PL/Python: Fix potential NULL pointer dereference

After d0aa965c0a0ac2ff7906ae1b1dad50a7952efa56, one error path in
PLy_spi_execute_fetch_result() could result in the variable "result"
being dereferenced after being set to NULL.  Rearrange the code a bit to
fix that.

Also add another SPI_freetuptable() call so that that is cleared in all
error paths.

discovered by John Naylor <jcnaylor@gmail.com> via scan-build

ideas and review by Tom Lane

diff --git a/src/pl/plpython/plpy_spi.c b/src/pl/plpython/plpy_spi.c
index ade27f3924210b2f8a622762e53ade0f4ad0f64f..0c623a945814690d7bab2e353dd4522b28e15d73 100644 (file)
--- a/src/pl/plpython/plpy_spi.c
+++ b/src/pl/plpython/plpy_spi.c
@@ -361,7 +361,10 @@ PLy_spi_execute_fetch_result(SPITupleTable *tuptable, uint64 rows, int status)
 
        result = (PLyResultObject *) PLy_result_new();
        if (!result)
+       {
+               SPI_freetuptable(tuptable);
                return NULL;
+       }
        Py_DECREF(result->status);
        result->status = PyInt_FromLong(status);
 
@@ -411,12 +414,7 @@ PLy_spi_execute_fetch_result(SPITupleTable *tuptable, uint64 rows, int status)
 
                                Py_DECREF(result->rows);
                                result->rows = PyList_New(rows);
-                               if (!result->rows)
-                               {
-                                       Py_DECREF(result);
-                                       result = NULL;
-                               }
-                               else
+                               if (result->rows)
                                {
                                        PLy_input_setup_tuple(&ininfo, tuptable->tupdesc,
                                                                                  exec_ctx->curr_proc);
@@ -455,6 +453,13 @@ PLy_spi_execute_fetch_result(SPITupleTable *tuptable, uint64 rows, int status)
 
                MemoryContextDelete(cxt);
                SPI_freetuptable(tuptable);
+
+               /* in case PyList_New() failed above */
+               if (!result->rows)
+               {
+                       Py_DECREF(result);
+                       result = NULL;
+               }
        }
 
        return (PyObject *) result;