When mounting with "modefromsid" retrieve mode bits from
special SID (S-1-5-88-3) on stat.  Subsequent patch will fix
setattr (chmod) to save mode bits in S-1-5-88-3-<mode>

Note that when an ACE matching S-1-5-88-3 is not found, we
default the mode to an approximation based on the owner, group
and everyone permissions (as with the "cifsacl" mount option).

See See e.g.
    https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/hh509017(v=ws.10)

Below is an example of 3 files created (over NFS to Windows) with
three different modes, and note that their permissions now display
accurately:

# stat /mnt-to-windows/file0777
  File: /mnt-to-windows/file0777
  Size: 0          Blocks: 0          IO Block: 1048576 regular empty file
Device: 33h/51d Inode: 4785074604105433  Links: 1
Access: (0777/-rwxrwxrwx)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2019-07-19 01:31:53.728517100 +0000
Modify: 2019-07-19 01:31:53.728517100 +0000
Change: 2019-07-19 01:36:40.588153100 +0000
 Birth: -

# stat /mnt-to-windows/file0400
  File: /mnt-to-windows/file0400
  Size: 0          Blocks: 0          IO Block: 1048576 regular empty file
Device: 33h/51d Inode: 1970324836998972  Links: 1
Access: (0400/-r--------)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2019-07-19 01:31:55.760662400 +0000
Modify: 2019-07-19 01:31:55.760662400 +0000
Change: 2019-07-19 01:36:40.588153100 +0000
 Birth: -

# stat /mnt-to-windows/file3777
  File: /mnt-to-windows/file3777
  Size: 0          Blocks: 0          IO Block: 1048576 regular empty file
Device: 33h/51d Inode: 1407374883577661  Links: 1
Access: (3777/-rwxrwsrwt)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2019-07-19 01:32:01.653725200 +0000
Modify: 2019-07-19 01:32:01.653725200 +0000
Change: 2019-07-19 01:36:40.588153100 +0000


-- 
Thanks,

Steve