normal/menu: Check return code of the script when executing a menu entry

Don't rely on grub_errno here because grub_script_execute_new_scope()
calls grub_print_error(), which always resets grub_errno back to
GRUB_ERR_NONE. It may also get reset by grub_wait_after_message().

This problem was observed when a "bad signature" error resulted in the
menu being redisplayed rather than the fallback mechanism being
triggered, although another change was also needed to fix it. This only
happens with Red Hat's patches because upstream GRUB triggers the
fallback mechanism regardless of the return code.

Signed-off-by: James Le Cuirot <[email protected]>

Author: chewi

grub-core/normal/menu.c

@@ -376,14 +376,14 @@ grub_menu_execute_entry(grub_menu_entry_t entry, int auto_boot)
   if (ptr && ptr[0] && ptr[1])
     grub_env_set ("default", ptr + 1);
 
-  grub_script_execute_new_scope (entry->sourcecode, entry->argc, entry->args);
+  err = grub_script_execute_new_scope (entry->sourcecode, entry->argc, entry->args);
 
   if (errs_before != grub_err_printed_errors)
     grub_wait_after_message ();
 
   errs_before = grub_err_printed_errors;
 
-  if (grub_errno == GRUB_ERR_NONE && grub_loader_is_loaded ())
+  if (err == GRUB_ERR_NONE && grub_loader_is_loaded ())
     /* Implicit execution of boot, only if something is loaded.  */
     err = grub_command_execute ("boot", 0, 0);