Re: Weird issue with file permissions

[Ken Brown <kbrown@cornell.edu>]

On 7/1/2022 1:46 AM, Lavrentiev, Anton (NIH/NLM/NCBI) [C] via Cygwin wrote:
> Now, if I run this code in my Cygwin home directory (and any directory that I create using "mkdir..." under it),
> I am getting the expected results:
> 
> $ ~/sun
> fstat mode = 140666
> stat mode = 140666
> 
> $ ls -l .socket
> srw-rw-rw-+ 1 ANTON None 0 Jul  1 01:19 .socket=
> 
> However, if I run it elsewhere (different drive "cd /cygdrive/g/cygwin" -- it's NOT where Cygwin is installed,
> just a folder that keeps files for Cygwin development, the installation is on C:\Cygwin64), I cannot predict
> the results.  What's weird is that fstat and stat report different file modes.
> 
> $ pwd
> /cygdrive/g/cygwin
> $ ~/sun
> fstat mode = 140666
> stat mode = 140666
> $ ls -l .socket
> srw-rw-rw-+ 1 ANTON None 0 Jul  1 01:24 .socket=
> 
> So all's good here, BUT:
> 
> $ mkdir subdir
> $ cd subdir
> $ pwd
> /cygdrive/g/cygwin/subdir
> $ ~/sun
> fstat mode = 140666
> stat mode = 140664
> $ ls -l .socket
> srw-rw-r--+ 1 ANTON None 0 Jul  1 01:25 .socket=
> 
> Note that fstat lied!
> 
> For some reason getfacl returns "Not supported", so I could not investigate with that

Can you give us more information about where that error is coming from?  Are you 
able to run getfacl under gdb and show us a backtrace from that point?  I often 
find it helpful to first run the program under strace in order to locate the 
source of the error, so I know where to set a breakpoint in gdb.

And what can you tell us about the drive /cygdrive/g?  The failure of getfacl 
suggests that Cygwin thinks the drive doesn't support ACLs, in which case it 
might just be faking permissions (lying).

Ken