# HG changeset patch

# User Benjamin Peterson <benjamin@python.org>

# Date 1389671978 18000

# Node ID 87673659d8f7ba1623cd4914f09ad3d2ade034e9

# Parent  2631d33ee7fbd5f0288931ef37872218d511d2e8

complain when nbytes > buflen to fix possible buffer overflow (closes #20246)

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");

+        goto error;

     }

     readlen = sock_recvfrom_guts(s, buf.buf, recvlen, flags, &addr);