Bug 285393 – [JSC] heap-buffer-overflow on WebKit/Source/JavaScriptCore/runtime/WriteBarrier.h:166:17

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

Created attachment 473776 [details]
poc.js

1. Tested on Webkit branch main
2. Target release - crashes
3. Target debug - crashes
4. Run with `./bin/jsc ./poc.js`

# commit @main
```
commit b3809e07dc65e5678706c3ee334ca12930ebf129 (HEAD -> main, origin/main, origin/HEAD)
Author: Rob Buis <[e-mail]>
Date:   Sat Jan 4 12:19:18 2025 -0800
```

# Error stack release target
```
=================================================================
==437170==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x52d000023ff8 at pc 0x601974d9c81b bp 0x7fff5fcecb30 sp 0x7fff5fcecb28
WRITE of size 16 at 0x52d000023ff8 thread T0
    #0 0x601974d9c81a in JSC::WriteBarrierBase<JSC::Unknown, WTF::RawValueTraits<JSC::Unknown>>::setWithoutWriteBarrier(JSC::JSValue) /home/rheza/WebKit/Source/JavaScriptCore/runtime/WriteBarrier.h:166:17
    #1 0x601974d9c81a in JSC::ContiguousData<JSC::WriteBarrier<JSC::Unknown, WTF::RawValueTraits<JSC::Unknown>>>::Data::setWithoutWriteBarrier(JSC::JSValue const&) /home/rheza/WebKit/Source/JavaScriptCore/runtime/Butterfly.h:87:20
    #2 0x601974d9c81a in JSC::JSArray::fastFill(JSC::VM&, unsigned int, unsigned int, JSC::JSValue) /home/rheza/WebKit/Source/JavaScriptCore/runtime/JSArray.cpp:520:43
    #3 0x601974a2c8a7 in JSC::arrayProtoFuncFill(JSC::JSGlobalObject*, JSC::CallFrame*) /home/rheza/WebKit/Source/JavaScriptCore/runtime/ArrayPrototype.cpp:1946:20
    #4 0x7e9f7ca10037  (<unknown module>)

0x52d000024000 is located 0 bytes after 16384-byte region [0x52d000020000,0x52d000024000)
allocated by thread T0 here:
    #0 0x601972083606 in aligned_alloc (/home/rheza/WebKit/webkit-clang-main-release/bin/jsc+0xcf9606) (BuildId: 38bf8325b8192e73)
    #1 0x60197639e884 in pas_debug_heap_allocate(unsigned long, unsigned long, pas_allocation_mode) /home/rheza/WebKit/webkit-clang-main-release/bmalloc/Headers/bmalloc/pas_debug_heap.h:102:22
    #2 0x60197639bdd5 in bmalloc_try_allocate_with_alignment_impl(unsigned long, unsigned long, pas_allocation_mode) /home/rheza/WebKit/webkit-clang-main-release/bmalloc/Headers/bmalloc/bmalloc_heap_inlines.h:59:1
    #3 0x60197639bdd5 in bmalloc_try_allocate_with_alignment_inline(unsigned long, unsigned long, pas_allocation_mode) /home/rheza/WebKit/webkit-clang-main-release/bmalloc/Headers/bmalloc/bmalloc_heap_inlines.h:104:19
    #4 0x60197639bdd5 in bmalloc::api::tryMemalign(unsigned long, unsigned long, bmalloc::CompactAllocationMode, bmalloc::HeapKind) /home/rheza/WebKit/webkit-clang-main-release/bmalloc/Headers/bmalloc/bmalloc.h:124:16
    #5 0x60197639bdd5 in WTF::tryFastCompactAlignedMalloc(unsigned long, unsigned long) /home/rheza/WebKit/Source/WTF/wtf/FastMalloc.cpp:780:20
    #6 0x601973f4442e in JSC::LocalAllocator::allocate(JSC::Heap&, unsigned long, JSC::GCDeferralContext*, JSC::AllocationFailureMode)::'lambda'()::operator()() const /home/rheza/WebKit/Source/JavaScriptCore/heap/LocalAllocatorInlines.h:41:43
    #7 0x601973f4442e in JSC::HeapCell* JSC::FreeList::allocateWithCellSize<JSC::LocalAllocator::allocate(JSC::Heap&, unsigned long, JSC::GCDeferralContext*, JSC::AllocationFailureMode)::'lambda'()>(JSC::LocalAllocator::allocate(JSC::Heap&, unsigned long, JSC::GCDeferralContext*, JSC::AllocationFailureMode)::'lambda'() const&, unsigned long) /home/rheza/WebKit/Source/JavaScriptCore/heap/FreeListInlines.h:46:16
    #8 0x601973f4442e in JSC::LocalAllocator::allocate(JSC::Heap&, unsigned long, JSC::GCDeferralContext*, JSC::AllocationFailureMode) /home/rheza/WebKit/Source/JavaScriptCore/heap/LocalAllocatorInlines.h:38:23
    #9 0x601973f4442e in JSC::Allocator::allocate(JSC::Heap&, unsigned long, JSC::GCDeferralContext*, JSC::AllocationFailureMode) const /home/rheza/WebKit/Source/JavaScriptCore/heap/AllocatorInlines.h:35:30
    #10 0x601973f4442e in JSC::CompleteSubspace::tryAllocateSlow(JSC::VM&, unsigned long, JSC::GCDeferralContext*) /home/rheza/WebKit/Source/JavaScriptCore/heap/CompleteSubspace.cpp:122:26
    #11 0x601973f43d78 in JSC::CompleteSubspace::allocateSlow(JSC::VM&, unsigned long, JSC::GCDeferralContext*, JSC::AllocationFailureMode) /home/rheza/WebKit/Source/JavaScriptCore/heap/CompleteSubspace.cpp:108:20

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/rheza/WebKit/Source/JavaScriptCore/runtime/WriteBarrier.h:166:17 in JSC::WriteBarrierBase<JSC::Unknown, WTF::RawValueTraits<JSC::Unknown>>::setWithoutWriteBarrier(JSC::JSValue)
Shadow bytes around the buggy address:
  0x52d000023d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x52d000023d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x52d000023e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x52d000023e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x52d000023f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x52d000023f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00[00]
  0x52d000024000: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x52d000024080: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x52d000024100: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x52d000024180: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x52d000024200: 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
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  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
==437170==ABORTING
```

