From a4ae828ee416a66d8c7bf5ee71d653c2cc6a26dd Mon Sep 17 00:00:00 2001 From: Benjamin Peterson Date: Thu, 20 Sep 2018 18:36:40 -0700 Subject: [PATCH] closes bpo-34656: Avoid relying on signed overflow in _pickle memos. (GH-9261) --- Modules/_pickle.c | 62 +++++++++++++++++++++++------------------------ 1 file changed, 31 insertions(+), 31 deletions(-) diff --git a/Modules/_pickle.c b/Modules/_pickle.c index 2de70f5d9405dc..3588e33f097165 100644 --- a/Modules/_pickle.c +++ b/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);