RegExp parser: Fixed unchecked numeric overflow bug.

src/parser.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3920 matching lines @@
   }
   *index_out = value;
   return true;
 }
 
 
 // QuantifierPrefix ::
 //   { DecimalDigits }
 //   { DecimalDigits , }
 //   { DecimalDigits , DecimalDigits }
+//
+// Returns true if parsing succeeds, and set the min_out and max_out
+// values. Values are set to RegExpTree::kInfinity if they overflow.
 bool RegExpParser::ParseIntervalQuantifier(int* min_out, int* max_out) {
   ASSERT_EQ(current(), '{');
   int start = position();
   Advance();
   int min = 0;
   if (!IsDecimalDigit(current())) {
     Reset(start);
     return false;
   }
   while (IsDecimalDigit(current())) {
-    min = 10 * min + (current() - '0');
+    int next = current() - '0';
+    if (min > (RegExpTree::kInfinity - next) / 10) {
+      // Overflow. Skip past remaining decimal digits and return -1.
+      do { Advance(); } while (IsDecimalDigit(current()));

[Erik Corry, 2009/02/05 11:59:36]

Does this correctly handle hitting the end of the pattern?

[Lasse Reichstein, 2009/02/05 12:54:41]

Yes. Reading current() at end of input is allowed. It gives a special value,
kEndMarker, that definitly isn't a decimal digit.

+      min = RegExpTree::kInfinity;
+      break;
+    }
+    min = 10 * min + next;
     Advance();
   }
   int max = 0;
   if (current() == '}') {
     max = min;
     Advance();
   } else if (current() == ',') {
     Advance();
     if (current() == '}') {
       max = RegExpTree::kInfinity;
       Advance();
     } else {
       while (IsDecimalDigit(current())) {
-        max = 10 * max + (current() - '0');
+        int next = current() - '0';
+        if (max > (RegExpTree::kInfinity - next) / 10) {
+          do { Advance(); } while (IsDecimalDigit(current()));
+          max = RegExpTree::kInfinity;;
+          break;
+        }
+        max = 10 * max + next;
         Advance();
       }
       if (current() != '}') {
         Reset(start);
         return false;
       }
       Advance();
     }
   } else {
     Reset(start);
@@ skipping 395 matching lines @@
                        start_position,
                        is_expression);
   return result;
 }
 
 
 #undef NEW
 
 
 } }  // namespace v8::internal