New submission from STINNER Victor:
Python implements debug hooks on Python memory allocators:
https://docs.python.org/dev/c-api/memory.html#c.PyMem_SetupDebugHooks
Problem: buffer understand and buffer overflow are only detected when a memory
block is released, which may occur far from the code responsible to create the
buffer.
Attached patch dumps the traceback where a memory block was allocated on error
in malloc debug hooks. The feature requires to enable tracemalloc to record
tracebacks.
test.py used in below example:
----
import _testcapi
def f():
_testcapi.pymem_buffer_overflow()
f()
----
Example:
---
haypo@selma$ ./python -X tracemalloc=5 test.py
Debug memory block at address p=0x22e8be0: API 'm'
16 bytes originally requested
The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.
The 8 pad bytes at tail=0x22e8bf0 are not all FORBIDDENBYTE (0xfb):
at tail+0: 0x78 *** OUCH
...
The block was made by call #37240 to debug malloc/realloc.
Data at p: cb cb cb cb cb cb cb cb cb cb cb cb cb cb cb cb
Memory block traceback (most recent call first):
File "test.py", line 4
File "test.py", line 6
Fatal Python error: bad trailing pad byte
Current thread 0x00007f4a93d9c700 (most recent call first):
File "test.py", line 4 in f
File "test.py", line 6 in <module>
Abandon (core dumped)
---
The patch adds the "Memory block traceback" section.
----------
files: pymem_tb.patch
keywords: patch
messages: 261793
nosy: haypo
priority: normal
severity: normal
status: open
title: Malloc debug hooks: display memory block traceback on error
type: enhancement
versions: Python 3.6
Added file: http://bugs.python.org/file42167/pymem_tb.patch
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue26564>
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