gh-151815: Fix segfault in template_iter on allocation failure#151821
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Pull request overview
Fixes a crash in the C implementation of t-string Template iteration by making the iterator object safe to deallocate when construction fails partway through (e.g., on PyObject_GetIter() allocation failure).
Changes:
- Initialize
templateiterobject’sstringsiterandinterpolationsitertoNULLimmediately afterPyObject_GC_New()sotp_clear/Py_CLEARis safe on error paths. - Add a NEWS blurb documenting the crash fix.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
Objects/templateobject.c |
Prevents segfault by NULL-initializing iterator fields before any fallible operations. |
Misc/NEWS.d/next/Core_and_Builtins/2026-06-20-14-00-00.gh-issue-151815.TmplIt.rst |
Documents the crash fix in the Core and Builtins NEWS entries. |
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| template_iter(PyObject *op) | ||
| { | ||
| templateobject *self = templateobject_CAST(op); | ||
| templateiterobject *iter = PyObject_GC_New(templateiterobject, &_PyTemplateIter_Type); | ||
| if (iter == NULL) { | ||
| return NULL; | ||
| } | ||
| iter->stringsiter = NULL; | ||
| iter->interpolationsiter = NULL; |
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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool. If this change has little impact on Python users, wait for a maintainer to apply the |
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template_iter()allocates atemplateiterobjectwithPyObject_GC_New(which does not zero memory), but only assignsstringsiterandinterpolationsiterafter bothPyObject_GetItercalls succeed. If either call fails,Py_DECREF(iter)runstemplateiter_clear, which callsPy_CLEARon uninitialized pointers, causing a segfault.Fix: initialize both fields to
NULLimmediately after allocation soPy_CLEARis safe on the error paths.