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[PATCH] Avoid crash on empty menu

From: Christian Franke
Subject: [PATCH] Avoid crash on empty menu
Date: Wed, 07 Nov 2007 22:41:06 +0100
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20070802 SeaMonkey/1.1.4

If grub.cfg does not contain any valid menuentry statements, an empty menu is opened. grub-emu crashes (and real grub behaves "interesting") if the first entry is selected.

The attached patch adds the missing nullptr checks.

An alternative would be to treat an empty menu as a syntax error in main.c::read_config_file(), at least if !nested.

During testing, I found the following issues:

- If the file does not exist, read_config_file() produces a memory leak, because newmenu is allocated first.

- The commands "source FILE" and "configfile FILE" open a nested normal mode shell (and produce this leak) if the file is missing. An error message should IMO be printed instead.

- The sequence "c" -> "rescue" -> "normal" appends the same entries to the existing menu, because the old entry is reused from "menu" data slot.

Thanks for any comment.


2007-11-07  Christian Franke  <address@hidden>

        * normal/menu.c (menu_run): Check for empty menu to avoid crash.
        (grub_run_menu): Likewise.

--- grub2.orig/normal/menu.c    2007-08-20 16:35:20.000000000 +0200
+++ grub2/normal/menu.c 2007-11-07 21:57:44.375000000 +0100
@@ -412,7 +412,11 @@ run_menu (grub_menu_t menu, int nested)
              goto refresh;
            case 'e':
-             grub_menu_entry_run (get_entry (menu, first + offset));
+               {
+                 grub_menu_entry_t e = get_entry (menu, first + offset);
+                 if (e)
+                   grub_menu_entry_run (e);
+               }
              goto refresh;
@@ -451,10 +455,13 @@ grub_menu_run (grub_menu_t menu, int nes
       if (boot_entry < 0)
+      e = get_entry (menu, boot_entry);
+      if (! e)
+       continue; /* menu is empty */
       grub_cls ();
       grub_setcursor (1);
-      e = get_entry (menu, boot_entry);
       grub_printf ("  Booting \'%s\'\n\n", e->title);
       run_menu_entry (e);

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