python · gst · Jul 29, 2022
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-07-29-09-52-22.gh-issue-95380.p8S_K0.rst b/Misc/NEWS.d/next/Core and Builtins/2022-07-29-09-52-22.gh-issue-95380.p8S_K0.rst
@@ -0,0 +1 @@
+Remove max path size limit of 1024 for :func:`fcntl.fcntl` function. Patch by Grégory Starck.
diff --git a/Modules/clinic/fcntlmodule.c.h b/Modules/clinic/fcntlmodule.c.h
diff --git a/Modules/fcntlmodule.c b/Modules/fcntlmodule.c
@@ -40,21 +40,19 @@ as constants in the fcntl module, using the same names as used in
 the relevant C header files.  The argument arg is optional, and
 defaults to 0; it may be an int or a string.  If arg is given as a string,
 the return value of fcntl is a string of that length, containing the
-resulting value put in the arg buffer by the operating system.  The length
-of the arg string is not allowed to exceed 1024 bytes.  If the arg given
+resulting value put in the arg buffer by the operating system.  If the arg given
 is an integer or if none is specified, the result value is an integer
 corresponding to the return value of the fcntl call in the C code.
 [clinic start generated code]*/
 
 static PyObject *
 fcntl_fcntl_impl(PyObject *module, int fd, int code, PyObject *arg)
-/*[clinic end generated code: output=888fc93b51c295bd input=7955340198e5f334]*/
+/*[clinic end generated code: output=888fc93b51c295bd input=eed7ab9999c13350]*/
 {
     unsigned int int_arg = 0;
     int ret;
     char *str;
     Py_ssize_t len;
-    char buf[1024];
     int async_err = 0;
 
     if (PySys_Audit("fcntl.fcntl", "iiO", fd, code, arg ? arg : Py_None) < 0) {
@@ -65,21 +63,23 @@ fcntl_fcntl_impl(PyObject *module, int fd, int code, PyObject *arg)
         int parse_result;
 
         if (PyArg_Parse(arg, "s#", &str, &len)) {
-            if ((size_t)len > sizeof buf) {
-                PyErr_SetString(PyExc_ValueError,
-                                "fcntl string arg too long");
+            PyObject* buf_ret = PyBytes_FromStringAndSize(NULL, len);
+            if (buf_ret == NULL) {
+                PyErr_NoMemory();
                 return NULL;
             }
+            char *buf = PyBytes_AS_STRING(buf_ret);
             memcpy(buf, str, len);
             do {
                 Py_BEGIN_ALLOW_THREADS
                 ret = fcntl(fd, code, buf);
                 Py_END_ALLOW_THREADS
             } while (ret == -1 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
             if (ret < 0) {
+                Py_DECREF(buf_ret);
                 return !async_err ? PyErr_SetFromErrno(PyExc_OSError) : NULL;
             }
-            return PyBytes_FromStringAndSize(buf, len);
+            return buf_ret;
         }
 
         PyErr_Clear();
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Remove max path size limit of 1024 for :func:`fcntl.fcntl` function. Patch by Grégory Starck.