[newlib-cygwin] Cygwin: AF_UNIX: use FILE_OPEN_REPARSE_POINT when needed

[Ken Brown <kbrown@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=4b4fffe0f2390be6a5be27b6a3ceaa212a3724b2

commit 4b4fffe0f2390be6a5be27b6a3ceaa212a3724b2
Author: Ken Brown <kbrown@cornell.edu>
Date:   Mon Sep 28 15:57:56 2020 -0400

    Cygwin: AF_UNIX: use FILE_OPEN_REPARSE_POINT when needed
    
    The following Windows system calls currently fail with
    STATUS_IO_REPARSE_TAG_NOT_HANDLED when called on an AF_UNIX socket:
    
    - NtOpenFile in get_file_sd
    
    - NtOpenFile in set_file_sd
    
    - NtCreateFile in fhandler_base::open
    
    Fix this by adding the FILE_OPEN_REPARSE_POINT flag to those calls
    when the file is a known reparse point.

Diff:
---
 winsup/cygwin/fhandler.cc | 11 +++++++++--
 winsup/cygwin/security.cc |  8 ++++++--
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/winsup/cygwin/fhandler.cc b/winsup/cygwin/fhandler.cc
index 82b21aff4..5dbbd4068 100644
--- a/winsup/cygwin/fhandler.cc
+++ b/winsup/cygwin/fhandler.cc
@@ -620,13 +620,20 @@ fhandler_base::open (int flags, mode_t mode)
   else
     create_disposition = (flags & O_CREAT) ? FILE_OPEN_IF : FILE_OPEN;
 
-  if (get_device () == FH_FS)
+  if (get_device () == FH_FS
+#ifdef __WITH_AF_UNIX
+      || get_device () == FH_UNIX
+#endif
+      )
     {
-      /* Add the reparse point flag to known repares points, otherwise we
+      /* Add the reparse point flag to known reparse points, otherwise we
 	 open the target, not the reparse point.  This would break lstat. */
       if (pc.is_known_reparse_point ())
 	options |= FILE_OPEN_REPARSE_POINT;
+    }
 
+  if (get_device () == FH_FS)
+    {
       /* O_TMPFILE files are created with delete-on-close semantics, as well
 	 as with FILE_ATTRIBUTE_TEMPORARY.  The latter speeds up file access,
 	 because the OS tries to keep the file in memory as much as possible.
diff --git a/winsup/cygwin/security.cc b/winsup/cygwin/security.cc
index 468b05164..d48526619 100644
--- a/winsup/cygwin/security.cc
+++ b/winsup/cygwin/security.cc
@@ -65,7 +65,9 @@ get_file_sd (HANDLE fh, path_conv &pc, security_descriptor &sd,
 			   fh ? pc.init_reopen_attr (attr, fh)
 			      : pc.get_object_attr (attr, sec_none_nih),
 			   &io, FILE_SHARE_VALID_FLAGS,
-			   FILE_OPEN_FOR_BACKUP_INTENT);
+			   FILE_OPEN_FOR_BACKUP_INTENT
+			   | pc.is_known_reparse_point ()
+			   ? FILE_OPEN_REPARSE_POINT : 0);
       if (!NT_SUCCESS (status))
 	{
 	  sd.free ();
@@ -232,7 +234,9 @@ set_file_sd (HANDLE fh, path_conv &pc, security_descriptor &sd, bool is_chown)
 				  : pc.get_object_attr (attr, sec_none_nih),
 			       &io,
 			       FILE_SHARE_VALID_FLAGS,
-			       FILE_OPEN_FOR_BACKUP_INTENT);
+			       FILE_OPEN_FOR_BACKUP_INTENT
+			       | pc.is_known_reparse_point ()
+			       ? FILE_OPEN_REPARSE_POINT : 0);
 	  if (!NT_SUCCESS (status))
 	    {
 	      fh = NULL;