[libvirt] [libvirt-python PATCH] fix leak in memoryStats with older python

[Martin Kletzander]

libvirt_virDomainMemoryStats() function creates a dictionary without
any checks whether the additions were successful, whether the python
objects were created and, most importantly, without decrementing the
reference count on the objects added to the dictionary.  This is
somehow not an issue with current upstream versions, however with
python 2.6 this exposes a leak in our bindings.  The following patch
works on both old and new CPython versions and is already used in
other parts of the code, so it's also most straightforward.

Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
---
 libvirt-override.c | 68 +++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 44 insertions(+), 24 deletions(-)

diff --git a/libvirt-override.c b/libvirt-override.c
index a7a6213..8fd856b 100644
--- a/libvirt-override.c
+++ b/libvirt-override.c
@@ -734,6 +734,7 @@ libvirt_virDomainMemoryStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
     size_t i;
     virDomainMemoryStatStruct stats[VIR_DOMAIN_MEMORY_STAT_NR];
     PyObject *info;
+    PyObject *key = NULL, *val = NULL;

     if (!PyArg_ParseTuple(args, (char *)"O:virDomainMemoryStats", &pyobj_domain))
         return NULL;
@@ -749,31 +750,50 @@ libvirt_virDomainMemoryStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) {
         return VIR_PY_NONE;

     for (i = 0; i < nr_stats; i++) {
-        if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_SWAP_IN)
-            PyDict_SetItem(info, libvirt_constcharPtrWrap("swap_in"),
-                           libvirt_ulonglongWrap(stats[i].val));
-        else if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_SWAP_OUT)
-            PyDict_SetItem(info, libvirt_constcharPtrWrap("swap_out"),
-                           libvirt_ulonglongWrap(stats[i].val));
-        else if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_MAJOR_FAULT)
-            PyDict_SetItem(info, libvirt_constcharPtrWrap("major_fault"),
-                           libvirt_ulonglongWrap(stats[i].val));
-        else if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_MINOR_FAULT)
-            PyDict_SetItem(info, libvirt_constcharPtrWrap("minor_fault"),
-                           libvirt_ulonglongWrap(stats[i].val));
-        else if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_UNUSED)
-            PyDict_SetItem(info, libvirt_constcharPtrWrap("unused"),
-                           libvirt_ulonglongWrap(stats[i].val));
-        else if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_AVAILABLE)
-            PyDict_SetItem(info, libvirt_constcharPtrWrap("available"),
-                           libvirt_ulonglongWrap(stats[i].val));
-        else if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON)
-            PyDict_SetItem(info, libvirt_constcharPtrWrap("actual"),
-                           libvirt_ulonglongWrap(stats[i].val));
-        else if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_RSS)
-            PyDict_SetItem(info, libvirt_constcharPtrWrap("rss"),
-                           libvirt_ulonglongWrap(stats[i].val));
+        switch (stats[i].tag) {
+        case VIR_DOMAIN_MEMORY_STAT_SWAP_IN:
+            key = libvirt_constcharPtrWrap("swap_in");
+            break;
+        case VIR_DOMAIN_MEMORY_STAT_SWAP_OUT:
+            key = libvirt_constcharPtrWrap("swap_out");
+            break;
+        case VIR_DOMAIN_MEMORY_STAT_MAJOR_FAULT:
+            key = libvirt_constcharPtrWrap("major_fault");
+            break;
+        case VIR_DOMAIN_MEMORY_STAT_MINOR_FAULT:
+            key = libvirt_constcharPtrWrap("minor_fault");
+            break;
+        case VIR_DOMAIN_MEMORY_STAT_UNUSED:
+            key = libvirt_constcharPtrWrap("unused");
+            break;
+        case VIR_DOMAIN_MEMORY_STAT_AVAILABLE:
+            key = libvirt_constcharPtrWrap("available");
+            break;
+        case VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON:
+            key = libvirt_constcharPtrWrap("actual");
+            break;
+        case VIR_DOMAIN_MEMORY_STAT_RSS:
+            key = libvirt_constcharPtrWrap("rss");
+            break;
+        default:
+            continue;
+        }
+        val = libvirt_ulonglongWrap(stats[i].val);
+
+        if (!key || !val || PyDict_SetItem(info, key, val) < 0) {
+            Py_DECREF(info);
+            info = NULL;
+            goto cleanup;
+        }
+        Py_DECREF(key);
+        Py_DECREF(val);
+        key = NULL;
+        val = NULL;
     }
+
+ cleanup:
+    Py_XDECREF(key);
+    Py_XDECREF(val);
     return info;
 }

-- 
1.9.3