[Backport] CVE-2021-21225: Out of bounds memory access in V8 (1/2)

Cherry-pick of patch originally reviewed on
https://chromium-review.googlesource.com/c/v8/v8/+/2823829:
[LTS-M86][builtins] Fix Array.prototype.concat with @@species

(cherry picked from commit 7989e04979c3195e60a6814e8263063eb91f7b47)

No-Try: true
No-Presubmit: true
No-Tree-Checks: true
Bug: chromium:1195977
Change-Id: I16843bce2e9f776abca0f2b943b898ab5e597e42
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#73842}
Commit-Queue: Jana Grill <janagrill@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Victor-Gabriel Savu <vsavu@google.com>
Cr-Commit-Position: refs/branch-heads/8.6@{#77}
Cr-Branched-From: a64aed2333abf49e494d2a5ce24bbd14fff19f60-refs/heads/8.6.395@{#1}
Cr-Branched-From: a626bc036236c9bf92ac7b87dc40c9e538b087e3-refs/heads/master@{#69472}
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

chromium/v8/src/builtins/builtins-array.cc

@@ -649,11 +649,14 @@ class ArrayConcatVisitor {
         index_offset_(0u),
         bit_field_(FastElementsField::encode(fast_elements) |
                    ExceedsLimitField::encode(false) |
-                   IsFixedArrayField::encode(storage->IsFixedArray()) |
+                   IsFixedArrayField::encode(storage->IsFixedArray(isolate)) |
                    HasSimpleElementsField::encode(
-                       storage->IsFixedArray() ||
-                       !storage->map().IsCustomElementsReceiverMap())) {
-    DCHECK(!(this->fast_elements() && !is_fixed_array()));
+                       storage->IsFixedArray(isolate) ||
+                       // Don't take fast path for storages that might have
+                       // side effects when storing to them.
+                       (!storage->map(isolate).IsCustomElementsReceiverMap() &&
+                        !storage->IsJSTypedArray(isolate)))) {
+    DCHECK_IMPLIES(this->fast_elements(), is_fixed_array());
   }
 
   ~ArrayConcatVisitor() { clear_storage(); }
@@ -1063,8 +1066,8 @@ bool IterateElements(Isolate* isolate, Handle<JSReceiver> receiver,
     return IterateElementsSlow(isolate, receiver, length, visitor);
   }
 
-  if (!HasOnlySimpleElements(isolate, *receiver) ||
-      !visitor->has_simple_elements()) {
+  if (!visitor->has_simple_elements() ||
+      !HasOnlySimpleElements(isolate, *receiver)) {
     return IterateElementsSlow(isolate, receiver, length, visitor);
   }
   Handle<JSObject> array = Handle<JSObject>::cast(receiver);

chromium/v8/src/objects/fixed-array-inl.h

@@ -336,15 +336,15 @@ int Search(T* array, Name name, int valid_entries, int* out_insertion_index,
 double FixedDoubleArray::get_scalar(int index) {
   DCHECK(map() != GetReadOnlyRoots().fixed_cow_array_map() &&
          map() != GetReadOnlyRoots().fixed_array_map());
-  DCHECK(index >= 0 && index < this->length());
+  DCHECK_LT(static_cast<unsigned>(index), static_cast<unsigned>(length()));
   DCHECK(!is_the_hole(index));
   return ReadField<double>(kHeaderSize + index * kDoubleSize);
 }
 
 uint64_t FixedDoubleArray::get_representation(int index) {
   DCHECK(map() != GetReadOnlyRoots().fixed_cow_array_map() &&
          map() != GetReadOnlyRoots().fixed_array_map());
-  DCHECK(index >= 0 && index < this->length());
+  DCHECK_LT(static_cast<unsigned>(index), static_cast<unsigned>(length()));
   int offset = kHeaderSize + index * kDoubleSize;
   // Bug(v8:8875): Doubles may be unaligned.
   return base::ReadUnalignedValue<uint64_t>(field_address(offset));
@@ -362,6 +362,7 @@ Handle<Object> FixedDoubleArray::get(FixedDoubleArray array, int index,
 void FixedDoubleArray::set(int index, double value) {
   DCHECK(map() != GetReadOnlyRoots().fixed_cow_array_map() &&
          map() != GetReadOnlyRoots().fixed_array_map());
+  DCHECK_LT(static_cast<unsigned>(index), static_cast<unsigned>(length()));
   int offset = kHeaderSize + index * kDoubleSize;
   if (std::isnan(value)) {
     WriteField<double>(offset, std::numeric_limits<double>::quiet_NaN());
@@ -378,6 +379,7 @@ void FixedDoubleArray::set_the_hole(Isolate* isolate, int index) {
 void FixedDoubleArray::set_the_hole(int index) {
   DCHECK(map() != GetReadOnlyRoots().fixed_cow_array_map() &&
          map() != GetReadOnlyRoots().fixed_array_map());
+  DCHECK_LT(static_cast<unsigned>(index), static_cast<unsigned>(length()));
   int offset = kHeaderSize + index * kDoubleSize;
   base::WriteUnalignedValue<uint64_t>(field_address(offset), kHoleNanInt64);
 }