[settings] Use list_first_entry() when unregistering child settings

Unregistering a child settings block can have almost arbitrary
effects, due to the call to apply_settings().  Avoid potentially
dereferencing a stale pointer by using list_first_entry() rather than
list_for_each_entry_safe() to iterate over the list of child settings.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/core/settings.c b/src/core/settings.c
index 5e16b27d0ef4bbc06b378d9d57ab64662428648a..85d95e6ebfbf6ceb81973e69a2cdb68bc23f1adb 100644 (file)
--- a/src/core/settings.c
+++ b/src/core/settings.c
@@ -499,10 +499,10 @@ int register_settings ( struct settings *settings, struct settings *parent,
  */
 void unregister_settings ( struct settings *settings ) {
        struct settings *child;
-       struct settings *tmp;
 
        /* Unregister child settings */
-       list_for_each_entry_safe ( child, tmp, &settings->children, siblings ) {
+       while ( ( child = list_first_entry ( &settings->children,
+                                            struct settings, siblings ) ) ) {
                unregister_settings ( child );
        }