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>

9 files changed, 35 insertions, 21 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 *
diff --git a/net/core/dev.c b/net/core/dev.c
index ec874218b206..bb1f1da2b8a7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2041,7 +2041,7 @@ gso:
         rcu_read_lock_bh();
 
         txq = dev_pick_tx(dev, skb);
-        q = rcu_dereference(txq->qdisc);
+        q = rcu_dereference_bh(txq->qdisc);
 
 #ifdef CONFIG_NET_CLS_ACT
         skb->tc_verd = SET_TC_AT(skb->tc_verd, AT_EGRESS);
diff --git a/net/core/filter.c b/net/core/filter.c
index 08db7b9143a3..3541aa48d21d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -86,7 +86,7 @@ int sk_filter(struct sock *sk, struct sk_buff *skb)
                 return err;
 
         rcu_read_lock_bh();
-        filter = rcu_dereference(sk->sk_filter);
+        filter = rcu_dereference_bh(sk->sk_filter);
         if (filter) {
                 unsigned int pkt_len = sk_run_filter(skb, filter->insns,
                                 filter->len);
@@ -521,7 +521,7 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
         }
 
         rcu_read_lock_bh();
-        old_fp = rcu_dereference(sk->sk_filter);
+        old_fp = rcu_dereference_bh(sk->sk_filter);
         rcu_assign_pointer(sk->sk_filter, fp);
         rcu_read_unlock_bh();
 
@@ -536,7 +536,7 @@ int sk_detach_filter(struct sock *sk)
         struct sk_filter *filter;
 
         rcu_read_lock_bh();
-        filter = rcu_dereference(sk->sk_filter);
+        filter = rcu_dereference_bh(sk->sk_filter);
         if (filter) {
                 rcu_assign_pointer(sk->sk_filter, NULL);
                 sk_filter_delayed_uncharge(sk, filter);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 794bcb897ff0..4c7d3f635ba7 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -89,6 +89,14 @@ int rtnl_is_locked(void)
 }
 EXPORT_SYMBOL(rtnl_is_locked);
 
+#ifdef CONFIG_PROVE_LOCKING
+int lockdep_rtnl_is_held(void)
+{
+        return lockdep_is_held(&rtnl_mutex);
+}
+EXPORT_SYMBOL(lockdep_rtnl_is_held);
+#endif /* #ifdef CONFIG_PROVE_LOCKING */
+
 static struct rtnl_link *rtnl_msg_handlers[NPROTO];
 
 static inline int rtm_msgindex(int msgtype)
diff --git a/net/core/sock.c b/net/core/sock.c
index e1f6f225f012..305cba401ae6 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1073,7 +1073,8 @@ static void __sk_free(struct sock *sk)
         if (sk->sk_destruct)
                 sk->sk_destruct(sk);
 
-        filter = rcu_dereference(sk->sk_filter);
+        filter = rcu_dereference_check(sk->sk_filter,
+                                       atomic_read(&sk->sk_wmem_alloc) == 0);
         if (filter) {
                 sk_filter_uncharge(sk, filter);
                 rcu_assign_pointer(sk->sk_filter, NULL);
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index a03284061a31..a7bf03ca0a36 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -1155,8 +1155,8 @@ static int __dn_route_output_key(struct dst_entry **pprt, const struct flowi *fl
 
         if (!(flags & MSG_TRYHARD)) {
                 rcu_read_lock_bh();
-                for(rt = rcu_dereference(dn_rt_hash_table[hash].chain); rt;
-                        rt = rcu_dereference(rt->u.dst.dn_next)) {
+                for (rt = rcu_dereference_bh(dn_rt_hash_table[hash].chain); rt;
+                        rt = rcu_dereference_bh(rt->u.dst.dn_next)) {
                         if ((flp->fld_dst == rt->fl.fld_dst) &&
                             (flp->fld_src == rt->fl.fld_src) &&
                             (flp->mark == rt->fl.mark) &&
@@ -1618,9 +1618,9 @@ int dn_cache_dump(struct sk_buff *skb, struct netlink_callback *cb)
                 if (h > s_h)
                         s_idx = 0;
                 rcu_read_lock_bh();
-                for(rt = rcu_dereference(dn_rt_hash_table[h].chain), idx = 0;
+                for(rt = rcu_dereference_bh(dn_rt_hash_table[h].chain), idx = 0;
                         rt;
-                        rt = rcu_dereference(rt->u.dst.dn_next), idx++) {
+                        rt = rcu_dereference_bh(rt->u.dst.dn_next), idx++) {
                         if (idx < s_idx)
                                 continue;
                         skb_dst_set(skb, dst_clone(&rt->u.dst));
@@ -1654,12 +1654,12 @@ static struct dn_route *dn_rt_cache_get_first(struct seq_file *seq)
 
