ipv4: fib: Send notification before deleting FIB alias

When a FIB alias is replaced following NLM_F_REPLACE, the ENTRY_ADD
notification is sent after the reference on the previous FIB info was
dropped. This is problematic as potential listeners might need to access
it in their notification blocks.

Solve this by sending the notification prior to the deletion of the
replaced FIB alias. This is consistent with ENTRY_DEL notifications.
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
CC: Patrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/fib_trie.c

@@ -1295,6 +1295,13 @@ int fib_table_insert(struct net *net, struct fib_table *tb,
 			new_fa->tb_id = tb->tb_id;
 			new_fa->fa_default = -1;
 
+			call_fib_entry_notifiers(net, FIB_EVENT_ENTRY_ADD,
+						 key, plen, fi,
+						 new_fa->fa_tos, cfg->fc_type,
+						 tb->tb_id, nlflags);
+			rtmsg_fib(RTM_NEWROUTE, htonl(key), new_fa, plen,
+				  tb->tb_id, &cfg->fc_nlinfo, nlflags);
+
 			hlist_replace_rcu(&fa->fa_list, &new_fa->fa_list);
 
 			alias_free_mem_rcu(fa);
@@ -1303,13 +1310,6 @@ int fib_table_insert(struct net *net, struct fib_table *tb,
 			if (state & FA_S_ACCESSED)
 				rt_cache_flush(cfg->fc_nlinfo.nl_net);
 
-			call_fib_entry_notifiers(net, FIB_EVENT_ENTRY_ADD,
-						 key, plen, fi,
-						 new_fa->fa_tos, cfg->fc_type,
-						 tb->tb_id, cfg->fc_nlflags);
-			rtmsg_fib(RTM_NEWROUTE, htonl(key), new_fa, plen,
-				tb->tb_id, &cfg->fc_nlinfo, nlflags);
-
 			goto succeeded;
 		}
 		/* Error if we find a perfect match which