[wasm] Check data segments for zero-sized memory.

src/wasm/wasm-module.cc

 // Copyright 2015 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 <memory>
 
 #include "src/base/atomic-utils.h"
 #include "src/code-stubs.h"
 
 #include "src/macro-assembler.h"
@@ skipping 1131 matching lines @@
 
       uint32_t old_mem_size = compiled_module_->mem_size();
       Address old_mem_start =
           compiled_module_->has_memory()
               ? static_cast<Address>(
                     compiled_module_->memory()->backing_store())
               : nullptr;
       RelocateMemoryReferencesInCode(code_table, old_mem_start, mem_start,
                                      old_mem_size, mem_size);
       compiled_module_->set_memory(memory_);
+    } else if (!CheckDataSegmentsAreEmpty()) {

[titzer, 2016/11/09 17:20:31]

Why not just call LoadDataSegments(nullptr, 0)?

[ahaas, 2016/11/10 10:26:25]

Done. I also fixed another issue with non-empty memory an out-of-bounds empty
segments.

+      thrower_->TypeError("data segment does not fit");
     }
 
     //--------------------------------------------------------------------------
     // Set up the runtime support for the new instance.
     //--------------------------------------------------------------------------
     Handle<WeakCell> weak_link = factory->NewWeakCell(instance);
 
     for (int i = num_imported_functions + FLAG_skip_compiling_wasm_funcs;
          i < code_table->length(); ++i) {
       Handle<Code> code = code_table->GetValueChecked<Code>(isolate_, i);
@@ skipping 176 matching lines @@
                               import_name);
       }
     } else {
       // No function specified. Use the "default export".
       result = module;
     }
 
     return result;
   }
 
-  uint32_t EvalUint32InitExpr(WasmInitExpr& expr) {
+  uint32_t EvalUint32InitExpr(const WasmInitExpr& expr) {
     switch (expr.kind) {
       case WasmInitExpr::kI32Const:
         return expr.val.i32_const;
       case WasmInitExpr::kGlobalIndex: {
         uint32_t offset = module_->globals[expr.val.global_index].offset;
         return *reinterpret_cast<uint32_t*>(raw_buffer_ptr(globals_, offset));
       }
       default:
         UNREACHABLE();
         return 0;
     }
   }
 
   // Load data segments into the memory.
   void LoadDataSegments(Address mem_addr, size_t mem_size) {
     Handle<SeqOneByteString> module_bytes = compiled_module_->module_bytes();
-    for (auto segment : module_->data_segments) {
+    for (const WasmDataSegment& segment : module_->data_segments) {
       uint32_t dest_offset = EvalUint32InitExpr(segment.dest_addr);
       uint32_t source_size = segment.source_size;
       if (dest_offset >= mem_size || source_size >= mem_size ||
           dest_offset > (mem_size - source_size)) {
-        thrower_->RangeError(
+        thrower_->TypeError(
             "data segment (start = %u, size = %u) does not fit into memory "
             "(size = %zu)",
             dest_offset, source_size, mem_size);
         return;
       }
       byte* dest = mem_addr + dest_offset;
       const byte* src = reinterpret_cast<const byte*>(
           module_bytes->GetCharsAddress() + segment.source_offset);
       memcpy(dest, src, source_size);
     }
   }
 
+  // Returns true if all segments are empty and write to address 0.
+  bool CheckDataSegmentsAreEmpty() {
+    for (const WasmDataSegment& segment : module_->data_segments) {
+      if (segment.source_size > 0) {
+        return false;
+      }
+    }
+    return true;
+  }
+
   void WriteGlobalValue(WasmGlobal& global, Handle<Object> value) {
     double num = 0;
     if (value->IsSmi()) {
       num = Smi::cast(*value)->value();
     } else if (value->IsHeapNumber()) {
       num = HeapNumber::cast(*value)->value();
     } else {
       UNREACHABLE();
     }
     TRACE("init [globals+%u] = %lf, type = %s\n", global.offset, num,
@@ skipping 857 matching lines @@
     CHECK_NOT_NULL(result.val);
     module = const_cast<WasmModule*>(result.val);
   }
 
   Handle<WasmModuleWrapper> module_wrapper =
       WasmModuleWrapper::New(isolate, module);
 
   compiled_module->set_module_wrapper(module_wrapper);
   DCHECK(WasmCompiledModule::IsWasmCompiledModule(*compiled_module));
 }