[newlib-cygwin] cwdstuff: Don't leave from setting the CWD prematurely on init

[Corinna Vinschen <corinna at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=88443b0a2258993a20fb5d1d886860646e5202cc

commit 88443b0a2258993a20fb5d1d886860646e5202cc
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Fri Mar 3 13:55:55 2017 +0100

    cwdstuff: Don't leave from setting the CWD prematurely on init
    
    There are certain, very obscure scenarios, which render the Windows
    CWD handle inaccessible for reopening.  An easy one is, the handle can
    be NULL if the permissions of the CWD changed under the parent processes
    feet.
    
    Originally we just set errno and returned, but in case of init at
    process startup that left the "posix" member NULL and subsequent
    calls to getcwd failed with EFAULT.
    
    We now check for a NULL handle and change the reopen approach
    accordingly.  If that doesn't work, try to duplicate the handle instead.
    If duplicating fails, too, we set the dir handle to NULL and carry on.
    This will at least set posix to some valid path and subsequent getcwd
    calls won't fail.  A NULL dir handle is ok, because we already do this
    for virtual paths.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/path.cc | 50 ++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 42 insertions(+), 8 deletions(-)

diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
index ee7636d..16de025 100644
--- a/winsup/cygwin/path.cc
+++ b/winsup/cygwin/path.cc
@@ -4445,11 +4445,23 @@ cwdstuff::set (path_conv *nat_cwd, const char *posix_cwd)
 	{
 	  /* On init, just reopen Win32 CWD with desired access flags.
 	     We can access the PEB without lock, because no other thread
-	     can change the CWD. */
-	  RtlInitUnicodeString (&upath, L"");
-	  InitializeObjectAttributes (&attr, &upath,
-			OBJ_CASE_INSENSITIVE | OBJ_INHERIT,
-			peb.ProcessParameters->CurrentDirectoryHandle, NULL);
+	     can change the CWD.  However, there's a chance that the handle
+	     is NULL, even though CurrentDirectoryName isn't so we have to
+	     be careful. */
+	  if (!peb.ProcessParameters->CurrentDirectoryHandle)
+	    {
+	      InitializeObjectAttributes (&attr,
+			    &peb.ProcessParameters->CurrentDirectoryName,
+			    OBJ_CASE_INSENSITIVE | OBJ_INHERIT, NULL, NULL);
+	    }
+	  else
+	    {
+	      RtlInitUnicodeString (&upath, L"");
+	      InitializeObjectAttributes (&attr,
+			    &upath, OBJ_CASE_INSENSITIVE | OBJ_INHERIT,
+			    peb.ProcessParameters->CurrentDirectoryHandle,
+			    NULL);
+	    }
 	}
       else
 	InitializeObjectAttributes (&attr, &upath,
@@ -4474,9 +4486,31 @@ cwdstuff::set (path_conv *nat_cwd, const char *posix_cwd)
 	}
       if (!NT_SUCCESS (status))
 	{
-	  cwd_lock.release ();
-	  __seterrno_from_nt_status (status);
-	  return -1;
+	  /* Called from chdir?  Just fail. */
+	  if (nat_cwd)
+	    {
+	      cwd_lock.release ();
+	      __seterrno_from_nt_status (status);
+	      return -1;
+	    }
+	  /* Otherwise we're in init and posix hasn't been set yet.  Try to
+	     duplicate the handle instead.  If that fails, too, set dir to NULL
+	     and carry on.  This will at least set posix to some valid path at
+	     process startup, and subsequent getcwd calls don't EFAULT. */
+	  debug_printf ("WARNING: Can't reopen CWD %y '%S', status %y",
+			peb.ProcessParameters->CurrentDirectoryHandle,
+			&peb.ProcessParameters->CurrentDirectoryName,
+			status);
+	  if (!peb.ProcessParameters->CurrentDirectoryHandle
+	      || !DuplicateHandle (GetCurrentProcess (),
+			peb.ProcessParameters->CurrentDirectoryHandle,
+			GetCurrentProcess (), &h, 0, TRUE, 0))
+	    {
+	      cwd_lock.release ();
+	      if (peb.ProcessParameters->CurrentDirectoryHandle)
+		debug_printf ("...and DuplicateHandle failed with %E.");
+	      dir = NULL;
+	    }
 	}
     }
   /* Set new handle.  Note that we simply overwrite the old handle here