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, 19 insertions, 32 deletions

diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index 3092df313fb1..a9b2342d5253 100644
--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c
@@ -30,8 +30,8 @@
 #include "nfc.h"
 #include "llcp.h"
 
-static struct genl_multicast_group nfc_genl_event_mcgrp = {
-	.name = NFC_GENL_MCAST_EVENT_NAME,
+static const struct genl_multicast_group nfc_genl_mcgrps[] = {
+	{ .name = NFC_GENL_MCAST_EVENT_NAME, },
 };
 
 static struct genl_family nfc_genl_family = {
@@ -194,8 +194,7 @@ int nfc_genl_targets_found(struct nfc_dev *dev)
 
 	genlmsg_end(msg, hdr);
 
-	return genlmsg_multicast(&nfc_genl_family, msg, 0,
-				 nfc_genl_event_mcgrp.id, GFP_ATOMIC);
+	return genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_ATOMIC);
 
 nla_put_failure:
 	genlmsg_cancel(msg, hdr);
@@ -224,8 +223,7 @@ int nfc_genl_target_lost(struct nfc_dev *dev, u32 target_idx)
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
 
 	return 0;
 
@@ -257,8 +255,7 @@ int nfc_genl_tm_activated(struct nfc_dev *dev, u32 protocol)
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
 
 	return 0;
 
@@ -288,8 +285,7 @@ int nfc_genl_tm_deactivated(struct nfc_dev *dev)
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
 
 	return 0;
 
@@ -322,8 +318,7 @@ int nfc_genl_device_added(struct nfc_dev *dev)
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
 
 	return 0;
 
@@ -353,8 +348,7 @@ int nfc_genl_device_removed(struct nfc_dev *dev)
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
 
 	return 0;
 
@@ -420,8 +414,7 @@ int nfc_genl_llc_send_sdres(struct nfc_dev *dev, struct hlist_head *sdres_list)
 
 	genlmsg_end(msg, hdr);
 
-	return genlmsg_multicast(&nfc_genl_family, msg, 0,
-				 nfc_genl_event_mcgrp.id, GFP_ATOMIC);
+	return genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_ATOMIC);
 
 nla_put_failure:
 	genlmsg_cancel(msg, hdr);
@@ -455,8 +448,7 @@ int nfc_genl_se_added(struct nfc_dev *dev, u32 se_idx, u16 type)
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
 
 	return 0;
 
@@ -487,8 +479,7 @@ int nfc_genl_se_removed(struct nfc_dev *dev, u32 se_idx)
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
 
 	return 0;
 
@@ -609,8 +600,7 @@ int nfc_genl_dep_link_up_event(struct nfc_dev *dev, u32 target_idx,
 
 	dev->dep_link_up = true;
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_ATOMIC);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_ATOMIC);
 
 	return 0;
 
@@ -642,8 +632,7 @@ int nfc_genl_dep_link_down_event(struct nfc_dev *dev)
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_ATOMIC);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_ATOMIC);
 
 	return 0;
 
@@ -1148,8 +1137,7 @@ int nfc_genl_fw_download_done(struct nfc_dev *dev, const char *firmware_name,
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
 
 	return 0;
 
@@ -1320,8 +1308,7 @@ static void se_io_cb(void *context, u8 *apdu, size_t apdu_len, int err)
 
 	genlmsg_end(msg, hdr);
 
-	genlmsg_multicast(&nfc_genl_family, msg, 0,
-			  nfc_genl_event_mcgrp.id, GFP_KERNEL);
+	genlmsg_multicast(&nfc_genl_family, msg, 0, 0, GFP_KERNEL);
 
 	kfree(ctx);
 
@@ -1549,15 +1536,15 @@ int __init nfc_genl_init(void)
 {
 	int rc;
 
-	rc = genl_register_family_with_ops(&nfc_genl_family, nfc_genl_ops);
+	rc = genl_register_family_with_ops_groups(&nfc_genl_family,
+						  nfc_genl_ops,
+						  nfc_genl_mcgrps);
 	if (rc)
 		return rc;
 
-	rc = genl_register_mc_group(&nfc_genl_family, &nfc_genl_event_mcgrp);
-
 	netlink_register_notifier(&nl_notifier);
 
-	return rc;
+	return 0;
 }
 
 /**