Fix several potential buffer over-read errors in JSONParser::ConsumeNumber.

base/json/json_parser.cc

 // Copyright (c) 2012 The Chromium 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 "base/json/json_parser.h"
 
 #include <cmath>
 #include <utility>
 
 #include "base/logging.h"
@@ skipping 662 matching lines @@
   if (*pos_ == '-')
     NextChar();
 
   if (!ReadInt(false)) {
     ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
     return nullptr;
   }
   end_index = index_;
 
   // The optional fraction part.
-  if (*pos_ == '.') {
-    if (!CanConsume(1)) {
-      ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
-      return nullptr;
-    }
+  if (CanConsume(1) && *pos_ == '.') {
     NextChar();
     if (!ReadInt(true)) {
       ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
       return nullptr;
     }
     end_index = index_;
   }
 
   // Optional exponent part.
-  if (*pos_ == 'e' || *pos_ == 'E') {
+  if (CanConsume(1) && (*pos_ == 'e' || *pos_ == 'E')) {
     NextChar();
-    if (*pos_ == '-' || *pos_ == '+')
+    if (!CanConsume(1)) {
+      ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
+      return nullptr;
+    }
+    if (*pos_ == '-' || *pos_ == '+') {
       NextChar();
+    }
     if (!ReadInt(true)) {
       ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
       return nullptr;
     }
     end_index = index_;
   }
 
   // ReadInt is greedy because numbers have no easily detectable sentinel,
   // so save off where the parser should be on exit (see Consume invariant at
   // the top of the header), then make sure the next token is one which is
@@ skipping 24 matching lines @@
   double num_double;
   if (StringToDouble(num_string.as_string(), &num_double) &&
       std::isfinite(num_double)) {
     return base::MakeUnique<FundamentalValue>(num_double);
   }
 
   return nullptr;
 }
 
 bool JSONParser::ReadInt(bool allow_leading_zeros) {
-  char first = *pos_;
-  int len = 0;
+  size_t len = 0;
+  char first = 0;
 
-  char c = first;
-  while (CanConsume(1) && IsAsciiDigit(c)) {
-    c = *NextChar();
+  while (CanConsume(1)) {
+    if (!IsAsciiDigit(*pos_))
+      break;
+
+    if (len == 0)
+      first = *pos_;
+
     ++len;
+    NextChar();
   }
 
   if (len == 0)
     return false;
 
   if (!allow_leading_zeros && len > 1 && first == '0')
     return false;
 
   return true;
 }
@@ skipping 56 matching lines @@
                                            const std::string& description) {
   if (line || column) {
     return StringPrintf("Line: %i, column: %i, %s",
         line, column, description.c_str());
   }
   return description;
 }
 
 }  // namespace internal
 }  // namespace base