[Backport] CVE-2024-3159: Out of bounds memory access in V8

Manual cherry-pick of patch originally reviewed on
https://chromium-review.googlesource.com/c/v8/v8/+/5401859:
Merged: [runtime] Recreate enum cache on map update if any previous map had one

If any previous map in the transition tree had an enum cache, then we
recreate one when updating the map.

Bug: 330760873
(cherry picked from commit 807cf7d0b7d96212c98ed2119e07f9b2c6a23f61)

Change-Id: Ia9ea4cf17fef60166a0c037318eb539866aac37a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5401859
Reviewed-by: Igor Sheludko <[email protected]>
Commit-Queue: Igor Sheludko <[email protected]>
Auto-Submit: Darius Mercadier <[email protected]>
Cr-Commit-Position: refs/branch-heads/12.2@{#52}
Cr-Branched-From: 6eb5a9616aa6f8c705217aeb7c7ab8c037a2f676-refs/heads/12.2.281@{#1}
Cr-Branched-From: 44cf56d850167c6988522f8981730462abc04bcc-refs/heads/main@{#91934}
Reviewed-on: https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/553302
Reviewed-by: Michal Klocek <[email protected]>

chromium/v8/src/objects/map-updater.cc

@@ -1031,14 +1031,21 @@ MapUpdater::State MapUpdater::ConstructNewMap() {
   Handle<Map> new_map =
       Map::AddMissingTransitions(isolate_, split_map, new_descriptors);
 
+  bool had_any_enum_cache =
+      split_map->instance_descriptors(isolate_)
+              .enum_cache()
+              .keys()
+              .length() > 0 ||
+      old_descriptors_->enum_cache().keys().length() > 0;
+
   // Deprecated part of the transition tree is no longer reachable, so replace
   // current instance descriptors in the "survived" part of the tree with
   // the new descriptors to maintain descriptors sharing invariant.
   split_map->ReplaceDescriptors(isolate_, *new_descriptors);
 
-  // If the old descriptors had an enum cache, make sure the new ones do too.
-  if (old_descriptors_->enum_cache().keys().length() > 0 &&
-      new_map->NumberOfEnumerableProperties() > 0) {
+  // If the old descriptors had an enum cache (or if {split_map}'s descriptors
+  // had one), make sure the new ones do too.
+  if (had_any_enum_cache && new_map->NumberOfEnumerableProperties() > 0) {
     FastKeyAccumulator::InitializeFastPropertyEnumCache(
         isolate_, new_map, new_map->NumberOfEnumerableProperties());
   }