Fixes long-standing random hang of exec.

2009-05-25  Samuel Thibault  <samuel.thibault@ens-lyon.org>

	* exec.c (finish): Set FILE_DATA and MAP_BUFFER members of E to NULL
	after freeing them.

Index: exec/exec.c
===================================================================
RCS file: /cvsroot/hurd/hurd/exec/exec.c,v
retrieving revision 1.93
diff -u -p -r1.93 exec.c
--- exec/exec.c	2 Apr 2009 23:06:37 -0000	1.93
+++ exec/exec.c	25 May 2009 09:39:35 -0000
@@ -1008,10 +1008,13 @@ finish (struct execdata *e, int dealloc_
 #ifdef EXECDATA_STREAM
       fclose (&e->stream);
 #else
-      if (e->file_data != NULL)
+      if (e->file_data != NULL) {
 	free (e->file_data);
-      else if (map_buffer (e) != NULL)
+	e->file_data = NULL;
+      } else if (map_buffer (e) != NULL) {
 	munmap (map_buffer (e), map_vsize (e));
+	map_buffer (e) = NULL;
+      }
 #endif
     }
   if (dealloc_file && e->file != MACH_PORT_NULL)