Issue #29145: Fix overflow checks in string, bytearray and unicode.
Patch by jan matejek and Xiang Zhang.
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index 4e38735..9b93898 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -2358,31 +2358,30 @@
{
char *self_s, *result_s;
Py_ssize_t self_len, result_len;
- Py_ssize_t count, i, product;
+ Py_ssize_t count, i;
PyStringObject *result;
self_len = PyString_GET_SIZE(self);
- /* 1 at the end plus 1 after every character */
- count = self_len+1;
- if (maxcount < count)
+ /* 1 at the end plus 1 after every character;
+ count = min(maxcount, self_len + 1) */
+ if (maxcount <= self_len) {
count = maxcount;
+ }
+ else {
+ /* Can't overflow: self_len + 1 <= maxcount <= PY_SSIZE_T_MAX. */
+ count = self_len + 1;
+ }
/* Check for overflow */
/* result_len = count * to_len + self_len; */
- product = count * to_len;
- if (product / to_len != count) {
+ assert(count > 0);
+ if (to_len > (PY_SSIZE_T_MAX - self_len) / count) {
PyErr_SetString(PyExc_OverflowError,
"replace string is too long");
return NULL;
}
- result_len = product + self_len;
- if (result_len < 0) {
- PyErr_SetString(PyExc_OverflowError,
- "replace string is too long");
- return NULL;
- }
-
+ result_len = count * to_len + self_len;
if (! (result = (PyStringObject *)
PyString_FromStringAndSize(NULL, result_len)) )
return NULL;
@@ -2610,7 +2609,7 @@
char *self_s, *result_s;
char *start, *next, *end;
Py_ssize_t self_len, result_len;
- Py_ssize_t count, product;
+ Py_ssize_t count;
PyStringObject *result;
self_s = PyString_AS_STRING(self);
@@ -2624,16 +2623,12 @@
/* use the difference between current and new, hence the "-1" */
/* result_len = self_len + count * (to_len-1) */
- product = count * (to_len-1);
- if (product / (to_len-1) != count) {
+ assert(count > 0);
+ if (to_len - 1 > (PY_SSIZE_T_MAX - self_len) / count) {
PyErr_SetString(PyExc_OverflowError, "replace string is too long");
return NULL;
}
- result_len = self_len + product;
- if (result_len < 0) {
- PyErr_SetString(PyExc_OverflowError, "replace string is too long");
- return NULL;
- }
+ result_len = self_len + count * (to_len - 1);
if ( (result = (PyStringObject *)
PyString_FromStringAndSize(NULL, result_len)) == NULL)
@@ -2676,7 +2671,7 @@
char *self_s, *result_s;
char *start, *next, *end;
Py_ssize_t self_len, result_len;
- Py_ssize_t count, offset, product;
+ Py_ssize_t count, offset;
PyStringObject *result;
self_s = PyString_AS_STRING(self);
@@ -2693,16 +2688,12 @@
/* Check for overflow */
/* result_len = self_len + count * (to_len-from_len) */
- product = count * (to_len-from_len);
- if (product / (to_len-from_len) != count) {
+ assert(count > 0);
+ if (to_len - from_len > (PY_SSIZE_T_MAX - self_len) / count) {
PyErr_SetString(PyExc_OverflowError, "replace string is too long");
return NULL;
}
- result_len = self_len + product;
- if (result_len < 0) {
- PyErr_SetString(PyExc_OverflowError, "replace string is too long");
- return NULL;
- }
+ result_len = self_len + count * (to_len - from_len);
if ( (result = (PyStringObject *)
PyString_FromStringAndSize(NULL, result_len)) == NULL)