2 files changed, 33 insertions, 23 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index d0ff382c40ca..c5aab6a368ce 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -177,9 +177,11 @@ static void netlink_sock_destruct(struct sock *sk)
  * this, _but_ remember, it adds useless work on UP machines.
  */
 
-static void netlink_table_grab(void)
+void netlink_table_grab(void)
         __acquires(nl_table_lock)
 {
+        might_sleep();
+
         write_lock_irq(&nl_table_lock);
 
         if (atomic_read(&nl_table_users)) {
@@ -200,7 +202,7 @@ static void netlink_table_grab(void)
         }
 }
 
-static void netlink_table_ungrab(void)
+void netlink_table_ungrab(void)
         __releases(nl_table_lock)
 {
         write_unlock_irq(&nl_table_lock);
@@ -1549,37 +1551,21 @@ static void netlink_free_old_listeners(struct rcu_head *rcu_head)
         kfree(lrh->ptr);
 }
 
-/**
- * netlink_change_ngroups - change number of multicast groups
- *
- * This changes the number of multicast groups that are available
- * on a certain netlink family. Note that it is not possible to
- * change the number of groups to below 32. Also note that it does
- * not implicitly call netlink_clear_multicast_users() when the
- * number of groups is reduced.
- *
- * @sk: The kernel netlink socket, as returned by netlink_kernel_create().
- * @groups: The new number of groups.
- */
-int netlink_change_ngroups(struct sock *sk, unsigned int groups)
+int __netlink_change_ngroups(struct sock *sk, unsigned int groups)
 {
         unsigned long *listeners, *old = NULL;
         struct listeners_rcu_head *old_rcu_head;
         struct netlink_table *tbl = &nl_table[sk->sk_protocol];
-        int err = 0;
 
         if (groups < 32)
                 groups = 32;
 
-        netlink_table_grab();
         if (NLGRPSZ(tbl->groups) < NLGRPSZ(groups)) {
                 listeners = kzalloc(NLGRPSZ(groups) +
                                     sizeof(struct listeners_rcu_head),
                                     GFP_ATOMIC);
-                if (!listeners) {
-                        err = -ENOMEM;
-                        goto out_ungrab;
-                }
+                if (!listeners)
+                        return -ENOMEM;
                 old = tbl->listeners;
                 memcpy(listeners, old, NLGRPSZ(tbl->groups));
                 rcu_assign_pointer(tbl->listeners, listeners);
@@ -1597,8 +1583,29 @@ int netlink_change_ngroups(struct sock *sk, unsigned int groups)
         }
         tbl->groups = groups;
 
- out_ungrab:
+        return 0;
+}
+
+/**
+ * netlink_change_ngroups - change number of multicast groups
+ *
+ * This changes the number of multicast groups that are available
+ * on a certain netlink family. Note that it is not possible to
+ * change the number of groups to below 32. Also note that it does
+ * not implicitly call netlink_clear_multicast_users() when the
+ * number of groups is reduced.
+ *
+ * @sk: The kernel netlink socket, as returned by netlink_kernel_create().
+ * @groups: The new number of groups.
+ */
+int netlink_change_ngroups(struct sock *sk, unsigned int groups)
+{
+        int err;
+
+        netlink_table_grab();
+        err = __netlink_change_ngroups(sk, groups);
         netlink_table_ungrab();
+
         return err;
 }
 
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 66f6ba0bab11..566941e03363 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -176,9 +176,10 @@ int genl_register_mc_group(struct genl_family *family,
         if (family->netnsok) {
                 struct net *net;
 
+                netlink_table_grab();
                 rcu_read_lock();
                 for_each_net_rcu(net) {
-                        err = netlink_change_ngroups(net->genl_sock,
+                        err = __netlink_change_ngroups(net->genl_sock,
                                         mc_groups_longs * BITS_PER_LONG);
                         if (err) {
                                 /*
@@ -188,10 +189,12 @@ int genl_register_mc_group(struct genl_family *family,
                                  * increased on some sockets which is ok.
                                  */
                                 rcu_read_unlock();
+                                netlink_table_ungrab();
                                 goto out;
                         }
                 }
                 rcu_read_unlock();
+                netlink_table_ungrab();
         } else {
                 err = netlink_change_ngroups(init_net.genl_sock,
                                              mc_groups_longs * BITS_PER_LONG);