diff --git a/Objects/bufferobject.c b/Objects/bufferobject.c
index 3bd8c6b..9a5c39f 100644
--- a/Objects/bufferobject.c
+++ b/Objects/bufferobject.c
@@ -431,6 +431,10 @@
 		count = 0;
 	if (!get_buf(self, &ptr, &size, ANY_BUFFER))
 		return NULL;
+	if (count > PY_SSIZE_T_MAX / size) {
+		PyErr_SetString(PyExc_MemoryError, "result too large");
+		return NULL;
+	}
 	ob = PyString_FromStringAndSize(NULL, size * count);
 	if ( ob == NULL )
 		return NULL;
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 2c228bb..228376a 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -70,6 +70,8 @@
 		return NULL;
 	}
 	/* coverity[ampersand_in_size] */
+	/* XXX(nnorwitz): This can overflow --
+           PyObject_NEW_VAR / _PyObject_VAR_SIZE need to detect overflow */
 	return PyObject_NEW_VAR(PyLongObject, &PyLong_Type, size);
 }
 
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index 793cc88..0d2ceb1 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -74,6 +74,11 @@
 		return (PyObject *)op;
 	}
 
+	if (size > PY_SSIZE_T_MAX - sizeof(PyStringObject)) {
+		PyErr_SetString(PyExc_OverflowError, "string is too large");
+		return NULL;
+	}
+
 	/* Inline PyObject_NewVar */
 	op = (PyStringObject *)PyObject_MALLOC(sizeof(PyStringObject) + size);
 	if (op == NULL)
@@ -109,7 +114,7 @@
 
 	assert(str != NULL);
 	size = strlen(str);
-	if (size > PY_SSIZE_T_MAX) {
+	if (size > PY_SSIZE_T_MAX - sizeof(PyStringObject)) {
 		PyErr_SetString(PyExc_OverflowError,
 			"string is too long for a Python string");
 		return NULL;
@@ -977,13 +982,23 @@
 		return (PyObject *)a;
 	}
 	size = Py_SIZE(a) + Py_SIZE(b);
-	if (size < 0) {
+	/* Check that string sizes are not negative, to prevent an
+	   overflow in cases where we are passed incorrectly-created
+	   strings with negative lengths (due to a bug in other code).
+        */
+	if (Py_SIZE(a) < 0 || Py_SIZE(b) < 0 ||
+	    Py_SIZE(a) > PY_SSIZE_T_MAX - Py_SIZE(b)) {
 		PyErr_SetString(PyExc_OverflowError,
 				"strings are too large to concat");
 		return NULL;
 	}
 	  
 	/* Inline PyObject_NewVar */
+	if (size > PY_SSIZE_T_MAX - sizeof(PyStringObject)) {
+		PyErr_SetString(PyExc_OverflowError,
+				"strings are too large to concat");
+		return NULL;
+	}
 	op = (PyStringObject *)PyObject_MALLOC(sizeof(PyStringObject) + size);
 	if (op == NULL)
 		return PyErr_NoMemory();
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 79d7553..348ae8c 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -60,11 +60,12 @@
 		Py_ssize_t nbytes = size * sizeof(PyObject *);
 		/* Check for overflow */
 		if (nbytes / sizeof(PyObject *) != (size_t)size ||
-		    (nbytes += sizeof(PyTupleObject) - sizeof(PyObject *))
-		    <= 0)
+		    (nbytes > PY_SSIZE_T_MAX - sizeof(PyTupleObject) - sizeof(PyObject *)))
 		{
 			return PyErr_NoMemory();
 		}
+		nbytes += sizeof(PyTupleObject) - sizeof(PyObject *);
+
 		op = PyObject_GC_NewVar(PyTupleObject, &PyTuple_Type, size);
 		if (op == NULL)
 			return NULL;
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 16d97c3..7abf984 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -299,6 +299,11 @@
         return unicode_empty;
     }
 
+    /* Ensure we won't overflow the size. */
+    if (length > ((PY_SSIZE_T_MAX / sizeof(Py_UNICODE)) - 1)) {
+        return (PyUnicodeObject *)PyErr_NoMemory();
+    }
+
     /* Unicode freelist & memory allocation */
     if (free_list) {
         unicode = free_list;
@@ -1651,6 +1656,9 @@
     char * out;
     char * start;
 
