diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -1620,6 +1620,16 @@ class BufferIOTest(SocketConnectedTest):
_testRecvFromIntoMemoryview = _testRecvFromIntoArray
+ def testRecvFromIntoSmallBuffer(self):
+ # See issue #20246.
+ buf = bytearray(8)
+ self.assertRaises(ValueError, self.cli_conn.recvfrom_into, buf, 1024)
+
+ def _testRecvFromIntoSmallBuffer(self):
+ with test_support.check_py3k_warnings():
+ buf = buffer(MSG*2048)
+ self.serv_conn.send(buf)
+
TIPC_STYPE = 2000
TIPC_LOWER = 200
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -2742,6 +2742,10 @@ sock_recvfrom_into(PySocketSockObject *s
if (recvlen == 0) {
/* If nbytes was not specified, use the buffer's length */
recvlen = buflen;
+ } else if (recvlen > buflen) {
+ PyErr_SetString(PyExc_ValueError,
+ "nbytes is greater than the length of the buffer");
+ return NULL;
}
readlen = sock_recvfrom_guts(s, buf.buf, recvlen, flags, &addr);