[Python-checkins] cpython (2.7): avoid overflow with large buffer sizes and/or offsets (closes #21831)

[benjamin.peterson]

http://hg.python.org/cpython/rev/8d963c7db507
changeset:   91351:8d963c7db507
branch:      2.7
user:        Benjamin Peterson <benjamin at python.org>
date:        Mon Jun 23 20:12:27 2014 -0700
summary:
  avoid overflow with large buffer sizes and/or offsets (closes #21831)

files:
  Lib/test/test_buffer.py |  6 ++++++
  Misc/NEWS               |  3 +++
  Objects/bufferobject.c  |  4 ++--
  3 files changed, 11 insertions(+), 2 deletions(-)


diff --git a/Lib/test/test_buffer.py b/Lib/test/test_buffer.py
--- a/Lib/test/test_buffer.py
+++ b/Lib/test/test_buffer.py
@@ -4,6 +4,7 @@
 
 """
 
+import sys
 import unittest
 from test import test_support
 
@@ -29,6 +30,11 @@
         m = memoryview(b) # Should not raise an exception
         self.assertEqual(m.tobytes(), s)
 
+    def test_large_buffer_size_and_offset(self):
+        data = bytearray('hola mundo')
+        buf = buffer(data, sys.maxsize, sys.maxsize)
+        self.assertEqual(buf[:4096], "")
+
 
 def test_main():
     with test_support.check_py3k_warnings(("buffer.. not supported",
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Issue #21831: Avoid integer overflow when large sizes and offsets are given to
+  the buffer type.
+
 - Issue #1856: Avoid crashes and lockups when daemon threads run while the
   interpreter is shutting down; instead, these threads are now killed when they
   try to take the GIL.
diff --git a/Objects/bufferobject.c b/Objects/bufferobject.c
--- a/Objects/bufferobject.c
+++ b/Objects/bufferobject.c
@@ -88,7 +88,7 @@
             *size = count;
         else
             *size = self->b_size;
-        if (offset + *size > count)
+        if (*size > count - offset)
             *size = count - offset;
     }
     return 1;
@@ -875,4 +875,4 @@
     0,                                          /* tp_init */
     0,                                          /* tp_alloc */
     buffer_new,                                 /* tp_new */
-};
\ No newline at end of file
+};

-- 
Repository URL: http://hg.python.org/cpython