link: link_msg_parser(): keep link info instead of release and reacquire

Calling release_link_info() will call io_free() for rtnl_link::l_info
was allocated just a few lines before as a side effect of
rtnl_link_set_type().

Apart from doing needless memory churn, this will also leave the link
with l_info set to NULL if the link type does not provide a io_parse()
function.

Assuming the memory leak mentioned in bfee88b ("route: fix memory
leak of l_info_ops in link_msg_parser()") was a double reference taken
by calling rtnl_link_info_ops_lookup() twice, once via
rtnl_link_set_type(), and once directly, replace the lookup() /
release() lookup() with a single lookup() and then reuse the populated
rtnl_link::l_info_ops pointer.

Fixes: bfee88b ("route: fix memory leak of l_info_ops in link_msg_parser()")
Signed-off-by: Jonas Gorski <[email protected]>

lib/route/link.c

@@ -681,11 +681,7 @@ static int link_msg_parser(struct nl_cache_ops *ops, struct sockaddr_nl *who,
 					tb[IFLA_PROTINFO] = (struct nlattr *)link->l_af_ops->ao_protinfo_policy;
 			}
 
-			if (link->l_info_ops)
-				release_link_info(link);
-
-			ops = rtnl_link_info_ops_lookup(kind);
-			link->l_info_ops = ops;
+			ops = link->l_info_ops;
 
 			if (ops) {
 				if (ops->io_parse &&