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closes bpo-34656: Avoid relying on signed overflow in _pickle memos. (G…

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benjaminp committed Sep 21, 2018
1 parent f14c28f commit a4ae828ee416a66d8c7bf5ee71d653c2cc6a26dd
Showing with 31 additions and 31 deletions.
  1. +31 −31 Modules/_pickle.c
@@ -602,9 +602,9 @@ typedef struct {
} PyMemoEntry;

typedef struct {
Py_ssize_t mt_mask;
Py_ssize_t mt_used;
Py_ssize_t mt_allocated;
size_t mt_mask;
size_t mt_used;
size_t mt_allocated;
PyMemoEntry *mt_table;
} PyMemoTable;

@@ -650,8 +650,8 @@ typedef struct UnpicklerObject {
/* The unpickler memo is just an array of PyObject *s. Using a dict
is unnecessary, since the keys are contiguous ints. */
PyObject **memo;
Py_ssize_t memo_size; /* Capacity of the memo array */
Py_ssize_t memo_len; /* Number of objects in the memo */
size_t memo_size; /* Capacity of the memo array */
size_t memo_len; /* Number of objects in the memo */

PyObject *pers_func; /* persistent_load() method, can be NULL. */
PyObject *pers_func_self; /* borrowed reference to self if pers_func
@@ -737,7 +737,6 @@ PyMemoTable_New(void)
static PyMemoTable *
PyMemoTable_Copy(PyMemoTable *self)
{
Py_ssize_t i;
PyMemoTable *new = PyMemoTable_New();
if (new == NULL)
return NULL;
@@ -754,7 +753,7 @@ PyMemoTable_Copy(PyMemoTable *self)
PyErr_NoMemory();
return NULL;
}
for (i = 0; i < self->mt_allocated; i++) {
for (size_t i = 0; i < self->mt_allocated; i++) {
Py_XINCREF(self->mt_table[i].me_key);
}
memcpy(new->mt_table, self->mt_table,
@@ -800,7 +799,7 @@ _PyMemoTable_Lookup(PyMemoTable *self, PyObject *key)
{
size_t i;
size_t perturb;
size_t mask = (size_t)self->mt_mask;
size_t mask = self->mt_mask;
PyMemoEntry *table = self->mt_table;
PyMemoEntry *entry;
Py_hash_t hash = (Py_hash_t)key >> 3;
@@ -821,22 +820,24 @@ _PyMemoTable_Lookup(PyMemoTable *self, PyObject *key)

/* Returns -1 on failure, 0 on success. */
static int
_PyMemoTable_ResizeTable(PyMemoTable *self, Py_ssize_t min_size)
_PyMemoTable_ResizeTable(PyMemoTable *self, size_t min_size)
{
PyMemoEntry *oldtable = NULL;
PyMemoEntry *oldentry, *newentry;
Py_ssize_t new_size = MT_MINSIZE;
Py_ssize_t to_process;
size_t new_size = MT_MINSIZE;
size_t to_process;

assert(min_size > 0);

/* Find the smallest valid table size >= min_size. */
while (new_size < min_size && new_size > 0)
new_size <<= 1;
if (new_size <= 0) {
if (min_size > PY_SSIZE_T_MAX) {
PyErr_NoMemory();
return -1;
}

/* Find the smallest valid table size >= min_size. */
while (new_size < min_size) {
new_size <<= 1;
}
/* new_size needs to be a power of two. */
assert((new_size & (new_size - 1)) == 0);

@@ -909,10 +910,12 @@ PyMemoTable_Set(PyMemoTable *self, PyObject *key, Py_ssize_t value)
* Very large memo tables (over 50K items) use doubling instead.
* This may help applications with severe memory constraints.
*/
if (!(self->mt_used * 3 >= (self->mt_mask + 1) * 2))
if (SIZE_MAX / 3 >= self->mt_used && self->mt_used * 3 < self->mt_allocated * 2) {
return 0;
return _PyMemoTable_ResizeTable(self,
(self->mt_used > 50000 ? 2 : 4) * self->mt_used);
}
// self->mt_used is always < PY_SSIZE_T_MAX, so this can't overflow.
size_t desired_size = (self->mt_used > 50000 ? 2 : 4) * self->mt_used;
return _PyMemoTable_ResizeTable(self, desired_size);
}

