https://github.com/python/cpython/commit/4f8a77bf3fa8d0c10ddd50a8dda4ad89e8d2434e commit: 4f8a77bf3fa8d0c10ddd50a8dda4ad89e8d2434e branch: 3.14 author: Miss Islington (bot) <[email protected]> committer: gpshead <[email protected]> date: 2026-04-11T22:46:26Z summary:
[3.14] gh-145105: Fix crash in csv.reader with re-entrant iterator (GH-145106) (#148404) gh-145105: Fix crash in csv.reader with re-entrant iterator (GH-145106) When a custom iterator calls next() on the same csv.reader from within __next__, the inner iteration sets self->fields to NULL. The outer iteration then crashes in parse_save_field() by passing NULL to PyList_Append. Add a guard after PyIter_Next() to detect that fields was set to NULL by a re-entrant call, and raise csv.Error instead of crashing. (cherry picked from commit 20994b1809f9c162e4cae01a5af08bd492ede9f9) Co-authored-by: Ramin Farajpour Cami <[email protected]> files: A Misc/NEWS.d/next/Library/2026-02-22-00-00-00.gh-issue-145105.csv-reader-reentrant.rst M Lib/test/test_csv.py M Modules/_csv.c diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py index 98ee0c3cdd7a06..a0a1e91777d893 100644 --- a/Lib/test/test_csv.py +++ b/Lib/test/test_csv.py @@ -553,6 +553,33 @@ def test_roundtrip_escaped_unquoted_newlines(self): self.assertEqual(row, rows[i]) + def test_reader_reentrant_iterator(self): + # gh-145105: re-entering the reader from the iterator must not crash. + class ReentrantIter: + def __init__(self): + self.reader = None + self.n = 0 + def __iter__(self): + return self + def __next__(self): + self.n += 1 + if self.n == 1: + try: + next(self.reader) + except StopIteration: + pass + return "a,b" + if self.n == 2: + return "x" + raise StopIteration + + it = ReentrantIter() + reader = csv.reader(it) + it.reader = reader + with self.assertRaises(csv.Error): + next(reader) + + class TestDialectRegistry(unittest.TestCase): def test_registry_badargs(self): self.assertRaises(TypeError, csv.list_dialects, None) diff --git a/Misc/NEWS.d/next/Library/2026-02-22-00-00-00.gh-issue-145105.csv-reader-reentrant.rst b/Misc/NEWS.d/next/Library/2026-02-22-00-00-00.gh-issue-145105.csv-reader-reentrant.rst new file mode 100644 index 00000000000000..bc61cc43a5aa33 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-02-22-00-00-00.gh-issue-145105.csv-reader-reentrant.rst @@ -0,0 +1,2 @@ +Fix crash in :mod:`csv` reader when iterating with a re-entrant iterator +that calls :func:`next` on the same reader from within ``__next__``. diff --git a/Modules/_csv.c b/Modules/_csv.c index b994a42775178d..fd681f81a3b197 100644 --- a/Modules/_csv.c +++ b/Modules/_csv.c @@ -965,6 +965,12 @@ Reader_iternext_lock_held(PyObject *op) Py_DECREF(lineobj); return NULL; } + if (self->fields == NULL) { + PyErr_SetString(module_state->error_obj, + "iterator has already advanced the reader"); + Py_DECREF(lineobj); + return NULL; + } ++self->line_num; kind = PyUnicode_KIND(lineobj); data = PyUnicode_DATA(lineobj); _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
