Segfault in _testinternalcapi.assemble_code_object with LOAD_CLOSURE

Bug report

Bug description:

import _testinternalcapi

# The crash is triggered by the 'LOAD_CLOSURE' pseudo-instruction
# when passed to the internal code object assembler.
instructions = [
    ('RESUME', 0),
    ('LOAD_CLOSURE', 0),  # The trigger: oparg 0 refers to index in cellvars
    ('RETURN_VALUE', None)
]

# Metadata setup to support the instructions
metadata = {
    'filename': 'crash.py',
    'name': 'crash_test',
    'consts': {None: 0},
    'cellvars': {'x': 0},  # 'x' is at index 0
    'varnames': {'x': 0},  # 'x' is also defined as a local var
    'argcount': 1,
    'posonlyargcount': 0,
    'kwonlyargcount': 0
}

print("Attempting to assemble code object...")
# This call segfaults
_testinternalcapi.assemble_code_object('crash.py', instructions, metadata)

Attempting to assemble code object...
AddressSanitizer:DEADLYSIGNAL
=================================================================
==775815==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 0x7309e1b4b3f9 bp 0x7fffa1d84300 sp 0x7fffa1d84240 T0)
==775815==The signal is caused by a READ memory access.
==775815==Hint: address points to the zero page.
    #0 0x7309e1b4b3f9 in PyType_HasFeature /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Include/object.h:824:19
    #1 0x7309e1b4b3f9 in _testinternalcapi_assemble_code_object_impl /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Modules/_testinternalcapi.c:840:5
    #2 0x7309e1b4b3f9 in _testinternalcapi_assemble_code_object /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Modules/clinic/_testinternalcapi.c.h:293:20
    #3 0x56088dcc075b in cfunction_vectorcall_FASTCALL_KEYWORDS /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Objects/methodobject.c:465:24
    #4 0x56088dba135f in _PyObject_VectorcallTstate /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Include/internal/pycore_call.h:136:11
    #5 0x56088df3451c in _Py_VectorCallInstrumentation_StackRefSteal /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Python/ceval.c:762:11
    #6 0x56088df70350 in _PyEval_EvalFrameDefault /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Python/generated_cases.c.h:1788:35
    #7 0x56088df333b7 in _PyEval_EvalFrame /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Include/internal/pycore_ceval.h:118:16
    #8 0x56088df333b7 in _PyEval_Vector /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Python/ceval.c:2094:12
    #9 0x56088df32dd4 in PyEval_EvalCode /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Python/ceval.c:673:21
    #10 0x56088e57d46e in run_eval_code_obj /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Python/pythonrun.c:1366:12
    #11 0x56088e57c63b in run_mod /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Python/pythonrun.c:1469:19
    #12 0x56088e576c3c in pyrun_file /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Python/pythonrun.c:1294:15
    #13 0x56088e57479c in _PyRun_SimpleFileObject /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Python/pythonrun.c:518:13
    #14 0x56088e573b0d in _PyRun_AnyFileObject /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Python/pythonrun.c:81:15
    #15 0x56088e5f03ba in pymain_run_file_obj /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Modules/main.c:410:15
    #16 0x56088e5f03ba in pymain_run_file /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Modules/main.c:429:15
    #17 0x56088e5ee483 in pymain_run_python /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Modules/main.c:691:21
    #18 0x56088e5ee483 in Py_RunMain /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Modules/main.c:772:5
    #19 0x56088e5ef386 in pymain_main /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Modules/main.c:802:12
    #20 0x56088e5ef4f7 in Py_BytesMain /home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/../Modules/main.c:826:12
    #21 0x7709e2b02d8f in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #22 0x7709e2b02e3f in __libc_start_main csu/../csu/libc-start.c:392:3
    #23 0x56088d8f74c4 in _start (/home/fuzz/WorkSpace/FusionFuzzLoop/projects/cpython/cpython/build/python+0x2e44c4) (BuildId: d529462274be082e41d89921c4fd912eb8eb1797)

==775815==Register values:
rax = 0x0000000000000008  rbx = 0x00007fffa1d84240  rcx = 0x0000000000000001  rdx = 0x00000ac111dad84d  
rdi = 0x00000000000000a8  rsi = 0x0000000000000000  rbp = 0x00007fffa1d84300  rsp = 0x00007fffa1d84240  
 r8 = 0x00000ee13c55b005   r9 = 0xffffffffffffffe8  r10 = 0x00000ac111dad838  r11 = 0x0000000000000001  
r12 = 0x00007309e0904d20  r13 = 0x00007389e1c90740  r14 = 0x00000e613c1209a0  r15 = 0x00007309e0904c28  
AddressSanitizer can not provide additional info.

Could be a low-priority bug.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Bắt đầu với Modules/_testinternalcapi.c tại _testinternalcapi_assemble_code_object_impl, được xác định bởi sanitizer trace. Chạy reproducer LOAD_CLOSURE được cung cấp dưới AddressSanitizer và theo dõi cách metadata của cellvars và varnames được xử lý. Công việc được hoàn tất khi input không còn gây ra segmentation fault và hành vi này được bao phủ bởi một regression test.