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gh-135836: Fix IndexError in asyncio.create_connection() #135875

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gh-135836: Fix IndexError in asyncio.create_connection() #135875

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2c7545f
gh-135836: Fix IndexError in asyncio.create_connection()
serhiy-storchaka Jun 24, 2025
2cb4cae
Make the test working on Windows.
serhiy-storchaka Jun 24, 2025
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62 changes: 32 additions & 30 deletions Lib/asyncio/base_events.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1016,38 +1016,40 @@ async def _connect_sock(self, exceptions, addr_info, local_addr_infos=None):
family, type_, proto, _, address = addr_info
sock = None
try:
sock = socket.socket(family=family, type=type_, proto=proto)
sock.setblocking(False)
if local_addr_infos is not None:
for lfamily, _, _, _, laddr in local_addr_infos:
# skip local addresses of different family
if lfamily != family:
continue
try:
sock.bind(laddr)
break
except OSError as exc:
msg = (
f'error while attempting to bind on '
f'address {laddr!r}: {str(exc).lower()}'
)
exc = OSError(exc.errno, msg)
my_exceptions.append(exc)
else: # all bind attempts failed
if my_exceptions:
raise my_exceptions.pop()
else:
raise OSError(f"no matching local address with {family=} found")
await self.sock_connect(sock, address)
return sock
except OSError as exc:
my_exceptions.append(exc)
if sock is not None:
sock.close()
raise
try:
sock = socket.socket(family=family, type=type_, proto=proto)
sock.setblocking(False)
if local_addr_infos is not None:
for lfamily, _, _, _, laddr in local_addr_infos:
# skip local addresses of different family
if lfamily != family:
continue
try:
sock.bind(laddr)
break
except OSError as exc:
msg = (
f'error while attempting to bind on '
f'address {laddr!r}: {str(exc).lower()}'
)
exc = OSError(exc.errno, msg)
my_exceptions.append(exc)
else: # all bind attempts failed
if my_exceptions:
raise my_exceptions.pop()
else:
raise OSError(f"no matching local address with {family=} found")
await self.sock_connect(sock, address)
return sock
except OSError as exc:
my_exceptions.append(exc)
raise
except:
if sock is not None:
sock.close()
try:
sock.close()
except OSError:
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I am not sure if suppressing this error is correct here.

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I think it is okay. It is an error in closing just created connection, it is less interesting than the original non-OSError error.

We do not even know what is this error, because we have no reproducer. ECONNRESET is already ignored in socket.close(). I suspect that this is similar error (maybe EINTR?) which should always be ignored.

pass
raise
finally:
exceptions = my_exceptions = None
Expand Down
29 changes: 29 additions & 0 deletions Lib/test/test_asyncio/test_base_events.py
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,10 @@
MOCK_ANY = mock.ANY


class CustomError(Exception):
pass


def tearDownModule():
asyncio._set_event_loop_policy(None)

Expand Down Expand Up @@ -1296,6 +1300,31 @@ def getaddrinfo_task(*args, **kwds):
self.assertEqual(len(cm.exception.exceptions), 1)
self.assertIsInstance(cm.exception.exceptions[0], OSError)

@patch_socket
def test_create_connection_connect_non_os_err_close_err(self, m_socket):
# Test the case when sock_connect() raises non-OSError exception
# and sock.close() raises OSError.
async def getaddrinfo(*args, **kw):
return [(2, 1, 6, '', ('107.6.106.82', 80))]

def getaddrinfo_task(*args, **kwds):
return self.loop.create_task(getaddrinfo(*args, **kwds))

self.loop.getaddrinfo = getaddrinfo_task
self.loop.sock_connect = mock.Mock()
self.loop.sock_connect.side_effect = CustomError
sock = mock.Mock()
m_socket.socket.return_value = sock
sock.close.side_effect = OSError

coro = self.loop.create_connection(MyProto, 'example.com', 80)
self.assertRaises(
CustomError, self.loop.run_until_complete, coro)

coro = self.loop.create_connection(MyProto, 'example.com', 80, all_errors=True)
self.assertRaises(
CustomError, self.loop.run_until_complete, coro)

def test_create_connection_multiple(self):
async def getaddrinfo(*args, **kw):
return [(2, 1, 6, '', ('0.0.0.1', 80)),
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2025-06-24-10-52-35.gh-issue-135836.s37351.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix :exc:`IndexError` in :meth:`asyncio.loop.create_connection` that could
occur when non-\ :exc:`OSError` exception is raised during connection and
socket's ``close()`` raises :exc:`!OSError`.
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