netfilter: Zero the tuple in nfnl_cthelper_parse_tuple()
nfnl_cthelper_parse_tuple() is called from nfnl_cthelper_new(),
nfnl_cthelper_get() and nfnl_cthelper_del(). In each case they pass
a pointer to an nf_conntrack_tuple data structure local variable:
struct nf_conntrack_tuple tuple;
...
ret = nfnl_cthelper_parse_tuple(&tuple, tb[NFCTH_TUPLE]);
The problem is that this local variable is not initialized, and
nfnl_cthelper_parse_tuple() only initializes two fields: src.l3num and
dst.protonum. This leaves all other fields with undefined values
based on whatever is on the stack: