[Backport] CVE-2022-4262: Type Confusion in V8

Cherry-pick of patch originally reviewed on
https://chromium-review.googlesource.com/c/v8/v8/+/4066543:
Merged: [parser] Fix eval tracking

Due to mismatch in strictness we otherwise invalidly mark scopes as
calling sloppy eval.

Bug: chromium:1394403
(cherry picked from commit 27fa951ae4a3801126e84bc94d5c82dd2370d18b)

Change-Id: I292a86ed117638c6b569b8f1c5a37e5b9eb254c1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4066543
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/branch-heads/10.8@{#40}
Cr-Branched-From: f1bc03fd6b4c201abd9f0fd9d51fb989150f97b9-refs/heads/10.8.168@{#1}
Cr-Branched-From: 237de893e1c0a0628a57d0f5797483d3add7f005-refs/heads/main@{#83672}
Reviewed-on: https://codereview.qt-project.org/c/qt/qtwebengine-chromium/+/447565
Reviewed-by: Michal Klocek <michal.klocek@qt.io>

2 files changed, 40 insertions, 60 deletions

diff --git a/chromium/v8/src/ast/scopes.cc b/chromium/v8/src/ast/scopes.cc
index 679472c7c62..54709de5b74 100644
--- a/chromium/v8/src/ast/scopes.cc
+++ b/chromium/v8/src/ast/scopes.cc
@@ -888,9 +888,8 @@ void DeclarationScope::AddLocal(Variable* var) {
 }
 
 void Scope::Snapshot::Reparent(DeclarationScope* new_parent) {
-  DCHECK(!IsCleared());
-  DCHECK_EQ(new_parent, outer_scope_and_calls_eval_.GetPointer()->inner_scope_);
-  DCHECK_EQ(new_parent->outer_scope_, outer_scope_and_calls_eval_.GetPointer());
+  DCHECK_EQ(new_parent, outer_scope_->inner_scope_);
+  DCHECK_EQ(new_parent->outer_scope_, outer_scope_);
   DCHECK_EQ(new_parent, new_parent->GetClosureScope());
   DCHECK_NULL(new_parent->inner_scope_);
   DCHECK(new_parent->unresolved_list_.is_empty());
@@ -915,12 +914,11 @@ void Scope::Snapshot::Reparent(DeclarationScope* new_parent) {
     new_parent->sibling_ = top_inner_scope_;
   }
 
-  Scope* outer_scope = outer_scope_and_calls_eval_.GetPointer();
-  new_parent->unresolved_list_.MoveTail(&outer_scope->unresolved_list_,
+  new_parent->unresolved_list_.MoveTail(&outer_scope_->unresolved_list_,
                                         top_unresolved_);
 
   // Move temporaries allocated for complex parameter initializers.
-  DeclarationScope* outer_closure = outer_scope->GetClosureScope();
+  DeclarationScope* outer_closure = outer_scope_->GetClosureScope();
   for (auto it = top_local_; it != outer_closure->locals()->end(); ++it) {
     Variable* local = *it;
     DCHECK_EQ(VariableMode::kTemporary, local->mode());
@@ -932,16 +930,10 @@ void Scope::Snapshot::Reparent(DeclarationScope* new_parent) {
   outer_closure->locals_.Rewind(top_local_);
 
   // Move eval calls since Snapshot's creation into new_parent.
-  if (outer_scope_and_calls_eval_->calls_eval_) {
-    new_parent->RecordDeclarationScopeEvalCall();
-    new_parent->inner_scope_calls_eval_ = true;
+  if (outer_scope_->calls_eval_) {
+    new_parent->RecordEvalCall();
+    declaration_scope_->sloppy_eval_can_extend_vars_ = false;
   }
-
-  // We are in the arrow function case. The calls eval we may have recorded
-  // is intended for the inner scope and we should simply restore the
-  // original "calls eval" flag of the outer scope.
-  RestoreEvalFlag();
-  Clear();
 }
 
 void Scope::ReplaceOuterScope(Scope* outer) {
@@ -2579,6 +2571,9 @@ void Scope::AllocateVariablesRecursively() {
   this->ForEach([](Scope* scope) -> Iteration {
     DCHECK(!scope->already_resolved_);
     if (WasLazilyParsed(scope)) return Iteration::kContinue;
+    if (scope->sloppy_eval_can_extend_vars_) {
+      scope->num_heap_slots_ = Context::MIN_CONTEXT_EXTENDED_SLOTS;
+    }
     DCHECK_EQ(scope->ContextHeaderLength(), scope->num_heap_slots_);
 
     // Allocate variables for this scope.
diff --git a/chromium/v8/src/ast/scopes.h b/chromium/v8/src/ast/scopes.h
index 6f701ead0b1..c414280589b 100644
--- a/chromium/v8/src/ast/scopes.h
+++ b/chromium/v8/src/ast/scopes.h
@@ -112,12 +112,6 @@ class V8_EXPORT_PRIVATE Scope : public NON_EXPORTED_BASE(ZoneObject) {
 
   class Snapshot final {
    public:
-    Snapshot()
-        : outer_scope_and_calls_eval_(nullptr, false),
-          top_unresolved_(),
-          top_local_() {
-      DCHECK(IsCleared());
-    }
     inline explicit Snapshot(Scope* scope);
 
     // Disallow copy and move.
@@ -125,45 +119,31 @@ class V8_EXPORT_PRIVATE Scope : public NON_EXPORTED_BASE(ZoneObject) {
     Snapshot(Snapshot&&) = delete;
 
