There's an overflow in nsswitch/winbind_nss_aix.c:843

  ret[n] = NULL;

which was detected by running an application with MALLOCDEBUG=catch_overflow. The array is allocated as

  n = sizeof(attr_list) / sizeof(struct attr_types);
  size = (n*sizeof(attrlist_t *));
  if ( (ret = malloc( size )) == NULL ) ...

Guess the array should be allocated with

  size = ((n + 1) * sizeof(attrlist_t *));