# HG changeset patch
# User Benjamin Peterson <benjamin@python.org>
# Date 1389671978 18000
# Node ID 9c56217e5c793685eeaf0ee224848c402bdf1e4c
# Parent  2b5cd6d4d149dea6c6941b7e07ada248b29fc9f6
complain when nbytes > buflen to fix possible buffer overflow (closes #20246)

# HG changeset patch
# User Stefan Krah <skrah@bytereef.org>
# Date 1390341520 -3600
# Node ID e82dcd700e8cfb174d6bf6031fd6666627b20f5f
# Parent  29b1eebecb8ed946e1db8e4bb86310d681cf4a91
Issue #20246: Fix test failures on FreeBSD. Patch by Ryan Smith-Roberts.

diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
--- Lib/test/test_socket.py
+++ Lib/test/test_socket.py
@@ -1968,6 +1968,14 @@ 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):
+        self.serv_conn.send(MSG)
+
 
 TIPC_STYPE = 2000
 TIPC_LOWER = 200

diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
--- Modules/socketmodule.c
+++ Modules/socketmodule.c
@@ -2598,6 +2598,11 @@ sock_recvfrom_into(PySocketSockObject *s
     if (recvlen == 0) {
         /* If nbytes was not specified, use the buffer's length */
         recvlen = buflen;
+    } else if (recvlen > buflen) {
+        PyBuffer_Release(&pbuf);
+        PyErr_SetString(PyExc_ValueError,
+                        "nbytes is greater than the length of the buffer");
+        return NULL;
     }
 
     readlen = sock_recvfrom_guts(s, buf, recvlen, flags, &addr);