# Error stack on debug target

```
ASSERTION FAILED: index < m_length
/home/rheza/WebKit/Source/JavaScriptCore/runtime/ButterflyInlines.h(48) : typename ContiguousData<T>::Data JSC::ContiguousData<JSC::WriteBarrier<Unknown, RawValueTraits<Unknown>>>::at(const JSCell *, size_t) [T = JSC::WriteBarrier<Unknown, RawValueTraits<Unknown>>]
1   0x56ea78a0ff04 WTFReportBacktrace
2   0x56ea73fdb9b3 JSC::ContiguousData<JSC::WriteBarrier<JSC::Unknown, WTF::RawValueTraits<JSC::Unknown> > >::at(JSC::JSCell const*, unsigned long)
3   0x56ea7739a257 JSC::JSArray::fastFill(JSC::VM&, unsigned int, unsigned int, JSC::JSValue)
4   0x56ea76f813a1 JSC::arrayProtoFuncFill(JSC::JSGlobalObject*, JSC::CallFrame*)
5   0x7428dba10038 ???
Aborted (core dumped)
```

[Radar WebKit Bug Importer]

<rdar://problem/142369820>

[Yusuke Suzuki]

ToT crash.

[Yusuke Suzuki]

Pull request: https://github.com/WebKit/WebKit/pull/38698

[EWS]

Committed 288578@main (c702978087bc): <https://commits.webkit.org/288578@main>

Reviewed commits have been landed. Closing PR #38698 and removing active labels.