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Add PyExc_OverflowError to the list of possible exceptions in fuzz_ast_literal_eval fuzzer#145429

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encukou merged 1 commit intopython:mainfrom
StanFromIreland:fix-fuzz_ast_literal_eval
Mar 3, 2026
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Add PyExc_OverflowError to the list of possible exceptions in fuzz_ast_literal_eval fuzzer#145429
encukou merged 1 commit intopython:mainfrom
StanFromIreland:fix-fuzz_ast_literal_eval

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@StanFromIreland StanFromIreland commented Mar 2, 2026

This fixes the "bug" found in https://oss-fuzz.com/testcase-detail/5450638250278912.

>>> import ast
... data = open('/tmp/testcase', 'rb').read()
... ast.literal_eval(data[:data.index(0)].decode())
... 
<python-input-2>:2: ResourceWarning: unclosed file <_io.BufferedReader name='/tmp/testcase'>
ResourceWarning: Enable tracemalloc to get the object allocation traceback
Traceback (most recent call last):
  File "<python-input-2>", line 3, in <module>
    ast.literal_eval(data[:data.index(0)].decode())
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/stan/dev/cpython/Lib/ast.py", line 64, in literal_eval
    return _convert_literal(node_or_string)
  File "/home/stan/dev/cpython/Lib/ast.py", line 108, in _convert_literal
    return left + right
           ~~~~~^~~~~~~
OverflowError: int too large to convert to float
With fuzzer

Currently:

$ ./python -c "
import _xxtestfuzz
data = open('/tmp/testcase', 'rb').read()
_xxtestfuzz.run(data)
"
<string>:3: ResourceWarning: unclosed file <_io.BufferedReader name='/tmp/testcase'>
ResourceWarning: Enable tracemalloc to get the object allocation traceback
Traceback (most recent call last):
  File "/home/stan/dev/cpython/Lib/ast.py", line 64, in literal_eval
    return _convert_literal(node_or_string)
  File "/home/stan/dev/cpython/Lib/ast.py", line 108, in _convert_literal
    return left + right
           ~~~~~^~~~~~~
OverflowError: int too large to convert to float
Aborted (core dumped)

With fix:

$ ./python -c "
import _xxtestfuzz
data = open('/tmp/testcase', 'rb').read()
_xxtestfuzz.run(data)
"
<string>:3: ResourceWarning: unclosed file <_io.BufferedReader name='/tmp/testcase'>
ResourceWarning: Enable tracemalloc to get the object allocation traceback

@StanFromIreland StanFromIreland added tests Tests in the Lib/test dir skip issue skip news labels Mar 2, 2026
ammaraskar
ammaraskar approved these changes Mar 2, 2026
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Looks good to ignore this, we don't particularly care about overflow here.

@encukou encukou merged commit a929e80 into python:main Mar 3, 2026
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@StanFromIreland StanFromIreland deleted the fix-fuzz_ast_literal_eval branch March 3, 2026 13:20
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@ammaraskar ammaraskar ammaraskar approved these changes

@gpshead gpshead Awaiting requested review from gpshead

@sethmlarson sethmlarson Awaiting requested review from sethmlarson

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@StanFromIreland @ammaraskar @encukou