Merge branch 'genetlink_mcast'

Johannes Berg says:

====================
genetlink: clean up multicast group APIs

The generic netlink multicast group registration doesn't have to
be dynamic, and can thus be simplified just like I did with the
ops. This removes some complexity in registration code.

Additionally, two users of generic netlink already use multicast
groups in a wrong way, add workarounds for those two to keep the
userspace API working, but at the same time make them not clash
with other users of multicast groups as might happen now.

While making it all a bit easier, also prevent such abuse by adding
checks to the APIs so each family can only use the groups it owns.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 84 insertions, 54 deletions

diff --git a/include/linux/genl_magic_func.h b/include/linux/genl_magic_func.h
index 023bc346b877..c0894dd8827b 100644
--- a/include/linux/genl_magic_func.h
+++ b/include/linux/genl_magic_func.h
@@ -273,49 +273,40 @@ static struct genl_family ZZZ_genl_family __read_mostly = {
  * Magic: define multicast groups
  * Magic: define multicast group registration helper
  */
+#define ZZZ_genl_mcgrps		CONCAT_(GENL_MAGIC_FAMILY, _genl_mcgrps)
+static const struct genl_multicast_group ZZZ_genl_mcgrps[] = {
+#undef GENL_mc_group
+#define GENL_mc_group(group) { .name = #group, },
+#include GENL_MAGIC_INCLUDE_FILE
+};
+
+enum CONCAT_(GENL_MAGIC_FAMILY, group_ids) {
+#undef GENL_mc_group
+#define GENL_mc_group(group) CONCAT_(GENL_MAGIC_FAMILY, _group_ ## group),
+#include GENL_MAGIC_INCLUDE_FILE
+};
+
 #undef GENL_mc_group
 #define GENL_mc_group(group)						\
-static struct genl_multicast_group					\
-CONCAT_(GENL_MAGIC_FAMILY, _mcg_ ## group) __read_mostly = {		\
-	.name = #group,							\
-};									\
 static int CONCAT_(GENL_MAGIC_FAMILY, _genl_multicast_ ## group)(	\
 	struct sk_buff *skb, gfp_t flags)				\
 {									\
 	unsigned int group_id =						\
-		CONCAT_(GENL_MAGIC_FAMILY, _mcg_ ## group).id;	\
-	if (!group_id)							\
-		return -EINVAL;						\
-	return genlmsg_multicast(skb, 0, group_id, flags);		\
+		CONCAT_(GENL_MAGIC_FAMILY, _group_ ## group);		\
+	return genlmsg_multicast(&ZZZ_genl_family, skb, 0,		\
+				 group_id, flags);			\
 }
 
 #include GENL_MAGIC_INCLUDE_FILE
 
-int CONCAT_(GENL_MAGIC_FAMILY, _genl_register)(void)
-{
-	int err = genl_register_family_with_ops(&ZZZ_genl_family,
-		ZZZ_genl_ops, ARRAY_SIZE(ZZZ_genl_ops));
-	if (err)
-		return err;
-#undef GENL_mc_group
-#define GENL_mc_group(group)						\
-	err = genl_register_mc_group(&ZZZ_genl_family,			\
-		&CONCAT_(GENL_MAGIC_FAMILY, _mcg_ ## group));		\
-	if (err)							\
-		goto fail;						\
-	else								\
-		pr_info("%s: mcg %s: %u\n", #group,			\
-			__stringify(GENL_MAGIC_FAMILY),			\
-			CONCAT_(GENL_MAGIC_FAMILY, _mcg_ ## group).id);
-
-#include GENL_MAGIC_INCLUDE_FILE
-
 #undef GENL_mc_group
 #define GENL_mc_group(group)
-	return 0;
-fail:
-	genl_unregister_family(&ZZZ_genl_family);
-	return err;
+
+int CONCAT_(GENL_MAGIC_FAMILY, _genl_register)(void)
+{
+	return genl_register_family_with_ops_groups(&ZZZ_genl_family,	\
+						    ZZZ_genl_ops,	\
+						    ZZZ_genl_mcgrps);
 }
 