+    if (cbAllocated / 5 != size)
+        return PyErr_NoMemory();
+
     if (size == 0)
 		return PyString_FromStringAndSize(NULL, 0);
 
@@ -2245,8 +2253,9 @@
 {
     PyObject *v;
     unsigned char *p;
+    Py_ssize_t nsize, bytesize;
 #ifndef Py_UNICODE_WIDE
-    int i, pairs;
+    Py_ssize_t i, pairs;
 #else
     const int pairs = 0;
 #endif
@@ -2274,8 +2283,11 @@
 	    0xDC00 <= s[i+1] && s[i+1] <= 0xDFFF)
 	    pairs++;
 #endif
-    v = PyString_FromStringAndSize(NULL,
-		  4 * (size - pairs + (byteorder == 0)));
+    nsize = (size - pairs + (byteorder == 0));
+    bytesize = nsize * 4;
+    if (bytesize / 4 != nsize)
+	return PyErr_NoMemory();
+    v = PyString_FromStringAndSize(NULL, bytesize);
     if (v == NULL)
         return NULL;
 
@@ -2515,8 +2527,9 @@
 {
     PyObject *v;
     unsigned char *p;
+    Py_ssize_t nsize, bytesize;
 #ifdef Py_UNICODE_WIDE
-    int i, pairs;
+    Py_ssize_t i, pairs;
 #else
     const int pairs = 0;
 #endif
@@ -2539,8 +2552,15 @@
 	if (s[i] >= 0x10000)
 	    pairs++;
 #endif
-    v = PyString_FromStringAndSize(NULL,
-		  2 * (size + pairs + (byteorder == 0)));
+    /* 2 * (size + pairs + (byteorder == 0)) */
+    if (size > PY_SSIZE_T_MAX ||
+        size > PY_SSIZE_T_MAX - pairs - (byteorder == 0))
+	return PyErr_NoMemory();
+    nsize = size + pairs + (byteorder == 0);
+    bytesize = nsize * 2;
+    if (bytesize / 2 != nsize)
+	return PyErr_NoMemory();
+    v = PyString_FromStringAndSize(NULL, bytesize);
     if (v == NULL)
         return NULL;
 
@@ -2868,6 +2888,11 @@
     char *p;
 
     static const char *hexdigit = "0123456789abcdef";
+#ifdef Py_UNICODE_WIDE
+    const Py_ssize_t expandsize = 10;
+#else
+    const Py_ssize_t expandsize = 6;
+#endif
 
     /* XXX(nnorwitz): rather than over-allocating, it would be
        better to choose a different scheme.  Perhaps scan the
@@ -2887,13 +2912,12 @@
        escape.
     */
 
+    if (size > (PY_SSIZE_T_MAX - 2 - 1) / expandsize)
+	return PyErr_NoMemory();
+
     repr = PyString_FromStringAndSize(NULL,
         2
-#ifdef Py_UNICODE_WIDE
-        + 10*size
-#else
-        + 6*size
-#endif
+        + expandsize*size
         + 1);
     if (repr == NULL)
         return NULL;
@@ -3146,12 +3170,16 @@
     char *q;
 
     static const char *hexdigit = "0123456789abcdef";
-
 #ifdef Py_UNICODE_WIDE
-    repr = PyString_FromStringAndSize(NULL, 10 * size);
+    const Py_ssize_t expandsize = 10;
 #else
-    repr = PyString_FromStringAndSize(NULL, 6 * size);
+    const Py_ssize_t expandsize = 6;
 #endif
+    
+    if (size > PY_SSIZE_T_MAX / expandsize)
+	return PyErr_NoMemory();
+    
+    repr = PyString_FromStringAndSize(NULL, expandsize * size);
     if (repr == NULL)
         return NULL;
     if (size == 0)
@@ -5574,6 +5602,11 @@
         return self;
     }
 
+    if (left > PY_SSIZE_T_MAX - self->length ||
+        right > PY_SSIZE_T_MAX - (left + self->length)) {
+        PyErr_SetString(PyExc_OverflowError, "padded string is too long");
+        return NULL;
+    }
     u = _PyUnicode_New(left + self->length + right);
     if (u) {
         if (left)