From c70ca686fe269db6079a2ca1c7e09cdfc0cfa903 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Mon, 5 Sep 2016 16:16:23 +0200 Subject: Don't leak old code when loading a modules with an on_load function Normally, calling code:delete/1 before re-loading the code for a module is unnecessary but causes no problem. But there will be be problems if the new code has an on_load function. Code with an on_load function will always be loaded as old code to allowed it to be easily purged if the on_load function would fail. If the on_load function succeeds, the old and current code will be swapped. So in the scenario where code:delete/1 has been called explicitly, there is old code but no current code. Loading code with an on_load function will cause the reference to the old code to be overwritten. That will at best cause a memory leak, and at worst an emulator crash (especially if NIFs are involved). To avoid that situation, we will put the code with the on_load function in a special, third slot in Module. ERL-240 --- erts/emulator/beam/module.h | 1 + 1 file changed, 1 insertion(+) (limited to 'erts/emulator/beam/module.h') diff --git a/erts/emulator/beam/module.h b/erts/emulator/beam/module.h index 5a60bc90d9..1c1afc8461 100644 --- a/erts/emulator/beam/module.h +++ b/erts/emulator/beam/module.h @@ -39,6 +39,7 @@ typedef struct erl_module { struct erl_module_instance curr; struct erl_module_instance old; /* protected by "old_code" rwlock */ + struct erl_module_instance* on_load; } Module; Module* erts_get_module(Eterm mod, ErtsCodeIndex code_ix); -- cgit v1.2.3