netlink: Properly unbind in error conditions.

Even if netlink_kernel_cfg::unbind is implemented the unbind() method is
not called, because cfg->unbind is omitted in __netlink_kernel_create().
And fix wrong argument of test_bit() and off by one problem.

At this point, no unbind() method is implemented, so there is no real
issue.

Fixes: 4f520900522f ("netlink: have netlink per-protocol bind function return an error code.")
Signed-off-by: Hiroaki SHIMODA <shimoda.hiroaki@gmail.com>
Cc: Richard Guy Briggs <rgb@redhat.com>
Acked-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/af_netlink.c

@@ -1440,7 +1440,7 @@ static void netlink_unbind(int group, long unsigned int groups,
 		return;
 
 	for (undo = 0; undo < group; undo++)
-		if (test_bit(group, &groups))
+		if (test_bit(undo, &groups))
 			nlk->netlink_unbind(undo);
 }
 
@@ -1492,7 +1492,7 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
 			netlink_insert(sk, net, nladdr->nl_pid) :
 			netlink_autobind(sock);
 		if (err) {
-			netlink_unbind(nlk->ngroups - 1, groups, nlk);
+			netlink_unbind(nlk->ngroups, groups, nlk);
 			return err;
 		}
 	}
@@ -2509,6 +2509,7 @@ __netlink_kernel_create(struct net *net, int unit, struct module *module,
 		nl_table[unit].module = module;
 		if (cfg) {
 			nl_table[unit].bind = cfg->bind;
+			nl_table[unit].unbind = cfg->unbind;
 			nl_table[unit].flags = cfg->flags;
 			if (cfg->compare)
 				nl_table[unit].compare = cfg->compare;