From b301141dd36b0dc5d7289ffe504e17cf4c2921e1 Mon Sep 17 00:00:00 2001 From: Freeyorp Date: Sat, 20 Apr 2024 18:35:55 +0000 Subject: npc: Deregister events with `ev_db` on free In serverdata@c3b7fe59a, `magic-knuckles` made use of temporary copies of the spell NPC via `puppet`/`destroy` to provide additional functionality. This implementation was correct with respect to tmwa behaviour as documented. However, `puppet` and `destroy` doesn't quite return the server to a clean prior state. In `builtin_puppet`, events with the fresh new copy of NPC are registered into the global `ev_db` map to track named events, such as `OnDischarge`, which might be triggered later. However, these registrations are not reversed with `destroy`, leaving `ev_db` to retain references to now invalid and destroyed NPCs. serverdata@c3b7fe59a revealed this oversight through an intersection of rare conditions: - An NPC that is routinely cloned and destroyed - Having a variety of events - Including one that can be triggered during a search for the event over ALL NPCs when `#discharge` is cast. To reproduce, compile with `-fsanitize=address -fsanitize=undefined` to more reliably catch use of invalid memory, cast `magic-knuckles`, log out the character which cast `magic-knuckles` to destroy the NPC, log back in, then cast `#discharge`. The server will then crash. Special thanks to SystemError for testing out this theory. Currently lacking a test environment of my own, this would not have been possible without his patience and diligence. --- src/map/npc.cpp | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/src/map/npc.cpp b/src/map/npc.cpp index ee2f30c..efb2ba3 100644 --- a/src/map/npc.cpp +++ b/src/map/npc.cpp @@ -1050,6 +1050,18 @@ void npc_free_internal(dumb_ptr nd_) nd_->bl_m->npc[nd_->n] = nullptr; } + // Also clean up any events we registered to the global ev_db + if (auto nd = nd_->is_script()) + { + for (auto& pair : ev_db) + { + if (pair.second.nd == nd) + { + ev_db.erase(pair.first); + } + } + } + nd_.delete_(); } -- cgit v1.2.3-60-g2f50