         for(s->bucket = dn_rt_hash_mask; s->bucket >= 0; --s->bucket) {
                 rcu_read_lock_bh();
-                rt = dn_rt_hash_table[s->bucket].chain;
+                rt = rcu_dereference_bh(dn_rt_hash_table[s->bucket].chain);
                 if (rt)
                         break;
                 rcu_read_unlock_bh();
         }
-        return rcu_dereference(rt);
+        return rt;
 }
 
 static struct dn_route *dn_rt_cache_get_next(struct seq_file *seq, struct dn_route *rt)
@@ -1674,7 +1674,7 @@ static struct dn_route *dn_rt_cache_get_next(struct seq_file *seq, struct dn_rou
                 rcu_read_lock_bh();
                 rt = dn_rt_hash_table[s->bucket].chain;
         }
-        return rcu_dereference(rt);
+        return rcu_dereference_bh(rt);
 }
 
 static void *dn_rt_cache_seq_start(struct seq_file *seq, loff_t *pos)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index d62b05d33384..4f11faa5c824 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -287,12 +287,12 @@ static struct rtable *rt_cache_get_first(struct seq_file *seq)
                 if (!rt_hash_table[st->bucket].chain)
                         continue;
                 rcu_read_lock_bh();
-                r = rcu_dereference(rt_hash_table[st->bucket].chain);
+                r = rcu_dereference_bh(rt_hash_table[st->bucket].chain);
                 while (r) {
                         if (dev_net(r->u.dst.dev) == seq_file_net(seq) &&
                             r->rt_genid == st->genid)
                                 return r;
-                        r = rcu_dereference(r->u.dst.rt_next);
+                        r = rcu_dereference_bh(r->u.dst.rt_next);
                 }
                 rcu_read_unlock_bh();
         }
@@ -314,7 +314,7 @@ static struct rtable *__rt_cache_get_next(struct seq_file *seq,
                 rcu_read_lock_bh();
                 r = rt_hash_table[st->bucket].chain;
         }
-        return rcu_dereference(r);
+        return rcu_dereference_bh(r);
 }
 
 static struct rtable *rt_cache_get_next(struct seq_file *seq,
@@ -2689,8 +2689,8 @@ int __ip_route_output_key(struct net *net, struct rtable **rp,
         hash = rt_hash(flp->fl4_dst, flp->fl4_src, flp->oif, rt_genid(net));
 
         rcu_read_lock_bh();
-        for (rth = rcu_dereference(rt_hash_table[hash].chain); rth;
-                rth = rcu_dereference(rth->u.dst.rt_next)) {
+        for (rth = rcu_dereference_bh(rt_hash_table[hash].chain); rth;
+                rth = rcu_dereference_bh(rth->u.dst.rt_next)) {
                 if (rth->fl.fl4_dst == flp->fl4_dst &&
                     rth->fl.fl4_src == flp->fl4_src &&
                     rth->fl.iif == 0 &&
@@ -3008,8 +3008,8 @@ int ip_rt_dump(struct sk_buff *skb,  struct netlink_callback *cb)
                 if (!rt_hash_table[h].chain)
                         continue;
                 rcu_read_lock_bh();
-                for (rt = rcu_dereference(rt_hash_table[h].chain), idx = 0; rt;
-                     rt = rcu_dereference(rt->u.dst.rt_next), idx++) {
+                for (rt = rcu_dereference_bh(rt_hash_table[h].chain), idx = 0; rt;
+                     rt = rcu_dereference_bh(rt->u.dst.rt_next), idx++) {
                         if (!net_eq(dev_net(rt->u.dst.dev), net) || idx < s_idx)
                                 continue;
                         if (rt_is_expired(rt))
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index f126d18dbdc4..939471ef8d50 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -508,7 +508,7 @@ static inline unsigned int run_filter(struct sk_buff *skb, struct sock *sk,
         struct sk_filter *filter;
 
         rcu_read_lock_bh();
-        filter = rcu_dereference(sk->sk_filter);
+        filter = rcu_dereference_bh(sk->sk_filter);
         if (filter != NULL)
                 res = sk_run_filter(skb, filter->insns, filter->len);
         rcu_read_unlock_bh();