improve the robustness of savedefault and default.

ChangeLog

@@ -1,3 +1,12 @@
+2001-02-02  OKUJI Yoshinori  <okuji@gnu.org>
+
+	* stage2/builtins.c (savedefault_func)
+	[!SUPPORT_DISKLESS && !GRUB_UTIL]: Check if the stage2 is
+	STAGE2_ID_STAGE2. Suggested by Jochen Hoenicke.
+	
+	* stage2/stage2.c (cmain): If DEFAULT_ENTRY is out of entries,
+	reset DEFAULT_ENTRY to zero.
+	
 2001-02-02  OKUJI Yoshinori  <okuji@gnu.org>
 
 	Make savedefault workable even with Stage 1.5. Reported by

stage2/builtins.c

@@ -3080,7 +3080,14 @@ savedefault_func (char *arg, int flags)
       return 1;
     }
 
-  entryno_ptr = (int *) ((char *) buffer + STAGE2_SAVED_ENTRYNO);
+  /* Sanity check.  */
+  if (buffer[STAGE2_STAGE2_ID] != STAGE2_ID_STAGE2)
+    {
+      errnum = ERR_BAD_VERSION;
+      return 1;
+    }
+  
+  entryno_ptr = (int *) (buffer + STAGE2_SAVED_ENTRYNO);
 
   /* Check if the saved entry number differs from current entry number.  */
   if (*entryno_ptr != current_entryno)

stage2/stage2.c

@@ -957,6 +957,11 @@ cmain (void)
 	  grub_memmove (config_entries + config_len, menu_entries, menu_len);
 	  menu_entries = config_entries + config_len;
 
+	  /* Check if the default entry is present. Otherwise reset
+	     DEFAULT_ENTRY.  */
+	  if (default_entry >= num_entries)
+	    default_entry = 0;
+
 	  if (is_preset)
 	    close_preset_menu ();
 	  else