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Date: Fri, 08 Jan 2010 11:50:51 -0500
From: Raman Gupta <rocketraman AT fastmail DOT fm>
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To: cygwin AT cygwin DOT com
Subject: Re: 1.7.1-1 noacl on samba share has incorrect directory write bit
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On 01/08/2010 05:32 AM, Corinna Vinschen wrote:
> On Jan  7 15:25, Raman Gupta wrote:
>> On 01/07/2010 03:09 PM, Corinna Vinschen wrote:
>>> I'm talking about the other case.  The DOS R/O flag has nothing to do
>>> with writability of a directory in the first place.  If we treat a
>>> directory as non-writable just because the DOS R/O flag is set, we're
>>> making a mistake with consequences.  The consequences in the opposite
>>> case are much less problematic.
>>
>> Right -- which is why I suggested gating this using a "dro/nodro"
>> attribute so that it could be turned on by users of noacl samba
>> mounts where it would be correct to turn it on -- I suspect noacl
>> samba mounts are widely used and would benefit greatly from this as
>> EACCES would be correctly returned in many situations in which it
>> currently isn't.
>
> Show me an example.  The actual permissions are so that your actions
> already return EACCES.  I don't see lots of a win which would rectify
> another mount option.

Here is a simple foundational example -- assume "foo" is a 
non-writable directory on an smbfs share mounted with noacl, using the 
default samba share options:

$ if [[ -w foo ]]; then echo "writable"; else echo "not writable"; fi;
writable

which is of course incorrect as the directory is not actually writable:

$ touch foo/bar
touch: cannot touch `foo/bar': Permission denied

Another example is copying (with perms) from a noacl mount to an acl 
mount. The permissions of directories copied to the acl mount should 
be non-writable (and would be with the dro option) but currently the 
permissions on the acl mount are incorrectly set as writable:

Assume the following mounts:

//s/a on /mnt/acl type smbfs (binary,notexec,user)
//s/a on /mnt/noacl type smbfs (binary,notexec,noacl,user)
C:/cygwin on / type ntfs (binary,auto)

Share "a", again using the default samba options, contains a 
non-writable directory called "foo":

Now run:

$ mkdir /tmp/from_acl; mkdir /tmp/from_noacl

$ unison -auto -batch /mnt/acl /tmp/from_acl
[...]

$ unison -auto -batch /mnt/noacl /tmp/from_noacl
[...]

$ ls -l /tmp/from_acl
total 0
dr-x------+ 1 Raman Gupta None 0 2010-01-08 11:36 foo

$ ls -l /tmp/from_noacl
total 0
drwx------+ 1 Raman Gupta None 0 2010-01-08 11:36 foo

With the dro option, the latter would correctly remove the write bit 
on foo in /tmp/from_noacl.

Cheers,
Raman

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