From 38688adaad4ed0d8b2f3fc8117e6a5c9b8b64e92 Mon Sep 17 00:00:00 2001
From: Brecht Van Lommel <brecht@blender.org>
Date: Fri, 17 Mar 2023 11:17:01 +0100
Subject: [PATCH] Fix #105818: material preview invalid memory access reported
 by ASAN

Preview render depsgraphs are put in the depsgraph registry
concurrently with other threads. This was lacking a mutex lock
and a map value that remains unchanged when other elements of
the map are updated.

Pull Request: https://projects.blender.org/blender/blender/pulls/105839
---
 .../depsgraph/intern/depsgraph_registry.cc    | 42 +++++++++++++++----
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/source/blender/depsgraph/intern/depsgraph_registry.cc b/source/blender/depsgraph/intern/depsgraph_registry.cc
index 96336167b5a..dea87550542 100644
--- a/source/blender/depsgraph/intern/depsgraph_registry.cc
+++ b/source/blender/depsgraph/intern/depsgraph_registry.cc
@@ -5,6 +5,9 @@
  * \ingroup depsgraph
  */
 
+#include <memory>
+#include <mutex>
+
 #include "intern/depsgraph_registry.h"
 
 #include "BLI_utildefines.h"
@@ -13,7 +16,19 @@
 
 namespace blender::deg {
 
-using GraphRegistry = Map<Main *, VectorSet<Depsgraph *>>;
+/* Global registry for dependency graphs associated with a main database.
+ *
+ * Threads may add or remove depsgraphs for different mains concurrently
+ * (for example for preview rendering), but not the same main. */
+
+/* Use pointer for map value to ensure span returned by get_all_registered_graphs
+ * remains unchanged as other mains are added or removed. */
+typedef std::unique_ptr<VectorSet<Depsgraph *>> GraphSetPtr;
+struct GraphRegistry {
+  Map<Main *, GraphSetPtr> map;
+  std::mutex mutex;
+};
+
 static GraphRegistry &get_graph_registry()
 {
   static GraphRegistry graph_registry;
@@ -22,28 +37,37 @@ static GraphRegistry &get_graph_registry()
 
 void register_graph(Depsgraph *depsgraph)
 {
+  GraphRegistry &graph_registry = get_graph_registry();
   Main *bmain = depsgraph->bmain;
-  get_graph_registry().lookup_or_add_default(bmain).add_new(depsgraph);
+
+  std::lock_guard<std::mutex> lock{graph_registry.mutex};
+  graph_registry.map
+      .lookup_or_add_cb(bmain, []() { return std::make_unique<VectorSet<Depsgraph *>>(); })
+      ->add_new(depsgraph);
 }
 
 void unregister_graph(Depsgraph *depsgraph)
 {
   Main *bmain = depsgraph->bmain;
   GraphRegistry &graph_registry = get_graph_registry();
-  VectorSet<Depsgraph *> &graphs = graph_registry.lookup(bmain);
-  graphs.remove(depsgraph);
+
+  std::lock_guard<std::mutex> lock{graph_registry.mutex};
+  GraphSetPtr &graphs = graph_registry.map.lookup(bmain);
+  graphs->remove(depsgraph);
 
   /* If this was the last depsgraph associated with the main, remove the main entry as well. */
-  if (graphs.is_empty()) {
-    graph_registry.remove(bmain);
+  if (graphs->is_empty()) {
+    graph_registry.map.remove(bmain);
   }
 }
 
 Span<Depsgraph *> get_all_registered_graphs(Main *bmain)
 {
-  VectorSet<Depsgraph *> *graphs = get_graph_registry().lookup_ptr(bmain);
-  if (graphs != nullptr) {
-    return *graphs;
+  GraphRegistry &graph_registry = get_graph_registry();
+  std::lock_guard<std::mutex> lock{graph_registry.mutex};
+  GraphSetPtr *graphs = graph_registry.map.lookup_ptr(bmain);
+  if (graphs) {
+    return **graphs;
   }
   return {};
 }