Seems like a bug with mkfifo -m

[Ken Brown]

On 5/28/2020 4:12 AM, Дмитрий Есарев via Cygwin wrote:
> Hi, all
> 
> When i ran cygwin 2.x, i used mkfifo -m 0600 file to create a named pipe with no user and group permissions.
> 
> in the latest cygwin the above command creates device with 0644 permissions. And i cant drop it to 0600:
> 
> cygcheck.exe -V
> cygcheck (cygwin) 3.1.4
> 
> $ umask 0077
> $ touch somefile; ls -l somefile
> -rw------- 1 admin absent 0 may 26 18:15 somefile
> 
> $ mkfifo -m 0600 somefifo; ls -l somefifo
> prw-r--r-- 1 admin absent 0 may 26 18:16 somefifo
> 
> $ chmod 600 somefifo; ls -l somefifo
> prw-r--r-- 1 admin absent 0 may 26 18:16 somefifo
> 
> 
> 
> In old-good cygwin 2.x the command works as expected:
> 
> $ cygcheck.exe -V
> cygcheck (cygwin) 2.9.0
> 
> $ umask
> 0022
> 
> $ mkfifo -m 0600 somefifo; ls -l somefifo
> prw------- 1 builduser Domain Users 0 May 26 18:21 somefifo

Thanks for the report.  The problem isn't with mkfifo, it's with the permission 
information reported by ls.  I did a bisection of the Cygwin development repo 
and found that the regression was introduced by the following commit:

commit f36262d56ac78f04de147746ce4a85c6155e4a23
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Wed Jan 29 15:14:05 2020 +0100

     Cygwin: stat: fix st_mode of fifos

I'll take a look if Corinna doesn't get to it first.

Ken