 void CONCAT_(GENL_MAGIC_FAMILY, _genl_unregister)(void)
diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index e96385d46b48..ace4abf118d7 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -10,16 +10,9 @@
 /**
  * struct genl_multicast_group - generic netlink multicast group
  * @name: name of the multicast group, names are per-family
- * @id: multicast group ID, assigned by the core, to use with
- *      genlmsg_multicast().
- * @list: list entry for linking
- * @family: pointer to family, need not be set before registering
  */
 struct genl_multicast_group {
-	struct genl_family	*family;	/* private */
-	struct list_head	list;		/* private */
 	char			name[GENL_NAMSIZ];
-	u32			id;
 };
 
 struct genl_ops;
@@ -40,7 +33,9 @@ struct genl_info;
  *	undo operations done by pre_doit, for example release locks
  * @attrbuf: buffer to store parsed attributes
  * @family_list: family list
- * @mcast_groups: multicast groups list
+ * @mcgrps: multicast groups used by this family (private)
+ * @n_mcgrps: number of multicast groups (private)
+ * @mcgrp_offset: starting number of multicast group IDs in this family
  * @ops: the operations supported by this family (private)
  * @n_ops: number of operations supported by this family (private)
  */
@@ -60,9 +55,11 @@ struct genl_family {
 					     struct genl_info *info);
 	struct nlattr **	attrbuf;	/* private */
 	const struct genl_ops *	ops;		/* private */
+	const struct genl_multicast_group *mcgrps; /* private */
 	unsigned int		n_ops;		/* private */
+	unsigned int		n_mcgrps;	/* private */
+	unsigned int		mcgrp_offset;	/* private */
 	struct list_head	family_list;	/* private */
-	struct list_head	mcast_groups;	/* private */
 	struct module		*module;
 };
 
@@ -152,21 +149,32 @@ static inline int genl_register_family(struct genl_family *family)
  *
  * Return 0 on success or a negative error code.
  */
-static inline int genl_register_family_with_ops(struct genl_family *family,
-	const struct genl_ops *ops, size_t n_ops)
+static inline int
+_genl_register_family_with_ops_grps(struct genl_family *family,
+				    const struct genl_ops *ops, size_t n_ops,
+				    const struct genl_multicast_group *mcgrps,
+				    size_t n_mcgrps)
 {
 	family->module = THIS_MODULE;
 	family->ops = ops;
 	family->n_ops = n_ops;
+	family->mcgrps = mcgrps;
+	family->n_mcgrps = n_mcgrps;
 	return __genl_register_family(family);
 }
 
+#define genl_register_family_with_ops(family, ops)			\
+	_genl_register_family_with_ops_grps((family),			\
+					    (ops), ARRAY_SIZE(ops),	\
+					    NULL, 0)
+#define genl_register_family_with_ops_groups(family, ops, grps)	\
+	_genl_register_family_with_ops_grps((family),			\
+					    (ops), ARRAY_SIZE(ops),	\
+					    (grps), ARRAY_SIZE(grps))
+
 int genl_unregister_family(struct genl_family *family);
-int genl_register_mc_group(struct genl_family *family,
-			   struct genl_multicast_group *grp);
-void genl_unregister_mc_group(struct genl_family *family,
-			      struct genl_multicast_group *grp);
-void genl_notify(struct sk_buff *skb, struct net *net, u32 portid,
+void genl_notify(struct genl_family *family,
+		 struct sk_buff *skb, struct net *net, u32 portid,
 		 u32 group, struct nlmsghdr *nlh, gfp_t flags);
 
 void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
@@ -246,41 +254,54 @@ static inline void genlmsg_cancel(struct sk_buff *skb, void *hdr)
 
