Merged revisions 88131 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/branches/py3k

........
  r88131 | antoine.pitrou | 2011-01-20 22:07:24 +0100 (jeu., 20 janv. 2011) | 6 lines

  Issue #10955: Fix a potential crash when trying to mmap() a file past its
  length.  Initial patch by Ross Lagerwall.

  This fixes a regression introduced by r88022.
........
diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index 0e91f2c..4b2a971 100644
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -1164,6 +1164,11 @@
 #  endif
     if (fd != -1 && fstat(fd, &st) == 0 && S_ISREG(st.st_mode)) {
         if (map_size == 0) {
+            if (offset >= st.st_size) {
+                PyErr_SetString(PyExc_ValueError,
+                                "mmap offset is greater than file size");
+                return NULL;
+            }
             map_size = st.st_size - offset;
         } else if ((size_t)offset + (size_t)map_size > st.st_size) {
             PyErr_SetString(PyExc_ValueError,
@@ -1346,6 +1351,12 @@
             else
                 m_obj->size = low;
 #endif
+            if (offset >= m_obj->size) {
+                PyErr_SetString(PyExc_ValueError,
+                                "mmap offset is greater than file size");
+                Py_DECREF(m_obj);
+                return NULL;
+            }
             m_obj->size -= offset;
         } else {
             m_obj->size = map_size;