genetlink: make multicast groups const, prevent abuse

Register generic netlink multicast groups as an array with
the family and give them contiguous group IDs. Then instead
of passing the global group ID to the various functions that
send messages, pass the ID relative to the family - for most
families that's just 0 because the only have one group.

This avoids the list_head and ID in each group, adding a new
field for the mcast group ID offset to the family.

At the same time, this allows us to prevent abusing groups
again like the quota and dropmon code did, since we can now
check that a family only uses a group it owns.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 13 deletions

diff --git a/net/hsr/hsr_netlink.c b/net/hsr/hsr_netlink.c
index 0009416c08c2..5325af85eea6 100644
--- a/net/hsr/hsr_netlink.c
+++ b/net/hsr/hsr_netlink.c
@@ -90,8 +90,8 @@ static struct genl_family hsr_genl_family = {
         .maxattr = HSR_A_MAX,
 };
 
-static struct genl_multicast_group hsr_network_genl_mcgrp = {
-        .name = "hsr-network",
+static const struct genl_multicast_group hsr_mcgrps[] = {
+        { .name = "hsr-network", },
 };
 
 
@@ -129,8 +129,7 @@ void hsr_nl_ringerror(struct hsr_priv *hsr_priv, unsigned char addr[ETH_ALEN],
                 goto nla_put_failure;
 
         genlmsg_end(skb, msg_head);
-        genlmsg_multicast(&hsr_genl_family, skb, 0,
-                          hsr_network_genl_mcgrp.id, GFP_ATOMIC);
+        genlmsg_multicast(&hsr_genl_family, skb, 0, 0, GFP_ATOMIC);
 
         return;
 
@@ -164,8 +163,7 @@ void hsr_nl_nodedown(struct hsr_priv *hsr_priv, unsigned char addr[ETH_ALEN])
                 goto nla_put_failure;
 
         genlmsg_end(skb, msg_head);
-        genlmsg_multicast(&hsr_genl_family, skb, 0,
-                          hsr_network_genl_mcgrp.id, GFP_ATOMIC);
+        genlmsg_multicast(&hsr_genl_family, skb, 0, 0, GFP_ATOMIC);
 
         return;
 
@@ -416,18 +414,13 @@ int __init hsr_netlink_init(void)
         if (rc)
                 goto fail_rtnl_link_register;
 
-        rc = genl_register_family_with_ops(&hsr_genl_family, hsr_ops);
+        rc = genl_register_family_with_ops_groups(&hsr_genl_family, hsr_ops,
+                                                  hsr_mcgrps);
         if (rc)
                 goto fail_genl_register_family;
 
-        rc = genl_register_mc_group(&hsr_genl_family, &hsr_network_genl_mcgrp);
-        if (rc)
-                goto fail_genl_register_mc_group;
-
         return 0;
 
-fail_genl_register_mc_group:
-        genl_unregister_family(&hsr_genl_family);
 fail_genl_register_family:
         rtnl_link_unregister(&hsr_link_ops);
 fail_rtnl_link_register: