Re: Weird issue with file permissions

[Ken Brown <kbrown@cornell.edu>]

On 7/1/2022 11:23 PM, Lavrentiev, Anton (NIH/NLM/NCBI) [C] wrote:
>> That way I'm sure I won't have any surprises with permissions when working in
>> /cygdrive/g/cygwin.  Do you want to try that and see if it makes a difference?
> 
> I have no problems with /cygdrive/g/cygwin -- my socket file gets created there with proper
> permissions and reported so, too (both fstat and stat).

Right, I understood that.  But the (default) ACL on that directory influences 
the ACL on subdirectories that are created. And there's also interaction between 
the default ACL and the umask 
(https://man7.org/linux/man-pages/man2/umask.2.html).  So I think it couldn't 
hurt to try my suggestion and then see if you continue to see weird behavior on 
newly created subdirectories.

I just tried this myself on an external hard drive on which I've never touched 
the permissions on the top-level directory.  I do see some weirdness (though not 
as extreme as yours), and the weirdness goes away when I change the ACL as I 
suggested you do.  Here's what I see.  [Note: I use /mnt as the cygdrive prefix.]

$ pwd
/mnt/d

$ getfacl .
# file: .
# owner: Administrators
# group: Unknown+Group
user::---
group::rwx              #effective:---
group:SYSTEM:rwx        #effective:---
mask::---
other::rwx
default:user::rwx
default:group::---
default:group:SYSTEM:rwx        #effective:---
default:mask::---
default:other::rwx

$ mkdir cygwin

$ cd cygwin/

$ getfacl .
# file: .
# owner: kbrown
# group: None
user::rwx
group::r-x
group:SYSTEM:rwx        #effective:r-x
mask::r-x
other::r-x
default:user::rwx
default:group::r-x
default:group:SYSTEM:rwx        #effective:r-x
default:mask::r-x
default:other::rwx

$ ./sun
fstat mode = 140666
stat mode = 140646

$ ls -l .socket
srw-r--rw- 1 kbrown None 0 2022-07-02 09:47 .socket=

$ mkdir sub

$ cd sub

$ ../sun.exe
fstat mode = 140666
stat mode = 140646

$ ls -l .socket
srw-r--rw- 1 kbrown None 0 2022-07-02 09:49 .socket=

$ cd ..

$ getfacl ~ | setfacl -f - .

$ getfacl .
# file: .
# owner: kbrown
# group: None
user::rwx
group::r-x
other::r-x
default:user::rwx
default:group::r-x
default:other::r-x

$ mkdir sub1

$ cd sub1

$ ../sun.exe
fstat mode = 140666
stat mode = 140666

$ ll .socket
srw-rw-rw- 1 kbrown None 0 2022-07-02 10:04 .socket=

Note that stat and fstat disagreed at first but then agreed after I put a 
standard ACL on the cygwin directory.

Having said all that, I still want to look into why stat and fstat disagree.

Ken