From: Hirokazu Yamamoto <ocean-city@m2.ccsnet.ne.jp>
Date: Sat, 28 Feb 2009 10:31:54 +0000 (+0000)
Subject: Issue #5386: mmap.write_byte didn't check map size, so it could cause buffer
X-Git-Tag: v2.7a1~1927
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f2dc885780278246d1a4572c822c4387142a84df;p=python

Issue #5386: mmap.write_byte didn't check map size, so it could cause buffer
overrun.
---

diff --git a/Lib/test/test_mmap.py b/Lib/test/test_mmap.py
index c06b7579cc..c8e52a6b0c 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 04421f1a62..0ced9729e4 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -166,6 +166,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #5386: mmap.write_byte didn't check map size, so it could cause buffer
+  overrun.
+
 - Issue #1533164: Installed but not listed *.pyo was breaking Distutils
   bdist_rpm command.
 
diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index fad60d109f..8407c11b3b 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 *