net: Add checking to rcu_dereference() primitives

Update rcu_dereference() primitives to use new lockdep-based
checking. The rcu_dereference() in __in6_dev_get() may be
protected either by rcu_read_lock() or RTNL, per Eric Dumazet.
The rcu_dereference() in __sk_free() is protected by the fact
that it is never reached if an update could change it.  Check
for this by using rcu_dereference_check() to verify that the
struct sock's ->sk_wmem_alloc counter is zero.

Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1266887105-1528-5-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 6 insertions, 1 deletions

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 05330fc5b436..5c52fa43785c 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -735,6 +735,9 @@ extern void rtnl_lock(void);
 extern void rtnl_unlock(void);
 extern int rtnl_trylock(void);
 extern int rtnl_is_locked(void);
+#ifdef CONFIG_PROVE_LOCKING
+extern int lockdep_rtnl_is_held(void);
+#endif /* #ifdef CONFIG_PROVE_LOCKING */
 
 extern void rtnetlink_init(void);
 extern void __rtnl_unlock(void);
diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 0f7c37825fc1..45375b41a2a0 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -177,7 +177,9 @@ extern int unregister_inet6addr_notifier(struct notifier_block *nb);
 static inline struct inet6_dev *
 __in6_dev_get(struct net_device *dev)
 {
-        return rcu_dereference(dev->ip6_ptr);
+        return rcu_dereference_check(dev->ip6_ptr,
+                                     rcu_read_lock_held() ||
+                                     lockdep_rtnl_is_held());
 }
 
 static inline struct inet6_dev *