 /**
  * genlmsg_multicast_netns - multicast a netlink message to a specific netns
+ * @family: the generic netlink family
  * @net: the net namespace
  * @skb: netlink message as socket buffer
  * @portid: own netlink portid to avoid sending to yourself
- * @group: multicast group id
+ * @group: offset of multicast group in groups array
  * @flags: allocation flags
  */
-static inline int genlmsg_multicast_netns(struct net *net, struct sk_buff *skb,
+static inline int genlmsg_multicast_netns(struct genl_family *family,
+					  struct net *net, struct sk_buff *skb,
 					  u32 portid, unsigned int group, gfp_t flags)
 {
+	if (group >= family->n_mcgrps)
+		return -EINVAL;
+	group = family->mcgrp_offset + group;
 	return nlmsg_multicast(net->genl_sock, skb, portid, group, flags);
 }
 
 /**
  * genlmsg_multicast - multicast a netlink message to the default netns
+ * @family: the generic netlink family
  * @skb: netlink message as socket buffer
  * @portid: own netlink portid to avoid sending to yourself
- * @group: multicast group id
+ * @group: offset of multicast group in groups array
  * @flags: allocation flags
  */
-static inline int genlmsg_multicast(struct sk_buff *skb, u32 portid,
+static inline int genlmsg_multicast(struct genl_family *family,
+				    struct sk_buff *skb, u32 portid,
 				    unsigned int group, gfp_t flags)
 {
-	return genlmsg_multicast_netns(&init_net, skb, portid, group, flags);
+	if (group >= family->n_mcgrps)
+		return -EINVAL;
+	group = family->mcgrp_offset + group;
+	return genlmsg_multicast_netns(family, &init_net, skb,
+				       portid, group, flags);
 }
 
 /**
  * genlmsg_multicast_allns - multicast a netlink message to all net namespaces
+ * @family: the generic netlink family
  * @skb: netlink message as socket buffer
  * @portid: own netlink portid to avoid sending to yourself
- * @group: multicast group id
+ * @group: offset of multicast group in groups array
  * @flags: allocation flags
  *
  * This function must hold the RTNL or rcu_read_lock().
  */
-int genlmsg_multicast_allns(struct sk_buff *skb, u32 portid,
+int genlmsg_multicast_allns(struct genl_family *family,
+			    struct sk_buff *skb, u32 portid,
 			    unsigned int group, gfp_t flags);
 
 /**
@@ -351,5 +372,22 @@ static inline struct sk_buff *genlmsg_new(size_t payload, gfp_t flags)
 	return nlmsg_new(genlmsg_total_size(payload), flags);
 }
 
+/**
+ * genl_set_err - report error to genetlink broadcast listeners
+ * @family: the generic netlink family
+ * @net: the network namespace to report the error to
+ * @portid: the PORTID of a process that we want to skip (if any)
+ * @group: the broadcast group that will notice the error
+ * 	(this is the offset of the multicast group in the groups array)
+ * @code: error code, must be negative (as usual in kernelspace)
+ *
+ * This function returns the number of broadcast listeners that have set the
+ * NETLINK_RECV_NO_ENOBUFS socket option.
+ */
+static inline int genl_set_err(struct genl_family *family, struct net *net,
+			       u32 portid, u32 group, int code)
+{
+	return netlink_set_err(net->genl_sock, portid, group, code);
+}
 
 #endif	/* __NET_GENERIC_NETLINK_H */
diff --git a/include/uapi/linux/genetlink.h b/include/uapi/linux/genetlink.h
index c880a417d8a9..1af72d8228e0 100644
--- a/include/uapi/linux/genetlink.h
+++ b/include/uapi/linux/genetlink.h
@@ -27,6 +27,7 @@ struct genlmsghdr {
  */
 #define GENL_ID_GENERATE	0
 #define GENL_ID_CTRL		NLMSG_MIN_TYPE
+#define GENL_ID_VFS_DQUOT	(NLMSG_MIN_TYPE + 1)
 
 /**************************************************************************
  * Controller