Backport fixes to set objects:

rev 52964 sf 1576657 KeyError unpacks tuple arguments
rev 52963 sf 1456209 obscure resizing vulnerability
rev 52962 redundant calls to PyObject_Hash()

Lib/test/test_set.py

@@ -293,6 +293,17 @@ class TestSet(TestJointOps):
         self.assert_(self.thetype(self.word) not in s)
         self.assertRaises(KeyError, self.s.remove, self.thetype(self.word))
 
+    def test_remove_keyerror_unpacking(self):
+        # bug:  www.python.org/sf/1576657
+        for v1 in ['Q', (1,)]:
+            try:
+                self.s.remove(v1)
+            except KeyError, e:
+                v2 = e.args[0]
+                self.assertEqual(v1, v2)
+            else:
+                self.fail()
+
     def test_discard(self):
         self.s.discard('a')
         self.assert_('a' not in self.s)

Misc/NEWS

@@ -12,12 +12,20 @@ What's New in Python 2.5.1c1?
 Core and builtins
 -----------------
 
+- Bug #1456209: In some obscure cases it was possible for a class with a
+  custom ``__eq__()`` method to confuse set internals when class instances
+  were used as a set's elements and the ``__eq__()`` method mutated the set.
+
+- Eliminated unnecessary repeated calls to hash() by set.intersection() and
+  set.symmetric_difference_update().
+
 - Bug #1591996: Correctly forward exception in instance_contains().
 
 - Bug #1588287: fix invalid assertion for `1,2` in debug builds.
 
 - Bug #1576657: when setting a KeyError for a tuple key, make sure that
-  the tuple isn't used as the "exception arguments tuple".
+  the tuple isn't used as the "exception arguments tuple".  Applied to
+  both sets and dictionaries.
 
 - Bug #1565514, SystemError not raised on too many nested blocks.
 

Objects/setobject.c

@@ -10,6 +10,20 @@
 #include "Python.h"
 #include "structmember.h"
 
+/* Set a key error with the specified argument, wrapping it in a
+ * tuple automatically so that tuple keys are not unpacked as the
+ * exception arguments. */
+static void
+set_key_error(PyObject *arg)
+{
+	PyObject *tup;
+	tup = PyTuple_Pack(1, arg);
+	if (!tup)
+		return; /* caller will expect error to be set anyway */
+	PyErr_SetObject(PyExc_KeyError, tup);
+	Py_DECREF(tup);
+}
+
 /* This must be >= 1. */
 #define PERTURB_SHIFT 5
 
@@ -185,7 +199,7 @@ set_lookkey_string(PySetObject *so, PyObject *key, register long hash)
 
 /*
 Internal routine to insert a new key into the table.
-Used both by the internal resize routine and by the public insert routine.
+Used by the public insert routine.
 Eats a reference to key.
 */
 static int
@@ -217,6 +231,35 @@ set_insert_key(register PySetObject *so, PyObject *key, long hash)
 	return 0;
 }
 
+/*
+Internal routine used by set_table_resize() to insert an item which is
+known to be absent from the set.  This routine also assumes that
+the set contains no deleted entries.  Besides the performance benefit,
+using set_insert_clean() in set_table_resize() is dangerous (SF bug #1456209).
+Note that no refcounts are changed by this routine; if needed, the caller
+is responsible for incref'ing `key`.
+*/
+static void
+set_insert_clean(register PySetObject *so, PyObject *key, long hash)
+{
+	register size_t i;
+	register size_t perturb;
+	register size_t mask = (size_t)so->mask;
+	setentry *table = so->table;
+	register setentry *entry;
+
+	i = hash & mask;
+	entry = &table[i];
+	for (perturb = hash; entry->key != NULL; perturb >>= PERTURB_SHIFT) {
+		i = (i << 2) + i + perturb + 1;
+		entry = &table[i & mask];
+	}
+	so->fill++;
+	entry->key = key;
+	entry->hash = hash;
+	so->used++;
+}
+
 /*
 Restructure the table by allocating a new table and reinserting all
 keys again.  When entries have been deleted, the new table may
@@ -298,11 +341,7 @@ set_table_resize(PySetObject *so, Py_ssize_t minused)
 		} else {
 			/* ACTIVE */
 			--i;
-			if(set_insert_key(so, entry->key, entry->hash) == -1) {
-				if (is_oldtable_malloced)
-					PyMem_DEL(oldtable);
-				return -1;
-			}
+			set_insert_clean(so, entry->key, entry->hash);
 		}
 	}
 
@@ -1164,7 +1203,19 @@ set_intersection(PySetObject *so, PyObject *other)
 	}
 
 	while ((key = PyIter_Next(it)) != NULL) {
-		int rv = set_contains_key(so, key);
+		int rv;
+		setentry entry;
+		long hash = PyObject_Hash(key);
+
+		if (hash == -1) {
+			Py_DECREF(it);
+			Py_DECREF(result);
+			Py_DECREF(key);
+			return NULL;
+		}
+		entry.hash = hash;
+		entry.key = key;
+		rv = set_contains_entry(so, &entry);
 		if (rv == -1) {
 			Py_DECREF(it);
 			Py_DECREF(result);
@@ -1172,7 +1223,7 @@ set_intersection(PySetObject *so, PyObject *other)
 			return NULL;
 		}
 		if (rv) {
-			if (set_add_key(result, key) == -1) {
+			if (set_add_entry(result, &entry) == -1) {
 				Py_DECREF(it);
 				Py_DECREF(result);
 				Py_DECREF(key);
@@ -1383,11 +1434,18 @@ set_symmetric_difference_update(PySetObject *so, PyObject *other)
 		PyObject *value;
 		int rv;
 		while (PyDict_Next(other, &pos, &key, &value)) {
-			rv = set_discard_key(so, key);
+			setentry an_entry;
+			long hash = PyObject_Hash(key);
+
+			if (hash == -1)
+				return NULL;
+			an_entry.hash = hash;
+			an_entry.key = key;
+			rv = set_discard_entry(so, &an_entry);
 			if (rv == -1)
 				return NULL;
 			if (rv == DISCARD_NOTFOUND) {
-				if (set_add_key(so, key) == -1)
+				if (set_add_entry(so, &an_entry) == -1)
 					return NULL;
 			}
 		}
@@ -1640,7 +1698,7 @@ set_remove(PySetObject *so, PyObject *key)
 		Py_DECREF(tmpkey);
 		return result;
 	} else if (rv == DISCARD_NOTFOUND) {
-		PyErr_SetObject(PyExc_KeyError, key);
+		set_key_error(key);
 		return NULL;
 	}
 	Py_RETURN_NONE;