Version 5.0.71.47 (cherry-pick)

src/zone.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/zone.h"
 
 #include <cstring>
 
 #include "src/v8.h"
 
@@ skipping 87 matching lines @@
   if (kPointerSize == 4 && kAlignment == 4) {
     position_ += ((~size) & 4) & (reinterpret_cast<intptr_t>(position_) & 4);
   } else {
     DCHECK(kAlignment >= kPointerSize);
   }
 
   // Check if the requested size is available without expanding.
   Address result = position_;
 
   const size_t size_with_redzone = size + kASanRedzoneBytes;
-  if (limit_ < position_ + size_with_redzone) {
+  const uintptr_t limit = reinterpret_cast<uintptr_t>(limit_);
+  const uintptr_t position = reinterpret_cast<uintptr_t>(position_);
+  // position_ > limit_ can be true after the alignment correction above.
+  if (limit < position || size_with_redzone > limit - position) {
     result = NewExpand(size_with_redzone);
   } else {
     position_ += size_with_redzone;
   }
 
   Address redzone_position = result + size;
   DCHECK(redzone_position + kASanRedzoneBytes == position_);
   ASAN_POISON_MEMORY_REGION(redzone_position, kASanRedzoneBytes);
 
   // Check that the result has the proper alignment and return it.
@@ skipping 96 matching lines @@
 void Zone::DeleteSegment(Segment* segment, size_t size) {
   segment_bytes_allocated_ -= size;
   Malloced::Delete(segment);
 }
 
 
 Address Zone::NewExpand(size_t size) {
   // Make sure the requested size is already properly aligned and that
   // there isn't enough room in the Zone to satisfy the request.
   DCHECK_EQ(size, RoundDown(size, kAlignment));
-  DCHECK_LT(limit_, position_ + size);
+  DCHECK(limit_ < position_ ||
+         reinterpret_cast<uintptr_t>(limit_) -
+                 reinterpret_cast<uintptr_t>(position_) <
+             size);
 
   // Compute the new segment size. We use a 'high water mark'
   // strategy, where we increase the segment size every time we expand
   // except that we employ a maximum segment size when we delete. This
   // is to avoid excessive malloc() and free() overhead.
   Segment* head = segment_head_;
   const size_t old_size = (head == nullptr) ? 0 : head->size();
   static const size_t kSegmentOverhead = sizeof(Segment) + kAlignment;
   const size_t new_size_no_overhead = size + (old_size << 1);
   size_t new_size = kSegmentOverhead + new_size_no_overhead;
@@ skipping 30 matching lines @@
   // size bytes + header and alignment padding)
   DCHECK(reinterpret_cast<uintptr_t>(position_) >=
          reinterpret_cast<uintptr_t>(result));
   limit_ = segment->end();
   DCHECK(position_ <= limit_);
   return result;
 }
 
 }  // namespace internal
 }  // namespace v8