Memory leak when parsing icon file

[guidovranken]

The following produces a memory leak:

    poc = bytes([0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x03, 0xaf, 0x10, 0x00, 0x01, 0x00,
      0x04, 0x00, 0xe8, 0x02, 0x00, 0x00, 0x16, 0x00, 0x00, 0x00, 0x28, 0x00,
      0x00, 0x00, 0x95, 0x00, 0x00, 0x00, 0x40, 0x00, 0x01, 0x00, 0x00, 0x00,
      0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x12, 0x0b,
      0x00, 0x00, 0x12, 0x0b, 0x00, 0x00, 0x00, 0x7a, 0x00, 0x00, 0x10, 0x00,
      0x00, 0x00, 0x00, 0x0b, 0x00, 0x00])
    p = ImageFile.Parser()
    try:
        p.feed(poc)
    except:
        pass

=================================================================
==10309==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 34 byte(s) in 1 object(s) allocated from:
    #0 0x54905d in malloc /src/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:145:3
    #1 0x580764 in _PyBytes_FromSize /src/cpython-3.8.1/Objects/bytesobject.c:86:31
    #2 0x580578 in PyBytes_FromStringAndSize /src/cpython-3.8.1/Objects/bytesobject.c:120:27
    #3 0x58eaa0 in bytes_subscript /src/cpython-3.8.1/Objects/bytesobject.c:1695:22
    #4 0x8f8a90 in PyObject_GetItem /src/cpython-3.8.1/Objects/abstract.c:154:26
    #5 0x7085be in _PyEval_EvalFrameDefault /src/cpython-3.8.1/Python/ceval.c:1607:29
    #6 0x59ce17 in function_code_fastcall /src/cpython-3.8.1/Objects/call.c:283:14
    #7 0x71b9ee in _PyObject_Vectorcall /src/cpython-3.8.1/./Include/cpython/abstract.h:127:11
    #8 0x7179ad in call_function /src/cpython-3.8.1/Python/ceval.c:5105:13
    #9 0x701f39 in _PyEval_EvalFrameDefault /src/cpython-3.8.1/Python/ceval.c:3597:23
    #10 0x719276 in _PyEval_EvalCodeWithName /src/cpython-3.8.1/Python/ceval.c:4416:14
    #11 0x59d279 in _PyFunction_Vectorcall /src/cpython-3.8.1/Objects/call.c:435:12
    #12 0x71b9ee in _PyObject_Vectorcall /src/cpython-3.8.1/./Include/cpython/abstract.h:127:11
    #13 0x7179ad in call_function /src/cpython-3.8.1/Python/ceval.c:5105:13
    #14 0x701f39 in _PyEval_EvalFrameDefault /src/cpython-3.8.1/Python/ceval.c:3597:23
    #15 0x59ce17 in function_code_fastcall /src/cpython-3.8.1/Objects/call.c:283:14
    #16 0x71b9ee in _PyObject_Vectorcall /src/cpython-3.8.1/./Include/cpython/abstract.h:127:11
    #17 0x7179ad in call_function /src/cpython-3.8.1/Python/ceval.c:5105:13
    #18 0x701f39 in _PyEval_EvalFrameDefault /src/cpython-3.8.1/Python/ceval.c:3597:23
    #19 0x59ce17 in function_code_fastcall /src/cpython-3.8.1/Objects/call.c:283:14
    #20 0x71b9ee in _PyObject_Vectorcall /src/cpython-3.8.1/./Include/cpython/abstract.h:127:11
    #21 0x7179ad in call_function /src/cpython-3.8.1/Python/ceval.c:5105:13
    #22 0x701f39 in _PyEval_EvalFrameDefault /src/cpython-3.8.1/Python/ceval.c:3597:23
    #23 0x719276 in _PyEval_EvalCodeWithName /src/cpython-3.8.1/Python/ceval.c:4416:14
    #24 0x59d279 in _PyFunction_Vectorcall /src/cpython-3.8.1/Objects/call.c:435:12
    #25 0x59ab40 in _PyObject_FastCallDict /src/cpython-3.8.1/Objects/call.c:96:15
    #26 0x59ec53 in _PyObject_Call_Prepend /src/cpython-3.8.1/Objects/call.c:887:14
    #27 0x64c7d9 in slot_tp_init /src/cpython-3.8.1/Objects/typeobject.c:6755:15
    #28 0x63d4a9 in type_call /src/cpython-3.8.1/Objects/typeobject.c:991:19
    #29 0x59afd1 in _PyObject_MakeTpCall /src/cpython-3.8.1/Objects/call.c:159:18

Initial analysis suggests this may be due to PyImaging_MapBuffer (reference increased but not decreased)?

[radarhere]

I've created PR #4381. Do you agree that it resolves this?