net: Revert "ipv4: fix a deadlock in ip_ra_control"

This reverts commit 1215e51edad1.
Since raw_close() is used on every RAW socket destruction,
the changes made by 1215e51edad1 scale sadly. This clearly
seen on endless unshare(CLONE_NEWNET) test, and cleanup_net()
kwork spends a lot of time waiting for rtnl_lock() introduced
by this commit.

Previous patch moved IP_ROUTER_ALERT out of rtnl_lock(),
so we revert this patch.

Signed-off-by: Kirill Tkhai <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/ip_sockglue.c

···
 	case MCAST_LEAVE_GROUP:
 	case MCAST_LEAVE_SOURCE_GROUP:
 	case MCAST_UNBLOCK_SOURCE:
-	case IP_ROUTER_ALERT:
 		return true;
 	}
 	return false;

net/ipv4/ipmr.c

···
 	struct net *net = sock_net(sk);
 	struct mr_table *mrt;
 
-	ASSERT_RTNL();
+	rtnl_lock();
 	ipmr_for_each_table(mrt, net) {
 		if (sk == rtnl_dereference(mrt->mroute_sk)) {
 			IPV4_DEVCONF_ALL(net, MC_FORWARDING)--;
···
 			mroute_clean_tables(mrt, false);
 		}
 	}
+	rtnl_unlock();
 }
 
 /* Socket options and virtual interface manipulation. The whole
···
 		if (sk != rcu_access_pointer(mrt->mroute_sk)) {
 			ret = -EACCES;
 		} else {
+			/* We need to unlock here because mrtsock_destruct takes
+			 * care of rtnl itself and we can't change that due to
+			 * the IP_ROUTER_ALERT setsockopt which runs without it.
+			 */
+			rtnl_unlock();
 			ret = ip_ra_control(sk, 0, NULL);
-			goto out_unlock;
+			goto out;
 		}
 		break;
 	case MRT_ADD_VIF:
···
 	}
 out_unlock:
 	rtnl_unlock();
+out:
 	return ret;
 }
 

net/ipv4/raw.c

···
 	/*
 	 * Raw sockets may have direct kernel references. Kill them.
 	 */
-	rtnl_lock();
 	ip_ra_control(sk, 0, NULL);
-	rtnl_unlock();
 
 	sk_common_release(sk);
 }