fixup! landlock/coalesced_hash: Implement insert

Author: micromaomao

security/landlock/coalesced_hash.h

@@ -152,6 +152,7 @@ __h_insert_get_next_free(struct h_insert_scratch *scratch,
 			 element_is_empty_t is_empty_func)
 {
 	h_index_t index_to_ret = scratch->next_free_index;
+	void *free_slot;
 
 	if (WARN_ON_ONCE(index_to_ret >= scratch->table_size)) {
 		/*
@@ -161,6 +162,16 @@ __h_insert_get_next_free(struct h_insert_scratch *scratch,
 		return 0;
 	}
 
+	free_slot = scratch->table + index_to_ret * scratch->elem_size;
+	while (!is_empty_func(free_slot)) {
+		if (WARN_ON_ONCE(index_to_ret == 0)) {
+			/* We unexpectedly used up all slots. */
+			return 0;
+		}
+		index_to_ret--;
+		free_slot = scratch->table + index_to_ret * scratch->elem_size;
+	}
+
 	if (index_to_ret == 0)
 		scratch->next_free_index = scratch->table_size;
 	else