Close #13022: _multiprocessing.recvfd() doesn't check that file descriptor was actually received
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index c2a2f19..0e480a9 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -1574,6 +1574,23 @@
with open(test_support.TESTFN, "rb") as f:
self.assertEqual(f.read(), b"bar")
+ @classmethod
+ def _send_data_without_fd(self, conn):
+ os.write(conn.fileno(), b"\0")
+
+ @unittest.skipIf(sys.platform == "win32", "doesn't make sense on Windows")
+ def test_missing_fd_transfer(self):
+ # Check that exception is raised when received data is not
+ # accompanied by a file descriptor in ancillary data.
+ if self.TYPE != 'processes':
+ self.skipTest("only makes sense with processes")
+ conn, child_conn = self.Pipe(duplex=True)
+
+ p = self.Process(target=self._send_data_without_fd, args=(child_conn,))
+ p.daemon = True
+ p.start()
+ self.assertRaises(RuntimeError, reduction.recv_handle, conn)
+ p.join()
class _TestListenerClient(BaseTestCase):
diff --git a/Misc/NEWS b/Misc/NEWS
index 30cde1d..fa4022e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -201,6 +201,9 @@
Extension Modules
-----------------
+- Issue #13022: Fix: _multiprocessing.recvfd() doesn't check that
+ file descriptor was actually received.
+
- Issue #12483: ctypes: Fix a crash when the destruction of a callback
object triggers the garbage collector.
diff --git a/Modules/_multiprocessing/multiprocessing.c b/Modules/_multiprocessing/multiprocessing.c
index 7582664..31a8da8 100644
--- a/Modules/_multiprocessing/multiprocessing.c
+++ b/Modules/_multiprocessing/multiprocessing.c
@@ -177,6 +177,17 @@
if (res < 0)
return PyErr_SetFromErrno(PyExc_OSError);
+ if (msg.msg_controllen < CMSG_LEN(sizeof(int)) ||
+ (cmsg = CMSG_FIRSTHDR(&msg)) == NULL ||
+ cmsg->cmsg_level != SOL_SOCKET ||
+ cmsg->cmsg_type != SCM_RIGHTS ||
+ cmsg->cmsg_len < CMSG_LEN(sizeof(int))) {
+ /* If at least one control message is present, there should be
+ no room for any further data in the buffer. */
+ PyErr_SetString(PyExc_RuntimeError, "No file descriptor received");
+ return NULL;
+ }
+
fd = * (int *) CMSG_DATA(cmsg);
return Py_BuildValue("i", fd);
}