwin setup the
>> permissions (and given the rarity of the problem it is difficult to
>> diagnose more thoroughly.
>
>> So, to sum up:
>
>> * Why use special permissions and not default settings when using ACLs?
>
>> * Anybody else experience  files that lose all permissions?  Any
>> suggestions on resetting the file (short of reformatting the drive)?
>
>> * Any other hints/insights that might be useful here?
>
>> Thanks,
>>   Charles
>
>> p.s.  We see this behavior for Cygwin 1.7.9 and beyond.  In 1.7.5, it
>> doesn't appear as if the ACLs are used and it acts as if "noacl" is
>> set.
>
>
> --
> WBR,
> Andrey Repin (anrdaemon AT yandex DOT ru) 11.03.2014, <16:08>
>
> Sorry for my terrible english...
>

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