Issue #14700: Fix two broken and undefined-behaviour-inducing overflow checks in old-style string formatting. Thanks Serhiy Storchaka for report and original patch.
diff --git a/Lib/test/string_tests.py b/Lib/test/string_tests.py
index b7246eb..eeeb457 100644
--- a/Lib/test/string_tests.py
+++ b/Lib/test/string_tests.py
@@ -1197,6 +1197,10 @@
self.checkraises(TypeError, '%10.*f', '__mod__', ('foo', 42.))
self.checkraises(ValueError, '%10', '__mod__', (42,))
+ # Outrageously large width or precision should raise ValueError.
+ self.checkraises(ValueError, '%%%df' % (2**64), '__mod__', (3.2))
+ self.checkraises(ValueError, '%%.%df' % (2**64), '__mod__', (3.2))
+
def test_floatformatting(self):
# float formatting
for prec in range(100):
diff --git a/Misc/NEWS b/Misc/NEWS
index 6047785..809114c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
Core and Builtins
-----------------
+- Issue #14700: Fix two broken and undefined-behaviour-inducing overflow checks
+ in old-style string formatting.
+
- Issue #14705: The PyArg_Parse() family of functions now support the 'p' format
unit, which accepts a "boolean predicate" argument. It converts any Python
value into an integer--0 if it is "false", and 1 otherwise.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index bb0d786..129a5fc 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -13933,7 +13933,7 @@
c = PyUnicode_READ(fmtkind, fmt, fmtpos++);
if (c < '0' || c > '9')
break;
- if ((width*10) / 10 != width) {
+ if (width > (PY_SSIZE_T_MAX - (c - '0')) / 10) {
PyErr_SetString(PyExc_ValueError,
"width too big");
goto onError;
@@ -13968,7 +13968,7 @@
c = PyUnicode_READ(fmtkind, fmt, fmtpos++);
if (c < '0' || c > '9')
break;
- if ((prec*10) / 10 != prec) {
+ if (prec > (INT_MAX - (c - '0')) / 10) {
PyErr_SetString(PyExc_ValueError,
"prec too big");
goto onError;