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>

3 files changed, 10 insertions, 15 deletions

diff --git a/net/wimax/op-msg.c b/net/wimax/op-msg.c
index f37dd3c5576d..c278b3356f75 100644
--- a/net/wimax/op-msg.c
+++ b/net/wimax/op-msg.c
@@ -279,8 +279,7 @@ int wimax_msg_send(struct wimax_dev *wimax_dev, struct sk_buff *skb)
 
         d_printf(1, dev, "CTX: wimax msg, %zu bytes\n", size);
         d_dump(2, dev, msg, size);
-        genlmsg_multicast(&wimax_gnl_family, skb, 0,
-                          wimax_gnl_mcg.id, GFP_KERNEL);
+        genlmsg_multicast(&wimax_gnl_family, skb, 0, 0, GFP_KERNEL);
         d_printf(1, dev, "CTX: genl multicast done\n");
         return 0;
 }
diff --git a/net/wimax/stack.c b/net/wimax/stack.c
index 18888748e699..ef2191b969a7 100644
--- a/net/wimax/stack.c
+++ b/net/wimax/stack.c
@@ -116,8 +116,9 @@ struct sk_buff *wimax_gnl_re_state_change_alloc(
                 dev_err(dev, "RE_STCH: can't create message\n");
                 goto error_new;
         }
-        data = genlmsg_put(report_skb, 0, wimax_gnl_mcg.id, &wimax_gnl_family,
-                           0, WIMAX_GNL_RE_STATE_CHANGE);
+        /* FIXME: sending a group ID as the seq is wrong */
+        data = genlmsg_put(report_skb, 0, wimax_gnl_family.mcgrp_offset,
+                           &wimax_gnl_family, 0, WIMAX_GNL_RE_STATE_CHANGE);
         if (data == NULL) {
                 dev_err(dev, "RE_STCH: can't put data into message\n");
                 goto error_put;
@@ -177,8 +178,7 @@ int wimax_gnl_re_state_change_send(
                 goto out;
         }
         genlmsg_end(report_skb, header);
-        genlmsg_multicast(&wimax_gnl_family, report_skb, 0,
-                          wimax_gnl_mcg.id, GFP_KERNEL);
+        genlmsg_multicast(&wimax_gnl_family, report_skb, 0, 0, GFP_KERNEL);
 out:
         d_fnend(3, dev, "(wimax_dev %p report_skb %p) = %d\n",
                 wimax_dev, report_skb, result);
@@ -580,8 +580,8 @@ struct genl_family wimax_gnl_family = {
         .maxattr = WIMAX_GNL_ATTR_MAX,
 };
 
-struct genl_multicast_group wimax_gnl_mcg = {
-        .name = "msg",
+static const struct genl_multicast_group wimax_gnl_mcgrps[] = {
+        { .name = "msg", },
 };
 
 
@@ -598,21 +598,18 @@ int __init wimax_subsys_init(void)
 
         snprintf(wimax_gnl_family.name, sizeof(wimax_gnl_family.name),
                  "WiMAX");
-        result = genl_register_family_with_ops(&wimax_gnl_family,
-                                               wimax_gnl_ops);
+        result = genl_register_family_with_ops_groups(&wimax_gnl_family,
+                                                      wimax_gnl_ops,
+                                                      wimax_gnl_mcgrps);
         if (unlikely(result < 0)) {
                 printk(KERN_ERR "cannot register generic netlink family: %d\n",
                        result);
                 goto error_register_family;
         }
 
-        result = genl_register_mc_group(&wimax_gnl_family, &wimax_gnl_mcg);
-        if (result < 0)
-                goto error_mc_group;
         d_fnend(4, NULL, "() = 0\n");
         return 0;
 
-error_mc_group:
         genl_unregister_family(&wimax_gnl_family);
 error_register_family:
         d_fnend(4, NULL, "() = %d\n", result);
diff --git a/net/wimax/wimax-internal.h b/net/wimax/wimax-internal.h
index 8567d3079a83..b445b82020a8 100644
--- a/net/wimax/wimax-internal.h
+++ b/net/wimax/wimax-internal.h
@@ -86,7 +86,6 @@ void wimax_rfkill_rm(struct wimax_dev *);
 
 /* generic netlink */
 extern struct genl_family wimax_gnl_family;
-extern struct genl_multicast_group wimax_gnl_mcg;
 
 /* ops */
 int wimax_gnl_doit_msg_from_user(struct sk_buff *skb, struct genl_info *info);