Issue #23796: peak and read1 methods of BufferedReader now raise ValueError

if they called on a closed object.

Patch by John Hergenroeder.

Lib/test/test_io.py

@@ -1191,6 +1191,14 @@ class BufferedReaderTest(unittest.TestCase, CommonBufferedTests):
             self.assertEqual(rawio._extraneous_reads, 0,
                              "failed for {}: {} != 0".format(n, rawio._extraneous_reads))
 
+    def test_read_on_closed(self):
+        # Issue #23796
+        b = io.BufferedReader(io.BytesIO(b"12"))
+        b.read(1)
+        b.close()
+        self.assertRaises(ValueError, b.peek)
+        self.assertRaises(ValueError, b.read1, 1)
+
 
 class CBufferedReaderTest(BufferedReaderTest, SizeofTest):
     tp = io.BufferedReader

Misc/NEWS

@@ -40,6 +40,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #23796: peak and read1 methods of BufferedReader now raise ValueError
+  if they called on a closed object. Patch by John Hergenroeder.
+
 - Issue #21795: smtpd now supports the 8BITMIME extension whenever
   the new *decode_data* constructor argument is set to False.
 

Modules/_io/bufferedio.c

@@ -871,6 +871,8 @@ _io__Buffered_peek_impl(buffered *self, Py_ssize_t size)
     PyObject *res = NULL;
 
     CHECK_INITIALIZED(self)
+    CHECK_CLOSED(self, "peek of closed file")
+
     if (!ENTER_BUFFERED(self))
         return NULL;
 
@@ -947,6 +949,9 @@ _io__Buffered_read1_impl(buffered *self, Py_ssize_t n)
                         "read length must be positive");
         return NULL;
     }
+
+    CHECK_CLOSED(self, "read of closed file")
+
     if (n == 0)
         return PyBytes_FromStringAndSize(NULL, 0);