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[3.9] bpo-43260: io: Prevent large data remains in textio buffer. (GH-24592) #24617

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Merged
merged 1 commit into from
Feb 22, 2021
Merged

[3.9] bpo-43260: io: Prevent large data remains in textio buffer. (GH-24592) #24617

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27 changes: 27 additions & 0 deletions Lib/test/test_io.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3747,6 +3747,33 @@ def test_del__CHUNK_SIZE_SystemError(self):
with self.assertRaises(AttributeError):
del t._CHUNK_SIZE

def test_internal_buffer_size(self):
# bpo-43260: TextIOWrapper's internal buffer should not store
# data larger than chunk size.
chunk_size = 8192 # default chunk size, updated later

class MockIO(self.MockRawIO):
def write(self, data):
if len(data) > chunk_size:
raise RuntimeError
return super().write(data)

buf = MockIO()
t = self.TextIOWrapper(buf, encoding="ascii")
chunk_size = t._CHUNK_SIZE
t.write("abc")
t.write("def")
# default chunk size is 8192 bytes so t don't write data to buf.
self.assertEqual([], buf._write_stack)

with self.assertRaises(RuntimeError):
t.write("x"*(chunk_size+1))

self.assertEqual([b"abcdef"], buf._write_stack)
t.write("ghi")
t.write("x"*chunk_size)
self.assertEqual([b"abcdef", b"ghi", b"x"*chunk_size], buf._write_stack)


class PyTextIOWrapperTest(TextIOWrapperTest):
io = pyio
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2021-02-20-12-15-29.bpo-43260.6znAas.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix TextIOWrapper can not flush internal buffer forever after very large
text is written.
20 changes: 17 additions & 3 deletions Modules/_io/textio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1602,6 +1602,8 @@ _textiowrapper_writeflush(textio *self)
ret = PyObject_CallMethodOneArg(self->buffer, _PyIO_str_write, b);
} while (ret == NULL && _PyIO_trap_eintr());
Py_DECREF(b);
// NOTE: We cleared buffer but we don't know how many bytes are actually written
// when an error occurred.
if (ret == NULL)
return -1;
Py_DECREF(ret);
Expand Down Expand Up @@ -1659,7 +1661,10 @@ _io_TextIOWrapper_write_impl(textio *self, PyObject *text)

/* XXX What if we were just reading? */
if (self->encodefunc != NULL) {
if (PyUnicode_IS_ASCII(text) && is_asciicompat_encoding(self->encodefunc)) {
if (PyUnicode_IS_ASCII(text) &&
// See bpo-43260
PyUnicode_GET_LENGTH(text) <= self->chunk_size &&
is_asciicompat_encoding(self->encodefunc)) {
b = text;
Py_INCREF(b);
}
Expand All @@ -1668,8 +1673,9 @@ _io_TextIOWrapper_write_impl(textio *self, PyObject *text)
}
self->encoding_start_of_stream = 0;
}
else
else {
b = PyObject_CallMethodOneArg(self->encoder, _PyIO_str_encode, text);
}

Py_DECREF(text);
if (b == NULL)
Expand All @@ -1694,6 +1700,14 @@ _io_TextIOWrapper_write_impl(textio *self, PyObject *text)
self->pending_bytes_count = 0;
self->pending_bytes = b;
}
else if (self->pending_bytes_count + bytes_len > self->chunk_size) {
// Prevent to concatenate more than chunk_size data.
if (_textiowrapper_writeflush(self) < 0) {
Py_DECREF(b);
return NULL;
}
self->pending_bytes = b;
}
else if (!PyList_CheckExact(self->pending_bytes)) {
PyObject *list = PyList_New(2);
if (list == NULL) {
Expand All @@ -1713,7 +1727,7 @@ _io_TextIOWrapper_write_impl(textio *self, PyObject *text)
}

self->pending_bytes_count += bytes_len;
if (self->pending_bytes_count > self->chunk_size || needflush ||
if (self->pending_bytes_count >= self->chunk_size || needflush ||
text_needflush) {
if (_textiowrapper_writeflush(self) < 0)
return NULL;
Expand Down