From e363fa020b1775879f16bac99e2eb5f1d42f8fd3 Mon Sep 17 00:00:00 2001
From: Hirokazu Yamamoto <ocean-city@m2.ccsnet.ne.jp>
Date: Sat, 28 Feb 2009 11:39:45 +0000
Subject: [PATCH] Merged revisions 70052 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/trunk

........
  r70052 | hirokazu.yamamoto | 2009-02-28 19:31:54 +0900 | 2 lines

  Issue #5386: mmap.write_byte didn't check map size, so it could cause buffer
  overrun.
........
---
 Lib/test/test_mmap.py | 32 ++++++++++++++++++++++++++++++++
 Misc/NEWS             |  3 +++
 Modules/mmapmodule.c  | 15 +++++++++++----
 3 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/Lib/test/test_mmap.py b/Lib/test/test_mmap.py
index c06b7579ccd7..c8e52a6b0c1c 100644
--- a/Lib/test/test_mmap.py
+++ b/Lib/test/test_mmap.py
@@ -467,6 +467,38 @@ class MmapTests(unittest.TestCase):
         self.assert_(issubclass(mmap.error, EnvironmentError))
         self.assert_("mmap.error" in str(mmap.error))
 
+    def test_io_methods(self):
+        data = "0123456789"
+        open(TESTFN, "wb").write("x"*len(data))
+        f = open(TESTFN, "r+b")
+        m = mmap.mmap(f.fileno(), len(data))
+        f.close()
+        # Test write_byte()
+        for i in xrange(len(data)):
+            self.assertEquals(m.tell(), i)
+            m.write_byte(data[i:i+1])
+            self.assertEquals(m.tell(), i+1)
+        self.assertRaises(ValueError, m.write_byte, "x")
+        self.assertEquals(m[:], data)
+        # Test read_byte()
+        m.seek(0)
+        for i in xrange(len(data)):
+            self.assertEquals(m.tell(), i)
+            self.assertEquals(m.read_byte(), data[i:i+1])
+            self.assertEquals(m.tell(), i+1)
+        self.assertRaises(ValueError, m.read_byte)
+        # Test read()
+        m.seek(3)
+        self.assertEquals(m.read(3), "345")
+        self.assertEquals(m.tell(), 6)
+        # Test write()
+        m.seek(3)
+        m.write("bar")
+        self.assertEquals(m.tell(), 6)
+        self.assertEquals(m[:], "012bar6789")
+        m.seek(8)
+        self.assertRaises(ValueError, m.write, "bar")
+
 
 def test_main():
     run_unittest(MmapTests)
diff --git a/Misc/NEWS b/Misc/NEWS
index efa19a20a578..3553dbc47a4a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -89,6 +89,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #5386: mmap.write_byte didn't check map size, so it could cause buffer
+  overrun.
+
 - Issue #5292: Fixed mmap crash on its boundary access m[len(m)].
 
 - Issue #5282: Fixed mmap resize on 32bit windows and unix. When offset > 0,
diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index fad60d109f8c..8407c11b3be2 100644
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -365,10 +365,17 @@ mmap_write_byte_method(mmap_object *self,
 
 	if (!is_writeable(self))
 		return NULL;
-	*(self->data+self->pos) = value;
-	self->pos += 1;
-	Py_INCREF(Py_None);
-	return Py_None;
+
+	if (self->pos < self->size) {
+		*(self->data+self->pos) = value;
+		self->pos += 1;
+		Py_INCREF(Py_None);
+		return Py_None;
+	}
+	else {
+		PyErr_SetString(PyExc_ValueError, "write byte out of range");
+		return NULL;
+	}
 }
 
 static PyObject *
-- 
2.47.3