     ~Snapshot() {
-      // If we're still active, there was no arrow function. In that case outer
-      // calls eval if it already called eval before this snapshot started, or
-      // if the code during the snapshot called eval.
-      if (!IsCleared() && outer_scope_and_calls_eval_.GetPayload()) {
-        RestoreEvalFlag();
+      // Restore eval flags from before the scope was active.
+      if (sloppy_eval_can_extend_vars_) {
+        declaration_scope_->sloppy_eval_can_extend_vars_ = true;
       }
-    }
-
-    void RestoreEvalFlag() {
-      if (outer_scope_and_calls_eval_.GetPayload()) {
-        // This recreates both calls_eval and sloppy_eval_can_extend_vars.
-        outer_scope_and_calls_eval_.GetPointer()->RecordEvalCall();
+      if (calls_eval_) {
+        outer_scope_->calls_eval_ = true;
       }
     }
 
     void Reparent(DeclarationScope* new_parent);
-    bool IsCleared() const {
-      return outer_scope_and_calls_eval_.GetPointer() == nullptr;
-    }
-
-    void Clear() {
-      outer_scope_and_calls_eval_.SetPointer(nullptr);
-#ifdef DEBUG
-      outer_scope_and_calls_eval_.SetPayload(false);
-      top_inner_scope_ = nullptr;
-      top_local_ = base::ThreadedList<Variable>::Iterator();
-      top_unresolved_ = UnresolvedList::Iterator();
-#endif
-    }
 
    private:
-    // During tracking calls_eval caches whether the outer scope called eval.
-    // Upon move assignment we store whether the new inner scope calls eval into
-    // the move target calls_eval bit, and restore calls eval on the outer
-    // scope.
-    base::PointerWithPayload<Scope, bool, 1> outer_scope_and_calls_eval_;
+    Scope* outer_scope_;
+    Scope* declaration_scope_;
     Scope* top_inner_scope_;
     UnresolvedList::Iterator top_unresolved_;
     base::ThreadedList<Variable>::Iterator top_local_;
+    // While the scope is active, the scope caches the flag values for
+    // outer_scope_ / declaration_scope_ they can be used to know what happened
+    // while parsing the arrow head. If this turns out to be an arrow head, new
+    // values on the respective scopes will be cleared and moved to the inner
+    // scope. Otherwise the cached flags will be merged with the flags from the
+    // arrow head.
+    bool calls_eval_;
+    bool sloppy_eval_can_extend_vars_;
   };
 
   enum class DeserializationMode { kIncludingVariables, kScopesOnly };
@@ -909,8 +889,8 @@ class V8_EXPORT_PRIVATE DeclarationScope : public Scope {
   void RecordDeclarationScopeEvalCall() {
     calls_eval_ = true;
 
-    // If this isn't a sloppy eval, we don't care about it.
-    if (language_mode() != LanguageMode::kSloppy) return;
+    // The caller already checked whether we're in sloppy mode.
+    CHECK(is_sloppy(language_mode()));
 
     // Sloppy eval in script scopes can only introduce global variables anyway,
     // so we don't care that it calls sloppy eval.
@@ -944,7 +924,6 @@ class V8_EXPORT_PRIVATE DeclarationScope : public Scope {
     }
 
     sloppy_eval_can_extend_vars_ = true;
-    num_heap_slots_ = Context::MIN_CONTEXT_EXTENDED_SLOTS;
   }
 
   bool sloppy_eval_can_extend_vars() const {
@@ -1369,7 +1348,9 @@ class V8_EXPORT_PRIVATE DeclarationScope : public Scope {
 
 void Scope::RecordEvalCall() {
   calls_eval_ = true;
-  GetDeclarationScope()->RecordDeclarationScopeEvalCall();
+  if (is_sloppy(language_mode())) {
+    GetDeclarationScope()->RecordDeclarationScopeEvalCall();
+  }
   RecordInnerScopeEvalCall();
   // The eval contents might access "super" (if it's inside a function that
   // binds super).
@@ -1382,14 +1363,18 @@ void Scope::RecordEvalCall() {
 }
 
 Scope::Snapshot::Snapshot(Scope* scope)
-    : outer_scope_and_calls_eval_(scope, scope->calls_eval_),
+    : outer_scope_(scope),
+      declaration_scope_(scope->GetDeclarationScope()),
       top_inner_scope_(scope->inner_scope_),
       top_unresolved_(scope->unresolved_list_.end()),
-      top_local_(scope->GetClosureScope()->locals_.end()) {
-  // Reset in order to record eval calls during this Snapshot's lifetime.
-  outer_scope_and_calls_eval_.GetPointer()->calls_eval_ = false;
-  outer_scope_and_calls_eval_.GetPointer()->sloppy_eval_can_extend_vars_ =
-      false;
+      top_local_(scope->GetClosureScope()->locals_.end()),
+      calls_eval_(outer_scope_->calls_eval_),
+      sloppy_eval_can_extend_vars_(
+          declaration_scope_->sloppy_eval_can_extend_vars_) {
+  // Reset in order to record (sloppy) eval calls during this Snapshot's
+  // lifetime.
+  outer_scope_->calls_eval_ = false;
+  declaration_scope_->sloppy_eval_can_extend_vars_ = false;
 }
 
 class ModuleScope final : public DeclarationScope {