[3.15] gh-113318: Fix @getter and @setter in Argument Clinic (GH-155778)

[serhiy-storchaka]

(cherry picked from commit 915970c)

Co-authored-by: Serhiy Storchaka storchaka@gmail.com

• Issue: Argument Clinic: Better internal implementation for @getter and @setter #113318

[youknowone]

While this is unmerged, 3.15 still crashes on the deletions:

$ python -X faulthandler -c "import sys; del sys._getframe().f_trace_opcodes"
Windows fatal exception: access violation

Current thread 0x0000304c (most recent call first):
  File "<string>", line 1 in <module>

import ssl
c = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
c.check_hostname = False
c.verify_mode = ssl.CERT_NONE
s = c.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO())._sslobj
del s.context   # same for del s.owner and del s.session

Windows fatal exception: access violation

Current thread 0x000019f0 (most recent call first):
  File "s.py", line 6 in <module>

Objects/clinic/frameobject.c.h and Modules/clinic/_ssl.c.h have no
value == NULL without this patch

[hugovk]

@serhiy-storchaka Please could you get a core peer review on this?

[serhiy-storchaka]

@encukou, could you please review this?

@hugovk, this is an ordinary bug fix, it can wait for the next bugfix release.

[encukou]

LGTM, but it should go in 3.16.1.

(IMO it should not be treated as a security issue: we generally treat crashes as exploitable, but deleting arbitrary attributes is arbitrary code execution.)

[serhiy-storchaka]

The bug was not new in 3.15. It existed in 3.13 and 3=.14 (although 3.15 might add more cases). It does not affect working (and tested) programs, it cannot be triggered by user data.