[libvirt] [PATCHv3] python: Avoid memory leaks on libvirt_virNodeGetMemoryStats

From: Alex Jia <ajia@redhat.com> Detected by valgrind. Leaks are introduced in commit 17c7795. * python/libvirt-override.c (libvirt_virNodeGetMemoryStats): fix memory leaks and improve codes return value. For details, please see the following link: RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=770944 Signed-off-by: Alex Jia <ajia@redhat.com> --- python/libvirt-override.c | 46 ++++++++++++++++++++++++++++++-------------- 1 files changed, 31 insertions(+), 15 deletions(-) diff --git a/python/libvirt-override.c b/python/libvirt-override.c index 792cfa3..fb98627 100644 --- a/python/libvirt-override.c +++ b/python/libvirt-override.c @@ -2550,7 +2550,9 @@ libvirt_virNodeGetCPUStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) static PyObject * libvirt_virNodeGetMemoryStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) { - PyObject *ret; + PyObject *ret = NULL; + PyObject *key = NULL; + PyObject *val = NULL; PyObject *pyobj_conn; virConnectPtr conn; unsigned int flags; @@ -2559,39 +2561,53 @@ libvirt_virNodeGetMemoryStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args) virNodeMemoryStatsPtr stats = NULL; if (!PyArg_ParseTuple(args, (char *)"Oii:virNodeGetMemoryStats", &pyobj_conn, &cellNum, &flags)) - return(NULL); + return ret; conn = (virConnectPtr)(PyvirConnect_Get(pyobj_conn)); LIBVIRT_BEGIN_ALLOW_THREADS; c_retval = virNodeGetMemoryStats(conn, cellNum, NULL, &nparams, flags); LIBVIRT_END_ALLOW_THREADS; if (c_retval < 0) - return VIR_PY_NONE; + return ret; if (nparams) { if (VIR_ALLOC_N(stats, nparams) < 0) - return VIR_PY_NONE; + return PyErr_NoMemory(); LIBVIRT_BEGIN_ALLOW_THREADS; c_retval = virNodeGetMemoryStats(conn, cellNum, stats, &nparams, flags); LIBVIRT_END_ALLOW_THREADS; - if (c_retval < 0) { - VIR_FREE(stats); - return VIR_PY_NONE; - } - } - if (!(ret = PyDict_New())) { - VIR_FREE(stats); - return VIR_PY_NONE; + if (c_retval < 0) + goto error; } + + if (!(ret = PyDict_New())) + goto error; + for (i = 0; i < nparams; i++) { - PyDict_SetItem(ret, - libvirt_constcharPtrWrap(stats[i].field), - libvirt_ulonglongWrap(stats[i].value)); + key = libvirt_constcharPtrWrap(stats[i].field); + val = libvirt_ulonglongWrap(stats[i].value); + + if (!key || !val) + goto error; + + if (PyDict_SetItem(ret, key, val) < 0) { + Py_DECREF(ret); + goto error; + } + + Py_DECREF(key); + Py_DECREF(val); } VIR_FREE(stats); return ret; + +error: + VIR_FREE(stats); + Py_XDECREF(key); + Py_XDECREF(val); + return ret; } static PyObject * -- 1.7.1

On 17.02.2012 09:15, ajia@redhat.com wrote:
From: Alex Jia <ajia@redhat.com>
Detected by valgrind. Leaks are introduced in commit 17c7795.
* python/libvirt-override.c (libvirt_virNodeGetMemoryStats): fix memory leaks and improve codes return value.
For details, please see the following link: RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=770944
Signed-off-by: Alex Jia <ajia@redhat.com> --- python/libvirt-override.c | 46 ++++++++++++++++++++++++++++++-------------- 1 files changed, 31 insertions(+), 15 deletions(-)
ACK Michal

On 02/17/2012 01:15 AM, ajia@redhat.com wrote:
From: Alex Jia <ajia@redhat.com>
Detected by valgrind. Leaks are introduced in commit 17c7795.
* python/libvirt-override.c (libvirt_virNodeGetMemoryStats): fix memory leaks and improve codes return value.
For details, please see the following link: RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=770944
Signed-off-by: Alex Jia <ajia@redhat.com> --- python/libvirt-override.c | 46 ++++++++++++++++++++++++++++++-------------- 1 files changed, 31 insertions(+), 15 deletions(-)
LIBVIRT_BEGIN_ALLOW_THREADS; c_retval = virNodeGetMemoryStats(conn, cellNum, NULL, &nparams, flags); LIBVIRT_END_ALLOW_THREADS; if (c_retval < 0) - return VIR_PY_NONE; + return ret;
Wrong. At this point, ret is still NULL, but we really do want to return VIR_PY_NONE (we have a valid libvirt error, and not a python exception).
if (nparams) { if (VIR_ALLOC_N(stats, nparams) < 0) - return VIR_PY_NONE; + return PyErr_NoMemory();
Correct (here we have a python exception, not a libvirt error).
LIBVIRT_BEGIN_ALLOW_THREADS; c_retval = virNodeGetMemoryStats(conn, cellNum, stats, &nparams, flags); LIBVIRT_END_ALLOW_THREADS; - if (c_retval < 0) { - VIR_FREE(stats); - return VIR_PY_NONE; - } - } - if (!(ret = PyDict_New())) { - VIR_FREE(stats); - return VIR_PY_NONE; + if (c_retval < 0) + goto error;
Wrong - here's another place where we want to return VIR_PY_NONE.
} + + if (!(ret = PyDict_New())) + goto error;
Good - here we have a python exception, and ret is still NULL.
+ for (i = 0; i < nparams; i++) { - PyDict_SetItem(ret, - libvirt_constcharPtrWrap(stats[i].field), - libvirt_ulonglongWrap(stats[i].value)); + key = libvirt_constcharPtrWrap(stats[i].field); + val = libvirt_ulonglongWrap(stats[i].value); + + if (!key || !val) + goto error;
Hmm. Here, ret is allocated, so we mistakenly end up returning a python object when we really want to return NULL to cover the python error we just encountered.
+ + if (PyDict_SetItem(ret, key, val) < 0) { + Py_DECREF(ret); + goto error;
Even worse - we are allowing ret to be garbage collected, but still returning its address. If PyDict_SetItem fails, you want to return NULL, not the just-allocated dictionary object.
+ } + + Py_DECREF(key); + Py_DECREF(val); }
VIR_FREE(stats); return ret; + +error: + VIR_FREE(stats); + Py_XDECREF(key); + Py_XDECREF(val); + return ret;
I think we still need a v4 to fix things properly. -- Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
participants (3)
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ajia@redhat.com
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Eric Blake
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Michal Privoznik