net: move fib_rules_unregister() under rtnl lock

We have to hold rtnl lock for fib_rules_unregister()
otherwise the following race could happen:

fib_rules_unregister():	fib_nl_delrule():
...				...
...				ops = lookup_rules_ops();
list_del_rcu(&ops->list);
				list_for_each_entry(ops->rules) {
fib_rules_cleanup_ops(ops);	  ...
  list_del_rcu();		  list_del_rcu();
				}

Note, net->rules_mod_lock is actually not needed at all,
either upper layer netns code or rtnl lock guarantees
we are safe.

Cc: Alexander Duyck <alexander.h.duyck@redhat.com>
Cc: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 8 insertions, 5 deletions

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 44706e81b2e0..e4fdc9dfb2c7 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -175,9 +175,9 @@ void fib_rules_unregister(struct fib_rules_ops *ops)
 
         spin_lock(&net->rules_mod_lock);
         list_del_rcu(&ops->list);
-        fib_rules_cleanup_ops(ops);
         spin_unlock(&net->rules_mod_lock);
 
+        fib_rules_cleanup_ops(ops);
         call_rcu(&ops->rcu, fib_rules_put_rcu);
 }
 EXPORT_SYMBOL_GPL(fib_rules_unregister);
diff --git a/net/decnet/dn_rules.c b/net/decnet/dn_rules.c
index faf7cc3483fe..9d66a0f72f90 100644
--- a/net/decnet/dn_rules.c
+++ b/net/decnet/dn_rules.c
@@ -248,7 +248,9 @@ void __init dn_fib_rules_init(void)
 
 void __exit dn_fib_rules_cleanup(void)
 {
+        rtnl_lock();
         fib_rules_unregister(dn_fib_rules_ops);
+        rtnl_unlock();
         rcu_barrier();
 }
 
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 57be71dd6a9e..23b9b3e86f4c 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1111,11 +1111,10 @@ static void ip_fib_net_exit(struct net *net)
 {
         unsigned int i;
 
+        rtnl_lock();
 #ifdef CONFIG_IP_MULTIPLE_TABLES
         fib4_rules_exit(net);
 #endif
-
-        rtnl_lock();
         for (i = 0; i < FIB_TABLE_HASHSZ; i++) {
                 struct fib_table *tb;
                 struct hlist_head *head;
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index bc40115bc394..fe54eba6d00d 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -283,8 +283,8 @@ static void __net_exit ipmr_rules_exit(struct net *net)
                 list_del(&mrt->list);
                 ipmr_free_table(mrt);
         }
-        rtnl_unlock();
         fib_rules_unregister(net->ipv4.mr_rules_ops);
+        rtnl_unlock();
 }
 #else
 #define ipmr_for_each_table(mrt, net) \
diff --git a/net/ipv6/fib6_rules.c b/net/ipv6/fib6_rules.c
index 27ca79682efb..70bc6abc0639 100644
--- a/net/ipv6/fib6_rules.c
+++ b/net/ipv6/fib6_rules.c
@@ -322,7 +322,9 @@ out_fib6_rules_ops:
 
 static void __net_exit fib6_rules_net_exit(struct net *net)
 {
+        rtnl_lock();
         fib_rules_unregister(net->ipv6.fib6_rules_ops);
+        rtnl_unlock();
 }
 
 static struct pernet_operations fib6_rules_net_ops = {
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 52028f449a89..2f1fd9ffcb34 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -267,8 +267,8 @@ static void __net_exit ip6mr_rules_exit(struct net *net)
                 list_del(&mrt->list);
                 ip6mr_free_table(mrt);
         }
-        rtnl_unlock();
         fib_rules_unregister(net->ipv6.mr6_rules_ops);
+        rtnl_unlock();
 }
 #else
 #define ip6mr_for_each_table(mrt, net) \