[bug report] ASoC: audio-graph-card2: add Codec2Codec support

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Kuninori Morimoto,

Commit c3a15c92a67b ("ASoC: audio-graph-card2: add Codec2Codec
support") from Oct 12, 2021 (linux-next), leads to the following
Smatch static checker warning:

	sound/soc/generic/audio-graph-card2.c:1206 graph_count_c2c()
	warn: already decremented on line 1206 'lnk->kobj.kref.refcount.refs.counter'

sound/soc/generic/audio-graph-card2.c
    1194 static int graph_count_c2c(struct simple_util_priv *priv,
    1195                            struct device_node *lnk,
    1196                            struct link_info *li)
    1197 {
    1198         struct device_node *ports = of_get_parent(lnk);
    1199         struct device_node *port0 = lnk;
    1200         struct device_node *port1 = of_get_next_child(ports, lnk);
                                                                      ^^^

This calls of_node_put() on lnk.

    1201         struct device_node *ep0 = port_to_endpoint(port0);
    1202         struct device_node *ep1 = port_to_endpoint(port1);
    1203         struct device_node *codec0 = of_graph_get_remote_port(ep0);
    1204         struct device_node *codec1 = of_graph_get_remote_port(ep1);
    1205 
--> 1206         of_node_get(lnk);

So this of_node_get() undoes the put.  But if the reference count
dropped to zero then this would be a use afer free.

    1207 
    1208         /*
    1209          * codec2codec {
    1210          *        ports {
    1211          * =>        lnk:        port@0 { endpoint { ... }; };
    1212          *                port@1 { endpoint { ... }; };
    1213          *        };
    1214          * };
    1215          */
    1216         /*
    1217          * DON'T REMOVE platforms
    1218          * see
    1219          *        simple-card.c :: simple_count_noml()
    1220          */
    1221         li->num[li->link].cpus                =
    1222         li->num[li->link].platforms        = graph_counter(codec0);
    1223 
    1224         li->num[li->link].codecs        = graph_counter(codec1);
    1225 
    1226         of_node_put(ports);
    1227         of_node_put(port1);
    1228         of_node_put(ep0);
    1229         of_node_put(ep1);
    1230         of_node_put(codec0);
    1231         of_node_put(codec1);
    1232 
    1233         return 0;
    1234 }

regards,
dan carpenter