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gh-123083: Fix a potential use-after-free in STORE_ATTR_WITH_HINT #123092

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Merged
merged 4 commits into from
Aug 22, 2024
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gh-123083: Fix a potential use-after-free in STORE_ATTR_WITH_HINT #123092

merged 4 commits into from
Aug 22, 2024
+42 −18

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corona10
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@corona10 corona10 commented Aug 17, 2024 •
edited by bedevere-app bot
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@corona10 corona10 requested a review from markshannon as a code owner August 17, 2024 08:27
@bedevere-app bedevere-app bot mentioned this pull request Aug 17, 2024
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@corona10 corona10 added needs backport to 3.12 only security fixes needs backport to 3.13 bugs and security fixes labels Aug 17, 2024
corona10
corona10 commented Aug 17, 2024
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Lib/test/test_dict.py
@@ -1476,6 +1476,24 @@ def test_dict_items_result_gc_reversed(self):
gc.collect()
self.assertTrue(gc.is_tracked(next(it)))

def test_store_evilattr(self):
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I am not sure that this is the proper place.

@corona10 corona10 added the 🔨 test-with-refleak-buildbots Test PR w/ refleak buildbots; report in status section label Aug 17, 2024
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🤖 New build scheduled with the buildbot fleet by @corona10 for commit 6cdacd8 🤖

If you want to schedule another build, you need to add the 🔨 test-with-refleak-buildbots label again.

@bedevere-bot bedevere-bot removed the 🔨 test-with-refleak-buildbots Test PR w/ refleak buildbots; report in status section label Aug 17, 2024
@corona10 corona10 changed the title gh-123083: Fix STORE_ATTR_WITH_HINT has potential use-after-free gh-123083: Fix a potential use-after-free in STORE_ATTR_WITH_HINT Aug 17, 2024
@corona10 corona10 added the 🔨 test-with-refleak-buildbots Test PR w/ refleak buildbots; report in status section label Aug 17, 2024
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🤖 New build scheduled with the buildbot fleet by @corona10 for commit a71d20d 🤖

If you want to schedule another build, you need to add the 🔨 test-with-refleak-buildbots label again.

@bedevere-bot bedevere-bot removed the 🔨 test-with-refleak-buildbots Test PR w/ refleak buildbots; report in status section label Aug 17, 2024
colesbury
colesbury reviewed Aug 19, 2024
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Python/bytecodes.c Outdated
@@ -2234,12 +2234,12 @@ dummy_func(
PyDict_WatchEvent event = old_value == NULL ? PyDict_EVENT_ADDED : PyDict_EVENT_MODIFIED;
new_version = _PyDict_NotifyEvent(tstate->interp, event, dict, name, PyStackRef_AsPyObjectBorrow(value));
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I think we should structure this to match the ordering in dictobject.c:

cpython/Objects/dictobject.c

Lines 1693 to 1707 in b6d0a40

MAINTAIN_TRACKING(mp, key, value);
PyObject *old_value = mp->ma_values->values[ix];
if (old_value == NULL) {
uint64_t new_version = _PyDict_NotifyEvent(interp, PyDict_EVENT_ADDED, mp, key, value);
STORE_SPLIT_VALUE(mp, ix, Py_NewRef(value));
_PyDictValues_AddToInsertionOrder(mp->ma_values, ix);
STORE_USED(mp, mp->ma_used + 1);
mp->ma_version_tag = new_version;
}
else {
uint64_t new_version = _PyDict_NotifyEvent(interp, PyDict_EVENT_MODIFIED, mp, key, value);
STORE_SPLIT_VALUE(mp, ix, Py_NewRef(value));
mp->ma_version_tag = new_version;
Py_DECREF(old_value);
}

  1. Update GC tracking if necessary
  2. Notify event
  3. Store value and version tag
  4. Decref old value

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Could you add a comment, specifically why this is the correct order?
It isn't obvious and it will be easy to reintroduce the error without some warning not to.

@corona10 corona10 requested a review from methane as a code owner August 20, 2024 15:28
@corona10 corona10 requested a review from colesbury August 20, 2024 15:30
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Thank you for the kind review!
I followed the suggestions. Please take a look. :)

@corona10
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@colesbury @markshannon gentle ping :)

markshannon
markshannon approved these changes Aug 22, 2024
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This looks fine to me. But let @colesbury review it before merging.

colesbury
colesbury approved these changes Aug 22, 2024
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LGTM too

@corona10 corona10 merged commit 297f2e0 into python:main Aug 22, 2024
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Thanks @corona10 for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12, 3.13.
🐍🍒⛏🤖

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Sorry, @corona10, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 297f2e093ec95800ae2184330b8408c875523467 3.13

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Sorry, @corona10, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 297f2e093ec95800ae2184330b8408c875523467 3.12

corona10 added a commit to corona10/cpython that referenced this pull request Aug 22, 2024
@corona10
[3.13] pythongh-123083: Fix a potential use-after-free in ``STORE_ATT…
0ab4e42 
…R_WITH_HINT`` (pythongh-123092)

(cherry picked from commit 297f2e0)

Co-authored-by: Donghee Na <donghee.na@python.org>
corona10 added a commit to corona10/cpython that referenced this pull request Aug 22, 2024
@corona10
[3.13] pythongh-123083: Fix a potential use-after-free in ``STORE_ATT…
1c16bdf 
…R_WITH_HINT`` (pythongh-123092)

(cherry picked from commit 297f2e0)

Co-authored-by: Donghee Na <donghee.na@python.org>
@corona10 corona10 mentioned this pull request Aug 22, 2024
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bedevere-app bot commented Aug 22, 2024

GH-123235 is a backport of this pull request to the 3.13 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.13 bugs and security fixes label Aug 22, 2024
@corona10 corona10 mentioned this pull request Aug 22, 2024
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bedevere-app bot commented Aug 22, 2024

GH-123237 is a backport of this pull request to the 3.12 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.12 only security fixes label Aug 22, 2024
corona10 added a commit that referenced this pull request Aug 22, 2024
@corona10
[3.13] gh-123083: Fix a potential use-after-free in ``STORE_ATTR_WITH… (
6cd67e4 
#123235)

[3.13] gh-123083: Fix a potential use-after-free in ``STORE_ATTR_WITH_HINT`` (gh-123092)
(cherry picked from commit 297f2e0)
corona10 added a commit that referenced this pull request Aug 22, 2024
@corona10
[3.12] gh-123083: Fix a potential use-after-free in ``STORE_ATTR_WITH… (
6e68559 
#123237)

[3.12] gh-123083: Fix a potential use-after-free in ``STORE_ATTR_WITH_HINT`` (gh-123092)
(cherry picked from commit 297f2e0)
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