11 files changed, 60 insertions, 61 deletions

diff --git a/include/net/dst.h b/include/net/dst.h
index ce078cda6b74..aac5a5fcfda9 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -225,21 +225,6 @@ static inline void dst_confirm(struct dst_entry *dst)
                 neigh_confirm(dst->neighbour);
 }
 
-static inline void dst_negative_advice(struct dst_entry **dst_p,
-                                       struct sock *sk)
-{
-        struct dst_entry * dst = *dst_p;
-        if (dst && dst->ops->negative_advice) {
-                *dst_p = dst->ops->negative_advice(dst);
-
-                if (dst != *dst_p) {
-                        extern void sk_reset_txq(struct sock *sk);
-
-                        sk_reset_txq(sk);
-                }
-        }
-}
-
 static inline void dst_link_failure(struct sk_buff *skb)
 {
         struct dst_entry *dst = skb_dst(skb);
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 68f67836e146..278312c95f96 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -152,9 +152,9 @@ static inline void __ip6_dst_store(struct sock *sk, struct dst_entry *dst,
 static inline void ip6_dst_store(struct sock *sk, struct dst_entry *dst,
                                  struct in6_addr *daddr, struct in6_addr *saddr)
 {
-        write_lock(&sk->sk_dst_lock);
+        spin_lock(&sk->sk_dst_lock);
         __ip6_dst_store(sk, dst, daddr, saddr);
-        write_unlock(&sk->sk_dst_lock);
+        spin_unlock(&sk->sk_dst_lock);
 }
 
 static inline int ipv6_unicast_destination(struct sk_buff *skb)
diff --git a/include/net/sock.h b/include/net/sock.h
index b4603cd54fcd..56df440a950b 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -262,7 +262,7 @@ struct sock {
 #ifdef CONFIG_XFRM
         struct xfrm_policy      *sk_policy[2];
 #endif
-        rwlock_t                sk_dst_lock;
+        spinlock_t              sk_dst_lock;
         atomic_t                sk_rmem_alloc;
         atomic_t                sk_wmem_alloc;
         atomic_t                sk_omem_alloc;
@@ -1192,7 +1192,8 @@ extern unsigned long sock_i_ino(struct sock *sk);
 static inline struct dst_entry *
 __sk_dst_get(struct sock *sk)
 {
-        return sk->sk_dst_cache;
+        return rcu_dereference_check(sk->sk_dst_cache, rcu_read_lock_held() ||
+                                                       sock_owned_by_user(sk));
 }
 
 static inline struct dst_entry *
@@ -1200,50 +1201,62 @@ sk_dst_get(struct sock *sk)
 {
         struct dst_entry *dst;
 
-        read_lock(&sk->sk_dst_lock);
-        dst = sk->sk_dst_cache;
+        rcu_read_lock();
+        dst = rcu_dereference(sk->sk_dst_cache);
         if (dst)
                 dst_hold(dst);
-        read_unlock(&sk->sk_dst_lock);
+        rcu_read_unlock();
         return dst;
 }
 
+extern void sk_reset_txq(struct sock *sk);
+
+static inline void dst_negative_advice(struct sock *sk)
+{
+        struct dst_entry *ndst, *dst = __sk_dst_get(sk);
+
+        if (dst && dst->ops->negative_advice) {
+                ndst = dst->ops->negative_advice(dst);
+
+                if (ndst != dst) {
+                        rcu_assign_pointer(sk->sk_dst_cache, ndst);
+                        sk_reset_txq(sk);
+                }
+        }
+}
+
 static inline void
 __sk_dst_set(struct sock *sk, struct dst_entry *dst)
 {
         struct dst_entry *old_dst;
 
         sk_tx_queue_clear(sk);
-        old_dst = sk->sk_dst_cache;
-        sk->sk_dst_cache = dst;
+        old_dst = rcu_dereference_check(sk->sk_dst_cache,
+                                        lockdep_is_held(&sk->sk_dst_lock));
+        rcu_assign_pointer(sk->sk_dst_cache, dst);
         dst_release(old_dst);
 }
 
 static inline void
 sk_dst_set(struct sock *sk, struct dst_entry *dst)
 {
-        write_lock(&sk->sk_dst_lock);
+        spin_lock(&sk->sk_dst_lock);
         __sk_dst_set(sk, dst);
-        write_unlock(&sk->sk_dst_lock);
+        spin_unlock(&sk->sk_dst_lock);
 }
 
 static inline void
 __sk_dst_reset(struct sock *sk)
 {
-        struct dst_entry *old_dst;
-
-        sk_tx_queue_clear(sk);
-        old_dst = sk->sk_dst_cache;
-        sk->sk_dst_cache = NULL;
-        dst_release(old_dst);
+        __sk_dst_set(sk, NULL);
 }
 
 static inline void
 sk_dst_reset(struct sock *sk)
 {
-        write_lock(&sk->sk_dst_lock);
+        spin_lock(&sk->sk_dst_lock);
         __sk_dst_reset(sk);
-        write_unlock(&sk->sk_dst_lock);
+        spin_unlock(&sk->sk_dst_lock);
 }
 
 extern struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie);
diff --git a/net/core/dev.c b/net/core/dev.c
index 0eb79e35671f..ca4cdef74a1b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2015,7 +2015,7 @@ static struct netdev_queue *dev_pick_tx(struct net_device *dev,
                         if (dev->real_num_tx_queues > 1)
                                 queue_index = skb_tx_hash(dev, skb);
 
