Check that array length stays a safe integer in Array.prototype.push

src/js/array.js

Index: src/js/array.js
diff --git a/src/js/array.js b/src/js/array.js
index b13e4e239223093af848f17b0b61d4a02390e371..d84635653cd0b34f9585ee5c2546b26a8be6a52b 100644
--- a/src/js/array.js
+++ b/src/js/array.js
@@ -517,6 +517,15 @@ function ArrayPush() {
   var n = TO_LENGTH_OR_UINT32(array.length);
   var m = %_ArgumentsLength();
 
+  // It appears that there is no enforced, absolute limit on the number of
+  // arguments, but it would be very slow for users to use 2**32 or more.
+  // To avoid integer overflow, do the comparison to the max safe integer
+  // after subtracting 2**32 from both sides. To stay on the safe side, also
+  // prohibit this function from being called with more than 2**32 arguments.
+  if (m > 1 << 32 || (n - (1 << 32)) + m > kMaxSafeInteger - (1 << 32)) {

[adamk, 2015/10/26 23:14:28]

"1 << 32" isn't doing what you want. It returns 1...

[Dan Ehrenberg, 2015/10/27 00:47:36]

Right. I finally settled on something that works, WDYT?

+    throw MakeTypeError(kPushPastSafeLength, m, n);
+  }
+
   for (var i = 0; i < m; i++) {
     array[i+n] = %_Arguments(i);
   }