From 97881ac976c719dc5083eb8e83e8ed923759d647 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Fri, 13 Sep 2019 15:27:02 -0700
Subject: [PATCH] ircd::m::vm::eval: Fix generation and scope duration of
 event_id in array eval.

---
 ircd/m.cc       | 23 +++++++++++++++++------
 modules/m_vm.cc |  5 +++++
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/ircd/m.cc b/ircd/m.cc
index 102cb6500..ca302a6d1 100644
--- a/ircd/m.cc
+++ b/ircd/m.cc
@@ -1390,17 +1390,28 @@ ircd::m::vm::eval::eval(const json::array &pdus,
 	for(auto it(begin(events)); it != end(events); ++it) try
 	{
 		auto &event{*it};
-		if(!json::get<"event_id"_>(event))
-			event.event_id = event::id::v4
-			{
-				this->event_id, event
-			};
+
+		// If we set the event_id in the event instance we have to unset
+		// it so other contexts don't see an invalid reference.
+		const unwind event_id{[&event]
+		{
+			event.event_id = json::get<"event_id"_>(event)?
+				event.event_id:
+				m::event::id{};
+		}};
+
+		// We have to set the event_id in the event instance if it didn't come
+		// with the event JSON.
+		if(!opts.edu && !event.event_id)
+			event.event_id = opts.room_version == "3"?
+				event::id{event::id::v3{this->event_id, event}}:
+				event::id{event::id::v4{this->event_id, event}};
 
 		// When a fault::EXISTS would not actually be revealed to the user in
 		// any way we can elide a lot of grief by checking this here first and
 		// skipping the event. The query path will be adequately cached anyway.
 		if(~(opts.warnlog | opts.errorlog) & fault::EXISTS)
-			if(m::exists(event.event_id))
+			if(event.event_id && m::exists(event.event_id))
 				continue;
 
 		operator()(event);
diff --git a/modules/m_vm.cc b/modules/m_vm.cc
index 1d4c46b60..e1130616b 100644
--- a/modules/m_vm.cc
+++ b/modules/m_vm.cc
@@ -692,6 +692,11 @@ try
 		eval.event_, &event
 	};
 
+	const scope_restore<event::id> eval_event_id
+	{
+		eval.event_id, event.event_id? event.event_id : eval.event_id
+	};
+
 	// Set a member to the room_id for convenient access, without stepping on
 	// any room_id reference that exists there for whatever reason.
 	const scope_restore eval_room_id