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gh-92036: Fix gc_fini_untrack() (#92037)

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Fix a crash in subinterpreters related to the garbage collector. When
a subinterpreter is deleted, untrack all objects tracked by its GC.
To prevent a crash in deallocator functions expecting objects to be
tracked by the GC, leak a strong reference to these objects on
purpose, so they are never deleted and their deallocator functions
are not called.
This commit is contained in:
Victor Stinner 2022-05-04 11:59:01 +02:00 • committed by GitHub
parent d20bb33f78
commit 14243369b5
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5
Misc/NEWS.d/next/Core and Builtins/2022-04-28-23-37-30.gh-issue-92036.GZJAC9.rst Normal file
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@ -0,0 +1,5 @@
Fix a crash in subinterpreters related to the garbage collector. When a
subinterpreter is deleted, untrack all objects tracked by its GC. To prevent a
crash in deallocator functions expecting objects to be tracked by the GC, leak
a strong reference to these objects on purpose, so they are never deleted and
their deallocator functions are not called. Patch by Victor Stinner.

6
Modules/gcmodule.c
View file

@ -2165,6 +2165,12 @@ gc_fini_untrack(PyGC_Head *list)
for (gc = GC_NEXT(list); gc != list; gc = GC_NEXT(list)) {
PyObject *op = FROM_GC(gc);
_PyObject_GC_UNTRACK(op);
// gh-92036: If a deallocator function expect the object to be tracked
// by the GC (ex: func_dealloc()), it can crash if called on an object
// which is no longer tracked by the GC. Leak one strong reference on
// purpose so the object is never deleted and its deallocator is not
// called.
Py_INCREF(op);
}
}