[fuzzer] Add input validation in the beginning of the parser fuzz target.

test/fuzzer/parser.cc

 // Copyright 2016 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 <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #include "include/v8.h"
 #include "src/objects-inl.h"
 #include "src/objects.h"
 #include "src/parsing/parse-info.h"
 #include "src/parsing/parsing.h"
 #include "src/parsing/preparser.h"
 #include "test/fuzzer/fuzzer-support.h"
 
+#include <list>
+#include <cctype>
+
+bool IsValidInput(const uint8_t* data, size_t size) {
+  std::list<char> parentheses;
+  const char* ptr = reinterpret_cast<const char*>(data);
+
+  for (size_t i = 0; i != size; ++i) {
+    // Check that all characters in the data are valid.
+    if (!(std::isspace(ptr[i]) || std::isprint(ptr[i])))

[marja, 2017/05/17 08:56:20]

Coding style nit: if the body is on the next line, this needs { } 

[mmoroz, 2017/05/17 09:59:15]

Done.

+      return false;
+
+    // Check balance of parentheses in the data.
+    switch (ptr[i]) {
+      case '(':
+      case '[':
+      case '{':
+        parentheses.push_back(ptr[i]);
+        break;
+      case ')':
+        if (parentheses.back() != '(')
+          return false;
+        parentheses.pop_back();
+        break;
+      case ']':
+        if (parentheses.back() != '[')
+          return false;
+        parentheses.pop_back();
+        break;
+      case '}':
+        if (parentheses.back() != '{')
+          return false;
+        parentheses.pop_back();
+        break;
+      default:
+        break;
+    }
+  }
+
+  return parentheses.empty();
+}
+
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  if (!IsValidInput(data, size))

[marja, 2017/05/17 08:56:20]

ditto

[mmoroz, 2017/05/17 09:59:15]

Done.

+    return 0;
+
   v8_fuzzer::FuzzerSupport* support = v8_fuzzer::FuzzerSupport::Get();
   v8::Isolate* isolate = support->GetIsolate();
 
   v8::Isolate::Scope isolate_scope(isolate);
   v8::HandleScope handle_scope(isolate);
   v8::Context::Scope context_scope(support->GetContext());
   v8::TryCatch try_catch(isolate);
 
   v8::internal::Isolate* i_isolate =
       reinterpret_cast<v8::internal::Isolate*>(isolate);
   v8::internal::Factory* factory = i_isolate->factory();
 
   if (size > INT_MAX) return 0;
   v8::internal::MaybeHandle<v8::internal::String> source =
       factory->NewStringFromOneByte(
           v8::internal::Vector<const uint8_t>(data, static_cast<int>(size)));
   if (source.is_null()) return 0;
 
   v8::internal::Handle<v8::internal::Script> script =
       factory->NewScript(source.ToHandleChecked());
   v8::internal::ParseInfo info(script);
   if (!v8::internal::parsing::ParseProgram(&info, i_isolate)) {
     i_isolate->OptionalRescheduleException(true);
   }
   isolate->RequestGarbageCollectionForTesting(
       v8::Isolate::kFullGarbageCollection);
   return 0;
 }