New submission from CendioOssman <oss...@cendio.se>:
A python equivalent of the classical daemon() call started throwing an error
from 3.8 when the debug hooks are active for pymalloc. If the tracing is also
active it segfaults.
This simple example triggers it:
import os
def daemon():
pid = os.fork()
if pid != 0:
os._exit(0)
daemon()
The error given is:
Debug memory block at address p=0xf013d0: API '1'
0 bytes originally requested
The 7 pad bytes at p-7 are not all FORBIDDENBYTE (0xfd):
at p-7: 0x00 *** OUCH
at p-6: 0x00 *** OUCH
at p-5: 0x00 *** OUCH
at p-4: 0x00 *** OUCH
at p-3: 0x00 *** OUCH
at p-2: 0x00 *** OUCH
at p-1: 0x00 *** OUCH
Because memory is corrupted at the start, the count of bytes requested
may be bogus, and checking the trailing pad bytes may segfault.
The 8 pad bytes at tail=0xf013d0 are not all FORBIDDENBYTE (0xfd):
at tail+0: 0x01 *** OUCH
at tail+1: 0x00 *** OUCH
at tail+2: 0x00 *** OUCH
at tail+3: 0x00 *** OUCH
at tail+4: 0x00 *** OUCH
at tail+5: 0x00 *** OUCH
at tail+6: 0x00 *** OUCH
at tail+7: 0x00 *** OUCH
Enable tracemalloc to get the memory block allocation traceback
Fatal Python error: bad ID: Allocated using API '1', verified using API 'r'
Python runtime state: finalizing (tstate=0xf023b0)
Tested on Fedora, Ubuntu and RHEL with the same behaviour everwhere. Everything
up to 3.8 works fine. 3.8 and 3.9 both exhibit the issue.
Since this is a very standard way of starting a daemon it should affect quite a
few users. At the very least it makes it annoying to use development mode to
catch other issues.
----------
components: Interpreter Core
messages: 382314
nosy: CendioOssman
priority: normal
severity: normal
status: open
title: Debug pymalloc crash when using os.fork() [regression]
type: crash
versions: Python 3.10, Python 3.8, Python 3.9
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue42540>
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