ACL: Why SYSTEM doesn't have full access set on newly created files?

[Biswapriyo Nath]

Same issue here. I use git in msys2 for correct file permissions. Also
if I install cygwin and reinstall Windows 10 OS then Windows programs
can not edit any cygwin files. I have to take ownership with takeown
and icacls commands then chmod the files.

I found a temporary workaround. 1. Add `noacl` option in `/etc/fstab`
file in cygwin. But this only fixes the file permission in Windows
drives . 2. In newlib-cygwin source code, remove
`FILE_PERSISTENT_ACLS` flag and add `MOUNT_NOACL` flag in
winsup/cygwin/mount.cc file. Attached patch file as reference.
-------------- next part --------------
diff --git a/winsup/cygwin/mount.cc b/winsup/cygwin/mount.cc
index e034981..7ba6f4a 100644
--- a/winsup/cygwin/mount.cc
+++ b/winsup/cygwin/mount.cc
@@ -332,7 +332,6 @@ fs_info::update (PUNICODE_STRING upath, HANDLE in_vol)
 #define MINIMAL_WIN_NTFS_FLAGS (FILE_CASE_SENSITIVE_SEARCH \
 				| FILE_CASE_PRESERVED_NAMES \
 				| FILE_UNICODE_ON_DISK \
-				| FILE_PERSISTENT_ACLS \
 				| FILE_FILE_COMPRESSION \
 				| FILE_VOLUME_QUOTAS \
 				| FILE_SUPPORTS_SPARSE_FILES \
@@ -473,13 +472,13 @@ mount_info::create_root_entry (const PWCHAR root)
   sys_wcstombs (native_root, PATH_MAX, root);
   assert (*native_root != '\0');
   if (add_item (native_root, "/",
-		MOUNT_SYSTEM | MOUNT_IMMUTABLE | MOUNT_AUTOMATIC)
+		MOUNT_SYSTEM | MOUNT_IMMUTABLE | MOUNT_AUTOMATIC | MOUNT_NOACL)
       < 0)
     api_fatal ("add_item (\"%s\", \"/\", ...) failed, errno %d", native_root, errno);
   /* Create a default cygdrive entry.  Note that this is a user entry.
      This allows to override it with mount, unless the sysadmin created
      a cygdrive entry in /etc/fstab. */
-  cygdrive_flags = MOUNT_NOPOSIX | MOUNT_CYGDRIVE;
+  cygdrive_flags = MOUNT_NOPOSIX | MOUNT_CYGDRIVE | MOUNT_NOACL;
   strcpy (cygdrive, CYGWIN_INFO_CYGDRIVE_DEFAULT_PREFIX "/");
   cygdrive_len = strlen (cygdrive);
 }
@@ -508,12 +507,12 @@ mount_info::init (bool user_init)
       if (!got_usr_bin)
       {
 	stpcpy (p, "\\bin");
-	add_item (native, "/usr/bin", MOUNT_SYSTEM | MOUNT_AUTOMATIC);
+	add_item (native, "/usr/bin", MOUNT_SYSTEM | MOUNT_AUTOMATIC | MOUNT_NOACL);
       }
       if (!got_usr_lib)
       {
 	stpcpy (p, "\\lib");
-	add_item (native, "/usr/lib", MOUNT_SYSTEM | MOUNT_AUTOMATIC);
+	add_item (native, "/usr/lib", MOUNT_SYSTEM | MOUNT_AUTOMATIC | MOUNT_NOACL);
       }
     }
 }
@@ -1131,7 +1130,7 @@ mount_info::from_fstab_line (char *line, bool user)
     return true;
   cend = find_ws (c);
   *cend = '\0';
-  unsigned mount_flags = MOUNT_SYSTEM;
+  unsigned mount_flags = MOUNT_SYSTEM | MOUNT_NOPOSIX | MOUNT_NOACL;
   if (!strcmp (fs_type, "cygdrive"))
     mount_flags |= MOUNT_NOPOSIX;
   if (!strcmp (fs_type, "usertemp"))