https://github.com/python/cpython/commit/f1a93727c46cf9ae2df234c8667da8105a122388
commit: f1a93727c46cf9ae2df234c8667da8105a122388
branch: 3.13
author: Stan Ulbrych <[email protected]>
committer: vstinner <[email protected]>
date: 2025-11-06T16:16:43Z
summary:
[3.13] gh-140939: Fix memory leak in `_PyBytes_FormatEx` error path (GH-140957)
(#141155)
(cherry picked from commit d6c89a2df2c8b7603125883494e9058a88348f66)
files:
A Misc/NEWS.d/next/Core and
Builtins/2025-11-03-17-21-38.gh-issue-140939.FVboAw.rst
M Lib/test/test_bytes.py
M Objects/bytesobject.c
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index a3dec6bf96b730..c47fdd8f976d74 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -769,6 +769,13 @@ def __int__(self):
with self.assertRaisesRegex(TypeError, msg):
operator.mod(format_bytes, value)
+ def test_memory_leak_gh_140939(self):
+ # gh-140939: MemoryError is raised without leaking
+ _testcapi = import_helper.import_module('_testcapi')
+ with self.assertRaises(MemoryError):
+ b = self.type2test(b'%*b')
+ b % (_testcapi.PY_SSIZE_T_MAX, b'abc')
+
def test_imod(self):
b = self.type2test(b'hello, %b!')
orig = b
diff --git a/Misc/NEWS.d/next/Core and
Builtins/2025-11-03-17-21-38.gh-issue-140939.FVboAw.rst b/Misc/NEWS.d/next/Core
and Builtins/2025-11-03-17-21-38.gh-issue-140939.FVboAw.rst
new file mode 100644
index 00000000000000..a2921761f75556
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and
Builtins/2025-11-03-17-21-38.gh-issue-140939.FVboAw.rst
@@ -0,0 +1,2 @@
+Fix memory leak when :class:`bytearray` or :class:`bytes` is formated with the
+``%*b`` format with a large width that results in a :exc:`MemoryError`.
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index cebc27f618cba1..d891121589fd3e 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -965,8 +965,10 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t
format_len,
/* 2: size preallocated for %s */
if (alloc > 2) {
res = _PyBytesWriter_Prepare(&writer, res, alloc - 2);
- if (res == NULL)
+ if (res == NULL) {
+ Py_XDECREF(temp);
goto error;
+ }
}
#ifndef NDEBUG
char *before = res;
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