raise an OSError for invalid fds #4991

Lib/test/test_fileio.py

@@ -176,6 +176,10 @@ class OtherFileTests(unittest.TestCase):
         f.close()
         os.unlink(TESTFN)
 
+    def testInvalidFd(self):
+        self.assertRaises(ValueError, _fileio._FileIO, -10)
+        self.assertRaises(OSError, _fileio._FileIO, 10)
+
     def testBadModeArgument(self):
         # verify that we get a sensible error message for bad mode argument
         bad_mode = "qwerty"

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 2.7 alpha 1
 Core and Builtins
 -----------------
 
+- Issue #4991: Passing invalid file descriptors to io.FileIO now raises an
+  OSError.
+
 - Issue #4807: Port the _winreg module to Windows CE.
 
 - Issue #4935: The overflow checking code in the expandtabs() method common

Modules/_fileio.c

@@ -119,6 +119,24 @@ dircheck(PyFileIOObject* self, char *name)
 	return 0;
 }
 
+static int
+check_fd(int fd)
+{
+#if defined(HAVE_FSTAT)
+	struct stat buf;
+	if (fstat(fd, &buf) < 0 && errno == EBADF) {
+		PyObject *exc;
+		char *msg = strerror(EBADF);
+		exc = PyObject_CallFunction(PyExc_OSError, "(is)",
+					    EBADF, msg);
+		PyErr_SetObject(PyExc_OSError, exc);
+		Py_XDECREF(exc);
+		return -1;
+	}
+#endif
+	return 0;
+}
+
 
 static int
 fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
@@ -151,6 +169,8 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 					"Negative filedescriptor");
 			return -1;
 		}
+		if (check_fd(fd))
+			return -1;
 	}
 	else {
 		PyErr_Clear();