Bug 1688393. Adds a control of negative values in

socket.recvfrom, which caused an ugly crash.

Lib/test/test_socket.py

@@ -597,6 +597,13 @@ class BasicUDPTest(ThreadedUDPSocketTest):
     def _testRecvFrom(self):
         self.cli.sendto(MSG, 0, (HOST, PORT))
 
+    def testRecvFromNegative(self):
+        # Negative lengths passed to recvfrom should give ValueError.
+        self.assertRaises(ValueError, self.serv.recvfrom, -1)
+
+    def _testRecvFromNegative(self):
+        self.cli.sendto(MSG, 0, (HOST, PORT))
+
 class TCPCloserTest(ThreadedTCPSocketTest):
 
     def testClose(self):

Modules/socketmodule.c

@@ -2391,7 +2391,7 @@ sock_recv_into(PySocketSockObject *s, PyObject *args, PyObject *kwds)
 
 	if (recvlen < 0) {
 		PyErr_SetString(PyExc_ValueError,
-				"negative buffersize in recv");
+				"negative buffersize in recv_into");
 		return NULL;
 	}
 	if (recvlen == 0) {
@@ -2507,6 +2507,12 @@ sock_recvfrom(PySocketSockObject *s, PyObject *args)
 	if (!PyArg_ParseTuple(args, "i|i:recvfrom", &recvlen, &flags))
 		return NULL;
 
+	if (recvlen < 0) {
+		PyErr_SetString(PyExc_ValueError,
+				"negative buffersize in recvfrom");
+		return NULL;
+	}
+
 	buf = PyString_FromStringAndSize((char *) 0, recvlen);
 	if (buf == NULL)
 		return NULL;
@@ -2560,7 +2566,7 @@ sock_recvfrom_into(PySocketSockObject *s, PyObject *args, PyObject* kwds)
 
 	if (recvlen < 0) {
 		PyErr_SetString(PyExc_ValueError,
-				"negative buffersize in recv");
+				"negative buffersize in recvfrom_into");
 		return NULL;
 	}
 	if (recvlen == 0) {