ipv6: fix rtnl locking in setsockopt for anycast and multicast

Calling setsockopt with IPV6_JOIN_ANYCAST or IPV6_LEAVE_ANYCAST
triggers the assertion in addrconf_join_solict()/addrconf_leave_solict()

ipv6_sock_ac_join(), ipv6_sock_ac_drop(), ipv6_sock_ac_close() need to
take RTNL before calling ipv6_dev_ac_inc/dec. Same thing with
ipv6_sock_mc_join(), ipv6_sock_mc_drop(), ipv6_sock_mc_close() before
calling ipv6_dev_mc_inc/dec.

This patch moves ASSERT_RTNL() up a level in the call stack.

Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reported-by: Tommi Rantala <tt.rantala@gmail.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 0b239fc..aa0e135 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1690,14 +1690,12 @@
 	addrconf_mod_dad_work(ifp, 0);
 }
 
-/* Join to solicited addr multicast group. */
-
+/* Join to solicited addr multicast group.
+ * caller must hold RTNL */
 void addrconf_join_solict(struct net_device *dev, const struct in6_addr *addr)
 {
 	struct in6_addr maddr;
 
-	ASSERT_RTNL();
-
 	if (dev->flags&(IFF_LOOPBACK|IFF_NOARP))
 		return;
 
@@ -1705,12 +1703,11 @@
 	ipv6_dev_mc_inc(dev, &maddr);
 }
 
+/* caller must hold RTNL */
 void addrconf_leave_solict(struct inet6_dev *idev, const struct in6_addr *addr)
 {
 	struct in6_addr maddr;
 
-	ASSERT_RTNL();
-
 	if (idev->dev->flags&(IFF_LOOPBACK|IFF_NOARP))
 		return;
 
@@ -1718,12 +1715,11 @@
 	__ipv6_dev_mc_dec(idev, &maddr);
 }
 
+/* caller must hold RTNL */
 static void addrconf_join_anycast(struct inet6_ifaddr *ifp)
 {
 	struct in6_addr addr;
 
-	ASSERT_RTNL();
-
 	if (ifp->prefix_len >= 127) /* RFC 6164 */
 		return;
 	ipv6_addr_prefix(&addr, &ifp->addr, ifp->prefix_len);
@@ -1732,12 +1728,11 @@
 	ipv6_dev_ac_inc(ifp->idev->dev, &addr);
 }
 
+/* caller must hold RTNL */
 static void addrconf_leave_anycast(struct inet6_ifaddr *ifp)
 {
 	struct in6_addr addr;
 
-	ASSERT_RTNL();
-
 	if (ifp->prefix_len >= 127) /* RFC 6164 */
 		return;
 	ipv6_addr_prefix(&addr, &ifp->addr, ifp->prefix_len);