#undef MT_MINSIZE
@@ -1376,9 +1379,9 @@ _Unpickler_Readline(UnpicklerObject *self, char **result)
/* Returns -1 (with an exception set) on failure, 0 on success. The memo array
will be modified in place. */
static int
_Unpickler_ResizeMemoList(UnpicklerObject *self, Py_ssize_t new_size)
_Unpickler_ResizeMemoList(UnpicklerObject *self, size_t new_size)
{
Py_ssize_t i;
size_t i;

assert(new_size > self->memo_size);

@@ -1397,9 +1400,9 @@ _Unpickler_ResizeMemoList(UnpicklerObject *self, Py_ssize_t new_size)

/* Returns NULL if idx is out of bounds. */
static PyObject *
_Unpickler_MemoGet(UnpicklerObject *self, Py_ssize_t idx)
_Unpickler_MemoGet(UnpicklerObject *self, size_t idx)
{
if (idx < 0 || idx >= self->memo_size)
if (idx >= self->memo_size)
return NULL;

return self->memo[idx];
@@ -1408,7 +1411,7 @@ _Unpickler_MemoGet(UnpicklerObject *self, Py_ssize_t idx)
/* Returns -1 (with an exception set) on failure, 0 on success.
This takes its own reference to `value`. */
static int
_Unpickler_MemoPut(UnpicklerObject *self, Py_ssize_t idx, PyObject *value)
_Unpickler_MemoPut(UnpicklerObject *self, size_t idx, PyObject *value)
{
PyObject *old_item;

@@ -4413,14 +4416,13 @@ static PyObject *
_pickle_PicklerMemoProxy_copy_impl(PicklerMemoProxyObject *self)
/*[clinic end generated code: output=bb83a919d29225ef input=b73043485ac30b36]*/
{
Py_ssize_t i;
PyMemoTable *memo;
PyObject *new_memo = PyDict_New();
if (new_memo == NULL)
return NULL;

memo = self->pickler->memo;
for (i = 0; i < memo->mt_allocated; ++i) {
for (size_t i = 0; i < memo->mt_allocated; ++i) {
PyMemoEntry entry = memo->mt_table[i];
if (entry.me_key != NULL) {
int status;
@@ -6843,7 +6845,7 @@ static PyObject *
_pickle_UnpicklerMemoProxy_copy_impl(UnpicklerMemoProxyObject *self)
/*[clinic end generated code: output=e12af7e9bc1e4c77 input=97769247ce032c1d]*/
{
Py_ssize_t i;
size_t i;
PyObject *new_memo = PyDict_New();
if (new_memo == NULL)
return NULL;
@@ -6994,8 +6996,7 @@ static int
Unpickler_set_memo(UnpicklerObject *self, PyObject *obj)
{
PyObject **new_memo;
Py_ssize_t new_memo_size = 0;
Py_ssize_t i;
size_t new_memo_size = 0;

if (obj == NULL) {
PyErr_SetString(PyExc_TypeError,
@@ -7012,7 +7013,7 @@ Unpickler_set_memo(UnpicklerObject *self, PyObject *obj)
if (new_memo == NULL)
return -1;

for (i = 0; i < new_memo_size; i++) {
for (size_t i = 0; i < new_memo_size; i++) {
Py_XINCREF(unpickler->memo[i]);
new_memo[i] = unpickler->memo[i];
}
@@ -7060,8 +7061,7 @@ Unpickler_set_memo(UnpicklerObject *self, PyObject *obj)

error:
if (new_memo_size) {
i = new_memo_size;
while (--i >= 0) {
for (size_t i = new_memo_size - 1; i != SIZE_MAX; i--) {
Py_XDECREF(new_memo[i]);
}
PyMem_FREE(new_memo);

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