[Python] `BufferReader.readinto()` segfaults on a read-only destination

[marinelay]

Summary

BufferReader.readinto() terminates the interpreter when its destination is a read-only buffer, including bytes and read-only memoryview objects.
I found this while fuzzing Python C extension modules.
I would expect a read-only destination to be rejected with TypeError or BufferError rather than causing a process crash.

Versions

PyArrow 25.0.1, CPython 3.12.3, Debian 12 x86_64, glibc 2.36

Reproducer

import pyarrow as pa

pa.BufferReader(b"x").readinto(b"a")

Segmentation fault (core dumped)

UBSan result

I built PyArrow 25.0.0 from source with Clang 18 using UBSan instrumentation.
UBSan reports that BufferReader.readinto() passes a null destination pointer to memcpy():

cpp/src/arrow/io/memory.cc:343:12: runtime error:
null pointer passed as argument 1, which is declared to never be null
/usr/include/string.h:44:28: note: nonnull attribute specified here

    #0 arrow::io::BufferReader::DoReadAt(...)
       cpp/src/arrow/io/memory.cc:343:5
    #1 arrow::io::BufferReader::DoRead(...)
       cpp/src/arrow/io/memory.cc:373:3
    #2 arrow::io::internal::RandomAccessFileConcurrencyWrapper<
           arrow::io::BufferReader>::Read(...)
       cpp/src/arrow/io/concurrency.h:181:23
    #3 pyarrow.lib.NativeFile.readinto(...)
       build/lib.cpp:244518:86

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
cpp/src/arrow/io/memory.cc:343:12

Component(s)

Python

[carrerasdarren-cell]

take

[raulcd]

Issue resolved by pull request 51126
#51126