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GeezerVison is showing github.com — [backport to 3.5] bpo-29438: Fixed use-after-free in key sharing dict by methane · Pull Request #40 · python/cpython

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@methane

@methane methane commented Feb 12, 2017

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@methane
bpo-29438: Fixed use-after-free in key sharing dict
af40edf
@methane methane added the type-bug An unexpected behavior, bug, or error label Feb 12, 2017
@the-knights-who-say-ni the-knights-who-say-ni added the CLA signed label Feb 12, 2017
@methane methane changed the title bpo-29438: Fixed use-after-free in key sharing dict [backport to 3.5] bpo-29438: Fixed use-after-free in key sharing dict Feb 12, 2017
serhiy-storchaka
serhiy-storchaka reviewed Feb 12, 2017
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Comment thread Objects/dictobject.c
}
if (value == NULL) {
res = PyDict_DelItem(dict, key);
if (cached != ((PyDictObject *)dict)->ma_keys) {

@serhiy-storchaka serhiy-storchaka Feb 12, 2017

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@methane methane Feb 12, 2017

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In Python 3.5, PyDict_DelItem won't resize dict. So cached == dict->ma_keys in most cases.

One exception is callback called by weakref or __del__ inserts some items to the dict and resize happened.
In this case, cached != CACHED_KEYS(tp), so DK_DECREF(cached) will be "use-after-free".

In such case, the insertion from the callback would update CACHED_KEYS(tp) correctly.
So clearing CACHED_KEYS(tp) doesn't make sense for most case.

Even when the callback inserts items through __dict__ (not regular attribute access), skipping CACHED_KEYS(tp) = NULL
doesn't cause uncontrolled memory growth. And it happens very rarely.
So I think this code is not worth enough.

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serhiy-storchaka
serhiy-storchaka approved these changes Feb 12, 2017
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@methane
methane merged commit 06a4fcb into python:3.5 Feb 13, 2017
@methane
methane deleted the bpo29438/py35 branch February 13, 2017 00:16
@Mariatta Mariatta added the cherry-pick for 3.5 label Feb 14, 2017
@ziegenbalg ziegenbalg mentioned this pull request Nov 30, 2022
double free in io.TextIOWrapper #72573
Closed
jaraco pushed a commit that referenced this pull request Dec 2, 2022
@Mariatta
Use cherry-picker v 0.2.5 (GH-40)
e954502
oraluben pushed a commit to oraluben/cpython that referenced this pull request Jun 25, 2023
@Fidget-Spinner
fix: add multiple jump target to metadata, special ops can be jump ta…
426daf1 
…rgets (python#40)
@gvanrossum gvanrossum mentioned this pull request Aug 22, 2023
heap-use-after-free in _PyFunction_LookupByVersion #108253
Closed
@LinanV LinanV mentioned this pull request Oct 23, 2023
Objects/typeobject.c: No such file or directory. #111203
Closed
@kcatss kcatss mentioned this pull request Feb 20, 2024
Use After Free at _heapreplace_max #115706
Closed
@ngoldbaum ngoldbaum mentioned this pull request Sep 23, 2024
Crash running PyO3 tests with --test-threads=1000 #124375
Closed
This was referenced Feb 11, 2025
segmentfault when pip installing setuptools #129992
Closed
segmentfault when pip installing setuptools #129993
Closed
@DominiquePACCO DominiquePACCO mentioned this pull request Jun 3, 2025
PdfWriter add_page adds (re)writes old page instead of new #135062
Closed
@sergey-miryanov sergey-miryanov mentioned this pull request Dec 18, 2025
Observed memory leak in ssl library: Python 3.14 GC issue #142516
Closed
johnslavik pushed a commit to johnslavik/cpython that referenced this pull request Dec 19, 2025
@DinoV
Merge pull request python#40 from hugovk/3.15-lazy-rm-get_lazy_modules
b437afb 
Remove `get_lazy_modules` from docs
@ngoldbaum ngoldbaum mentioned this pull request Mar 6, 2026
Remove deprecated and undocumented function ctypes.SetPointerType #133866
Closed
SonicField added a commit to SonicField/cpython that referenced this pull request Apr 15, 2026
@SonicField
Add bytecode_offset=-1 self-enforcing invariant + regression test
13f3720 
Move bytecode_offset=-1 initialization into hir_c_alloc_instr so the
invariant is structurally enforced — even if hir_c_init_instr is
accidentally skipped, bytecode_offset will be -1 (not 0 from calloc).

Add runtime regression test in hir_instr_c_verify.cpp that verifies
the invariant for all three allocation paths (raw alloc, init_instr,
init_deopt). Runs at startup via __attribute__((constructor)).

Addresses gap flagged 5 times (Pythia python#14, python#40, python#59, librarian x2).
@johng johng mentioned this pull request Jul 19, 2026
use-after-free: functools partial #154189
Closed
@djarfluka djarfluka mentioned this pull request Sep 12, 2026
Heap UAF in io.TextIOWrapper read path via reentrant detach() #157363
Open
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@serhiy-storchaka serhiy-storchaka serhiy-storchaka approved these changes

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4 participants

@methane @serhiy-storchaka @Mariatta @the-knights-who-say-ni
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