CVE request: Heap read out-of-bounds parsing a Javascript file with the last revision of JavaScript Core

[Gustavo Grieco <gustavo.grieco () gmail com>]

Hi,

We recently found a read out-of-bounds parsing JavaScript code in the last
revision of WebKit (
https://github.com/WebKit/webkit/commit/fcf81f3ad83cd910727c7a1824e50377a474c8f4).
I tested this issue in ArchLinux (x86_64) but other configurations could be
affected. To reproduce:

1. Recompile jsc with ASAN support.
2. Execute:

$ ./jsc red.-4050783292692436029.nkpzevdpie.js
...
=================================================================
==24637==ERROR: AddressSanitizer: heap-buffer-overflow on address
0x603000014fc8 at pc 0x7ffff67f04b0 bp 0x7fffaccf8820 sp 0x7fffaccf8810
READ of size 16 at 0x603000014fc8 thread T2
==24637==AddressSanitizer: while reporting a bug found another one.
Ignoring.
    #0 0x7ffff67f04af in WTF::(anonymous namespace)::lockHashtable()
(/home/g/Work/Code/webkit-master/WebKitBuild/Release/lib/libjavascriptcoregtk-4.0.so.18+0x20cc4af)
    #1 0x7ffff67f1b6c in WTF::ParkingLot::parkConditionallyImpl(void
const*, WTF::ScopedLambda<bool ()> const&, WTF::ScopedLambda<void ()>
const&, std::chrono::time_point<std::chrono::_V2::steady_clock,
std::chrono::duration<long, std::ratio<1l, 1000000000l> > >)
(/home/g/Work/Code/webkit-master/WebKitBuild/Release/lib/libjavascriptcoregtk-4.0.so.18+0x20cdb6c)
    #2 0x7ffff67cc1cb in std::_Function_handler<void (),
WTF::AutomaticThread::start(WTF::Locker<WTF::LockBase>
const&)::{lambda()#1}>::_M_invoke(std::_Any_data const&)
(/home/g/Work/Code/webkit-master/WebKitBuild/Release/lib/libjavascriptcoregtk-4.0.so.18+0x20a81cb)
    #3 0x7ffff67f7da5 in WTF::threadEntryPoint(void*)
(/home/g/Work/Code/webkit-master/WebKitBuild/Release/lib/libjavascriptcoregtk-4.0.so.18+0x20d3da5)
    #4 0x7ffff685a530 in WTF::wtfThreadEntryPoint(void*)
(/home/g/Work/Code/webkit-master/WebKitBuild/Release/lib/libjavascriptcoregtk-4.0.so.18+0x2136530)
    #5 0x7ffff1df1453 in start_thread (/usr/lib/libpthread.so.0+0x7453)
    #6 0x7ffff0c017de in __GI___clone (/usr/lib/libc.so.6+0xe87de)

0x603000014fd0 is located 0 bytes to the right of 32-byte region
[0x603000014fb0,0x603000014fd0)
allocated by thread T2 here:
    #0 0x7ffff6efee60 in __interceptor_malloc
/build/gcc-multilib/src/gcc/libsanitizer/asan/asan_malloc_linux.cc:62
    #1 0x7ffff686792f in bmalloc::Allocator::allocateSlowCase(unsigned
long)
(/home/g/Work/Code/webkit-master/WebKitBuild/Release/lib/libjavascriptcoregtk-4.0.so.18+0x214392f)

Thread T2 created by T0 here:
    #0 0x7ffff6e69498 in __interceptor_pthread_create
/build/gcc-multilib/src/gcc/libsanitizer/asan/asan_interceptors.cc:236
    #1 0x7ffff685b983 in WTF::createThreadInternal(void (*)(void*), void*,
char const*)
(/home/g/Work/Code/webkit-master/WebKitBuild/Release/lib/libjavascriptcoregtk-4.0.so.18+0x2137983)

SUMMARY: AddressSanitizer: heap-buffer-overflow
(/home/g/Work/Code/webkit-master/WebKitBuild/Release/lib/libjavascriptcoregtk-4.0.so.18+0x20cc4af)
in WTF::(anonymous namespace)::lockHashtable()
Shadow bytes around the buggy address:
  0x0c067fffa9a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c067fffa9b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c067fffa9c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c067fffa9d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c067fffa9e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c067fffa9f0: fa fa fa fa fa fa 00 00 00[00]fa fa fd fd fd fd
  0x0c067fffaa00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c067fffaa10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c067fffaa20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c067fffaa30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c067fffaa40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==24637==ABORTING

I'm forwarding this issue since i receive no answer from the Webkit
developers in more than 3 weeks. The original bug report (private) is here:

https://bugs.webkit.org/show_bug.cgi?id=164000

The reproducer are available upon request. Please assign a CVE if
necessary.

This issue was found using QuickFuzz.

Regards,
Gustavo.