Cygwin: shared: Fix access permissions setting in open_shared().

After the commit 93508e5bb8, the access permissions argument passed
to open_shared() is ignored and always replaced with (FILE_MAP_READ |
FILE_MAP_WRITE). This causes the weird behaviour that sshd service
process loses its cygwin PID. This triggers the failure in pty that
transfer_input() does not work properly.

This patch resumes the access permission settings to fix that.

Fixes: 93508e5bb8 ("Cygwin: open_shared: don't reuse shared_locations parameter as output")
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signedd-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>

winsup/cygwin/mm/shared.cc

@@ -139,8 +139,7 @@ open_shared (const WCHAR *name, int n, HANDLE& shared_h, DWORD size,
       if (name)
 	mapname = shared_name (map_buf, name, n);
       if (m == SH_JUSTOPEN)
-	shared_h = OpenFileMappingW (FILE_MAP_READ | FILE_MAP_WRITE, FALSE,
-				     mapname);
+	shared_h = OpenFileMappingW (access, FALSE, mapname);
       else
 	{
 	  created = true;
@@ -165,8 +164,7 @@ open_shared (const WCHAR *name, int n, HANDLE& shared_h, DWORD size,
   do
     {
       addr = (void *) next_address;
-      shared = MapViewOfFileEx (shared_h, FILE_MAP_READ | FILE_MAP_WRITE,
-				0, 0, 0, addr);
+      shared = MapViewOfFileEx (shared_h, access, 0, 0, 0, addr);
       next_address += wincap.allocation_granularity ();
       if (next_address >= SHARED_REGIONS_ADDRESS_HIGH)
 	{

winsup/cygwin/release/3.4.8

@@ -17,3 +17,6 @@ Bug Fixes
 
 - Fix memory leak in printf() regarding gdtoa-based _ldtoa_r().
   Addresses: https://cygwin.com/pipermail/cygwin/2023-July/254054.html
+
+- Fix a bug introduced in cygwin 3.4.5 that open_shared() does not set
+  access permissions as requested by its argument.