[Python-checkins] cpython: Fix crash in itertools.cycle.__setstate__() caused by lack of type checking.

[raymond.hettinger]

https://hg.python.org/cpython/rev/a4d5ef7fdec3
changeset:   97390:a4d5ef7fdec3
user:        Raymond Hettinger <python at rcn.com>
date:        Sat Aug 15 13:51:59 2015 -0700
summary:
  Fix crash in itertools.cycle.__setstate__() caused by lack of type checking.

Will backport after the 3.6 release is done.

files:
  Lib/test/test_itertools.py |  33 ++++++++++++++++++++++++++
  Misc/NEWS                  |   3 ++
  Modules/itertoolsmodule.c  |   2 +-
  3 files changed, 37 insertions(+), 1 deletions(-)


diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -613,6 +613,39 @@
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             self.pickletest(proto, cycle('abc'))
 
+    def test_cycle_setstate(self):
+        # Verify both modes for restoring state
+
+        # Mode 0 is efficient.  It uses an incompletely consumed input
+        # iterator to build a cycle object and then passes in state with
+        # a list of previously consumed values.  There is no data
+        # overlap bewteen the two.
+        c = cycle('defg')
+        c.__setstate__((list('abc'), 0))
+        self.assertEqual(take(20, c), list('defgabcdefgabcdefgab'))
+
+        # Mode 1 is inefficient.  It starts with a cycle object built
+        # from an iterator over the remaining elements in a partial
+        # cycle and then passes in state with all of the previously
+        # seen values (this overlaps values included in the iterator).
+        c = cycle('defg')
+        c.__setstate__((list('abcdefg'), 1))
+        self.assertEqual(take(20, c), list('defgabcdefgabcdefgab'))
+
+        # The first argument to setstate needs to be a tuple
+        with self.assertRaises(SystemError):
+            cycle('defg').__setstate__([list('abcdefg'), 0])
+
+        # The first argument in the setstate tuple must be a list
+        with self.assertRaises(TypeError):
+            c = cycle('defg')
+            c.__setstate__((dict.fromkeys('defg'), 0))
+            take(20, c)
+
+        # The first argument in the setstate tuple must be a list
+        with self.assertRaises(TypeError):
+            cycle('defg').__setstate__((list('abcdefg'), 'x'))
+
     def test_groupby(self):
         # Check whether it accepts arguments correctly
         self.assertEqual([], list(groupby([])))
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -25,6 +25,9 @@
 - Issue #21159: Improve message in configparser.InterpolationMissingOptionError.
   Patch from Łukasz Langa.
 
+- Fix crash in itertools.cycle.__setstate__() when the first argument wasn't
+  a list.
+
 - Issue #20059: urllib.parse raises ValueError on all invalid ports.
   Patch by Martin Panter.
 
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -973,7 +973,7 @@
 {
     PyObject *saved=NULL;
     int firstpass;
-    if (!PyArg_ParseTuple(state, "Oi", &saved, &firstpass))
+    if (!PyArg_ParseTuple(state, "O!i", &PyList_Type, &saved, &firstpass))
         return NULL;
     Py_CLEAR(lz->saved);
     lz->saved = saved;

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