Issue #10383: Fix two leaks.

Modules/posixmodule.c

@@ -5620,8 +5620,10 @@ posix_read(PyObject *self, PyObject *args)
     buffer = PyBytes_FromStringAndSize((char *)NULL, size);
     if (buffer == NULL)
         return NULL;
-    if (!_PyVerify_fd(fd))
+    if (!_PyVerify_fd(fd)) {
+        Py_DECREF(buffer);
         return posix_error();
+    }
     Py_BEGIN_ALLOW_THREADS
     n = read(fd, PyBytes_AS_STRING(buffer), size);
     Py_END_ALLOW_THREADS
@@ -5648,8 +5650,10 @@ posix_write(PyObject *self, PyObject *args)
 
     if (!PyArg_ParseTuple(args, "iy*:write", &fd, &pbuf))
         return NULL;
-    if (!_PyVerify_fd(fd))
+    if (!_PyVerify_fd(fd)) {
+        PyBuffer_Release(&pbuf);
         return posix_error();
+    }
     Py_BEGIN_ALLOW_THREADS
     size = write(fd, pbuf.buf, (size_t)pbuf.len);
     Py_END_ALLOW_THREADS