[3.13] gh-143195: fix UAF in `{bytearray,memoryview}.hex(sep)` via re-entrant `sep...

(cherry picked from commit 9976c2b6349a079ae39931d960b8c147e21c6c3f)

diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index cc0a46bb56e4ee7a2a1261ae7b4b53f5d78f67fa..3e948f3577977f67cc42e1e905d8effab663c6f2 100644 (file)
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -1929,6 +1929,19 @@ class ByteArrayTest(BaseBytesTest, unittest.TestCase):
         with self.assertRaises(BufferError):
             ba.rsplit(evil)
 
+    def test_hex_use_after_free(self):
+        # Prevent UAF in bytearray.hex(sep) with re-entrant sep.__len__.
+        # Regression test for https://github.com/python/cpython/issues/143195.
+        ba = bytearray(b'\xAA')
+
+        class S(bytes):
+            def __len__(self):
+                ba.clear()
+                return 1
+
+        self.assertRaises(BufferError, ba.hex, S(b':'))
+
+
 class AssortedBytesTest(unittest.TestCase):
     #
     # Test various combinations of bytes and bytearray

diff --git a/Lib/test/test_memoryview.py b/Lib/test/test_memoryview.py
index 69be0e5c82931f7e1df6d47ea7e9e40c1d97da65..91ae688978b0143f1a30d13b2c7505a614b9c1ab 100644 (file)
--- a/Lib/test/test_memoryview.py
+++ b/Lib/test/test_memoryview.py
@@ -399,6 +399,20 @@ class AbstractMemoryTests:
         self.assertEqual(c.format, "H")
         self.assertEqual(d.format, "H")
 
+    def test_hex_use_after_free(self):
+        # Prevent UAF in memoryview.hex(sep) with re-entrant sep.__len__.
+        # Regression test for https://github.com/python/cpython/issues/143195.
+        ba = bytearray(b'A' * 1024)
+        mv = memoryview(ba)
+
+        class S(bytes):
+            def __len__(self):
+                mv.release()
+                ba.clear()
+                return 1
+
+        self.assertRaises(BufferError, mv.hex, S(b':'))
+
 
 # Variations on source objects for the buffer: bytes-like objects, then arrays
 # with itemsize > 1.

diff --git a/Misc/NEWS.d/next/Core and Builtins/2025-12-27-10-14-26.gh-issue-143195.MNldfr.rst b/Misc/NEWS.d/next/Core and Builtins/2025-12-27-10-14-26.gh-issue-143195.MNldfr.rst
new file mode 100644 (file)
index 0000000..66dc5e2
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2025-12-27-10-14-26.gh-issue-143195.MNldfr.rst
@@ -0,0 +1,3 @@
+Fix use-after-free crashes in :meth:`bytearray.hex` and :meth:`memoryview.hex`
+when the separator's :meth:`~object.__len__` mutates the original object.
+Patch by Bénédikt Tran.

diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index f940e8c12546c78152266d659830e3208d256907..f4e4e2885d80bcd7e6e3357c46d2efd534203378 100644 (file)
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -2224,7 +2224,13 @@ bytearray_hex_impl(PyByteArrayObject *self, PyObject *sep, int bytes_per_sep)
 {
     char* argbuf = PyByteArray_AS_STRING(self);
     Py_ssize_t arglen = PyByteArray_GET_SIZE(self);
-    return _Py_strhex_with_sep(argbuf, arglen, sep, bytes_per_sep);
+    // Prevent 'self' from being freed if computing len(sep) mutates 'self'
+    // in _Py_strhex_with_sep().
+    // See: https://github.com/python/cpython/issues/143195.
+    self->ob_exports++;
+    PyObject *res = _Py_strhex_with_sep(argbuf, arglen, sep, bytes_per_sep);
+    self->ob_exports--;
+    return res;
 }
 
 static PyObject *

diff --git a/Objects/memoryobject.c b/Objects/memoryobject.c
index b1a58d6b40ed89128a6c553ccd2e6f366c9ba8c7..9773bc2cc1c98b4e9441a632410160425044580c 100644 (file)
--- a/Objects/memoryobject.c
+++ b/Objects/memoryobject.c
@@ -2330,7 +2330,13 @@ memoryview_hex_impl(PyMemoryViewObject *self, PyObject *sep,
     CHECK_RELEASED(self);
 
     if (MV_C_CONTIGUOUS(self->flags)) {
-        return _Py_strhex_with_sep(src->buf, src->len, sep, bytes_per_sep);
+        // Prevent 'self' from being freed if computing len(sep) mutates 'self'
+        // in _Py_strhex_with_sep().
+        // See: https://github.com/python/cpython/issues/143195.
+        self->exports++;
+        PyObject *ret = _Py_strhex_with_sep(src->buf, src->len, sep, bytes_per_sep);
+        self->exports--;
+        return ret;
     }
 
     bytes = PyBytes_FromStringAndSize(NULL, src->len);