From 74007fd03c391efdd7df71d04a123eb44867a978 Mon Sep 17 00:00:00 2001 From: Tobias Holl Date: Wed, 13 Jan 2021 17:16:40 +0100 Subject: [PATCH] bpo-42924: Fix incorrect copy in bytearray_repeat (GH-24208) Before, using the * operator to repeat a bytearray would copy data from the start of the internal buffer (ob_bytes) and not from the start of the actual data (ob_start). (cherry picked from commit 61d8c54f43a7871d016f98b38f86858817d927d5) Co-authored-by: Tobias Holl --- Lib/test/test_bytes.py | 10 ++++++++++ .../2021-01-13-14-06-01.bpo-42924._WS1Ok.rst | 1 + Objects/bytearrayobject.c | 6 ++++-- 3 files changed, 15 insertions(+), 2 deletions(-) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2021-01-13-14-06-01.bpo-42924._WS1Ok.rst diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py index bbd45c75298e72..c2ec1201e8d6bc 100644 --- a/Lib/test/test_bytes.py +++ b/Lib/test/test_bytes.py @@ -1592,6 +1592,16 @@ def test_iterator_length_hint(self): # Shouldn't raise an error self.assertEqual(list(it), []) + def test_repeat_after_setslice(self): + # bpo-42924: * used to copy from the wrong memory location + b = bytearray(b'abc') + b[:2] = b'x' + b1 = b * 1 + b3 = b * 3 + self.assertEqual(b1, b'xc') + self.assertEqual(b1, b) + self.assertEqual(b3, b'xcxcxc') + class AssortedBytesTest(unittest.TestCase): # diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-01-13-14-06-01.bpo-42924._WS1Ok.rst b/Misc/NEWS.d/next/Core and Builtins/2021-01-13-14-06-01.bpo-42924._WS1Ok.rst new file mode 100644 index 00000000000000..33fbb5235ddb66 --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2021-01-13-14-06-01.bpo-42924._WS1Ok.rst @@ -0,0 +1 @@ +Fix ``bytearray`` repetition incorrectly copying data from the start of the buffer, even if the data is offset within the buffer (e.g. after reassigning a slice at the start of the ``bytearray`` to a shorter byte string). diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c index d4d02336b6cf03..9812afd6f2c34e 100644 --- a/Objects/bytearrayobject.c +++ b/Objects/bytearrayobject.c @@ -332,6 +332,7 @@ bytearray_repeat(PyByteArrayObject *self, Py_ssize_t count) PyByteArrayObject *result; Py_ssize_t mysize; Py_ssize_t size; + const char *buf; if (count < 0) count = 0; @@ -340,13 +341,14 @@ bytearray_repeat(PyByteArrayObject *self, Py_ssize_t count) return PyErr_NoMemory(); size = mysize * count; result = (PyByteArrayObject *)PyByteArray_FromStringAndSize(NULL, size); + buf = PyByteArray_AS_STRING(self); if (result != NULL && size != 0) { if (mysize == 1) - memset(result->ob_bytes, self->ob_bytes[0], size); + memset(result->ob_bytes, buf[0], size); else { Py_ssize_t i; for (i = 0; i < count; i++) - memcpy(result->ob_bytes + i*mysize, self->ob_bytes, mysize); + memcpy(result->ob_bytes + i*mysize, buf, mysize); } } return (PyObject *)result;