[Python-checkins] bpo-35552: Fix reading past the end in PyUnicode_FromFormat() and PyBytes_FromFormat(). (GH-11276)
Miss Islington (bot)
webhook-mailer at python.org
Sat Jan 12 03:52:59 EST 2019
https://github.com/python/cpython/commit/cbc7c2c791185ad44b4b3ede72309df5f252f4cb
commit: cbc7c2c791185ad44b4b3ede72309df5f252f4cb
branch: 3.7
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2019-01-12T00:52:55-08:00
summary:
bpo-35552: Fix reading past the end in PyUnicode_FromFormat() and PyBytes_FromFormat(). (GH-11276)
Format characters "%s" and "%V" in PyUnicode_FromFormat() and "%s" in PyBytes_FromFormat()
no longer read memory past the limit if precision is specified.
(cherry picked from commit d586ccb04f79863c819b212ec5b9d873964078e4)
Co-authored-by: Serhiy Storchaka <storchaka at gmail.com>
files:
A Misc/NEWS.d/next/Core and Builtins/2018-12-21-13-29-30.bpo-35552.1DzQQc.rst
M Objects/bytesobject.c
M Objects/unicodeobject.c
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-12-21-13-29-30.bpo-35552.1DzQQc.rst b/Misc/NEWS.d/next/Core and Builtins/2018-12-21-13-29-30.bpo-35552.1DzQQc.rst
new file mode 100644
index 000000000000..dbc00bcd75e9
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-12-21-13-29-30.bpo-35552.1DzQQc.rst
@@ -0,0 +1,3 @@
+Format characters ``%s`` and ``%V`` in :c:func:`PyUnicode_FromFormat` and
+``%s`` in :c:func:`PyBytes_FromFormat` no longer read memory past the
+limit if *precision* is specified.
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 5f9e1eccf2e4..172c7f38b9e2 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -311,9 +311,15 @@ PyBytes_FromFormatV(const char *format, va_list vargs)
Py_ssize_t i;
p = va_arg(vargs, const char*);
- i = strlen(p);
- if (prec > 0 && i > prec)
- i = prec;
+ if (prec <= 0) {
+ i = strlen(p);
+ }
+ else {
+ i = 0;
+ while (i < prec && p[i]) {
+ i++;
+ }
+ }
s = _PyBytesWriter_WriteBytes(&writer, s, p, i);
if (s == NULL)
goto error;
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 35c8a24b7c0c..b67ffac4e9fb 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -2579,9 +2579,15 @@ unicode_fromformat_write_cstr(_PyUnicodeWriter *writer, const char *str,
PyObject *unicode;
int res;
- length = strlen(str);
- if (precision != -1)
- length = Py_MIN(length, precision);
+ if (precision == -1) {
+ length = strlen(str);
+ }
+ else {
+ length = 0;
+ while (length < precision && str[length]) {
+ length++;
+ }
+ }
unicode = PyUnicode_DecodeUTF8Stateful(str, length, "replace", NULL);
if (unicode == NULL)
return -1;
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