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Fix memory ownership and allocation handling #21

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Merged
bluecmd merged 1 commit into from
Jul 23, 2026
Merged

Fix memory ownership and allocation handling #21

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54 changes: 41 additions & 13 deletions netsnmp/client_intf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1919,7 +1919,7 @@ netsnmp_walk(PyObject *self, PyObject *args)
netsnmp_session *ss;
netsnmp_pdu *pdu, *response;
netsnmp_pdu *newpdu;
netsnmp_variable_list *vars, *oldvars;
netsnmp_variable_list *vars;
struct tree *tp;
int len;
oid **oid_arr = NULL;
Expand Down Expand Up @@ -1984,6 +1984,11 @@ netsnmp_walk(PyObject *self, PyObject *args)

pdu = snmp_pdu_create(SNMP_MSG_GETNEXT);

if (!pdu) {
PyErr_NoMemory();
goto done;
}

/* we need an initial count for memory allocation */
varlist_iter = PyObject_GetIter(varlist);
varlist_len = 0;
Expand All @@ -1998,11 +2003,24 @@ netsnmp_walk(PyObject *self, PyObject *args)
oid_arr = calloc(varlist_len, sizeof(oid *));
oid_arr_broken_check = calloc(varlist_len, sizeof(oid *));

if (varlist_len && (!oid_arr_len || !oid_arr_broken_check_len ||
!oid_arr || !oid_arr_broken_check)) {
PyErr_NoMemory();
snmp_free_pdu(pdu);
goto done;
}

for(varlist_ind = 0; varlist_ind < varlist_len; varlist_ind++) {

oid_arr[varlist_ind] = calloc(MAX_OID_LEN, sizeof(oid));
oid_arr_broken_check[varlist_ind] = calloc(MAX_OID_LEN, sizeof(oid));

if (!oid_arr[varlist_ind] || !oid_arr_broken_check[varlist_ind]) {
PyErr_NoMemory();
snmp_free_pdu(pdu);
goto done;
}

oid_arr_len[varlist_ind] = MAX_OID_LEN;
oid_arr_broken_check_len[varlist_ind] = MAX_OID_LEN;
}
Expand Down Expand Up @@ -2109,8 +2127,6 @@ netsnmp_walk(PyObject *self, PyObject *args)
vars != NULL;
vars = vars->next_variable, varlist_ind++) {

oid_arr_broken_check[varlist_ind] = calloc(MAX_OID_LEN, sizeof(oid));

oid_arr_broken_check_len[varlist_ind] = vars->name_length;
memcpy(oid_arr_broken_check[varlist_ind],
vars->name, vars->name_length * sizeof(oid));
Expand All @@ -2129,12 +2145,17 @@ netsnmp_walk(PyObject *self, PyObject *args)
} else {
newpdu = snmp_pdu_create(SNMP_MSG_GETNEXT);

if (!newpdu) {
PyErr_NoMemory();
snmp_free_pdu(response);
response = NULL;
break;
}

for(vars = (response ? response->variables : NULL),
varlist_ind = 0,
oldvars = (pdu ? pdu->variables : NULL);
varlist_ind = 0;
vars && (varlist_ind < varlist_len);
vars = vars->next_variable, varlist_ind++,
oldvars = (oldvars ? oldvars->next_variable : NULL)) {
vars = vars->next_variable, varlist_ind++) {

if ((vars->name_length < oid_arr_len[varlist_ind]) ||
(memcmp(oid_arr[varlist_ind], vars->name,
Expand Down Expand Up @@ -2228,7 +2249,10 @@ application.
snmp_add_null_var(newpdu, vars->name,
vars->name_length);
}
pdu = newpdu;
if (notdone)
pdu = newpdu;
else
snmp_free_pdu(newpdu);
}
if (response)
snmp_free_pdu(response);
Expand All @@ -2244,20 +2268,24 @@ application.
/* propagate error */
if (verbose)
printf("error: walk response processing: unknown python error");
Py_DECREF(val_tuple);
Py_CLEAR(val_tuple);
}
}

done:
Py_XDECREF(varbinds);
SAFE_FREE(oid_arr_len);
SAFE_FREE(oid_arr_broken_check_len);
for(varlist_ind = 0; varlist_ind < varlist_len; varlist_ind ++) {
SAFE_FREE(oid_arr[varlist_ind]);
SAFE_FREE(oid_arr_broken_check[varlist_ind]);
}
if (oid_arr)
for(varlist_ind = 0; varlist_ind < varlist_len; varlist_ind ++)
SAFE_FREE(oid_arr[varlist_ind]);
if (oid_arr_broken_check)
for(varlist_ind = 0; varlist_ind < varlist_len; varlist_ind ++)
SAFE_FREE(oid_arr_broken_check[varlist_ind]);
SAFE_FREE(oid_arr);
SAFE_FREE(oid_arr_broken_check);
if (PyErr_Occurred())
return NULL;
return (val_tuple ? val_tuple : Py_BuildValue(""));
}

Expand Down
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