-                        if (sk && sk->sk_dst_cache)
+                        if (sk && rcu_dereference_check(sk->sk_dst_cache, 1))
                                 sk_tx_queue_set(sk, queue_index);
                 }
         }
diff --git a/net/core/sock.c b/net/core/sock.c
index c5812bbc2cc9..7effa1e689df 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -364,11 +364,11 @@ EXPORT_SYMBOL(sk_reset_txq);
 
 struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie)
 {
-        struct dst_entry *dst = sk->sk_dst_cache;
+        struct dst_entry *dst = __sk_dst_get(sk);
 
         if (dst && dst->obsolete && dst->ops->check(dst, cookie) == NULL) {
                 sk_tx_queue_clear(sk);
-                sk->sk_dst_cache = NULL;
+                rcu_assign_pointer(sk->sk_dst_cache, NULL);
                 dst_release(dst);
                 return NULL;
         }
@@ -1157,7 +1157,7 @@ struct sock *sk_clone(const struct sock *sk, const gfp_t priority)
                 skb_queue_head_init(&newsk->sk_async_wait_queue);
 #endif
 
-                rwlock_init(&newsk->sk_dst_lock);
+                spin_lock_init(&newsk->sk_dst_lock);
                 rwlock_init(&newsk->sk_callback_lock);
                 lockdep_set_class_and_name(&newsk->sk_callback_lock,
                                 af_callback_keys + newsk->sk_family,
@@ -1898,7 +1898,7 @@ void sock_init_data(struct socket *sock, struct sock *sk)
         } else
                 sk->sk_sleep    =       NULL;
 
-        rwlock_init(&sk->sk_dst_lock);
+        spin_lock_init(&sk->sk_dst_lock);
         rwlock_init(&sk->sk_callback_lock);
         lockdep_set_class_and_name(&sk->sk_callback_lock,
                         af_callback_keys + sk->sk_family,
diff --git a/net/dccp/timer.c b/net/dccp/timer.c
index bbfeb5eae46a..1a9aa05d4dc4 100644
--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -38,7 +38,7 @@ static int dccp_write_timeout(struct sock *sk)
 
         if (sk->sk_state == DCCP_REQUESTING || sk->sk_state == DCCP_PARTOPEN) {
                 if (icsk->icsk_retransmits != 0)
-                        dst_negative_advice(&sk->sk_dst_cache, sk);
+                        dst_negative_advice(sk);
                 retry_until = icsk->icsk_syn_retries ?
                             : sysctl_dccp_request_retries;
         } else {
@@ -63,7 +63,7 @@ static int dccp_write_timeout(struct sock *sk)
                            Golden words :-).
                    */
 
-                        dst_negative_advice(&sk->sk_dst_cache, sk);
+                        dst_negative_advice(sk);
                 }
 
                 retry_until = sysctl_dccp_retries2;
diff --git a/net/decnet/af_decnet.c b/net/decnet/af_decnet.c
index 2b494fac9468..55e3b6b0061a 100644
--- a/net/decnet/af_decnet.c
+++ b/net/decnet/af_decnet.c
@@ -446,7 +446,7 @@ static void dn_destruct(struct sock *sk)
         skb_queue_purge(&scp->other_xmit_queue);
         skb_queue_purge(&scp->other_receive_queue);
 
-        dst_release(xchg(&sk->sk_dst_cache, NULL));
+        dst_release(rcu_dereference_check(sk->sk_dst_cache, 1));
 }
 
 static int dn_memory_pressure;
@@ -1105,7 +1105,7 @@ static int dn_accept(struct socket *sock, struct socket *newsock, int flags)
         release_sock(sk);
 
         dst = skb_dst(skb);
-        dst_release(xchg(&newsk->sk_dst_cache, dst));
+        sk_dst_set(newsk, dst);
         skb_dst_set(skb, NULL);
 
         DN_SK(newsk)->state        = DN_CR;
@@ -1956,7 +1956,7 @@ static int dn_sendmsg(struct kiocb *iocb, struct socket *sock,
         }
 
         if ((flags & MSG_TRYHARD) && sk->sk_dst_cache)
-                dst_negative_advice(&sk->sk_dst_cache, sk);
+                dst_negative_advice(sk);
 
         mss = scp->segsize_rem;
         fctype = scp->services_rem & NSP_FC_MASK;
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index a0beb32beaa3..193dcd6ed64f 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -154,7 +154,7 @@ void inet_sock_destruct(struct sock *sk)
         WARN_ON(sk->sk_forward_alloc);
 
         kfree(inet->opt);
-        dst_release(sk->sk_dst_cache);
+        dst_release(rcu_dereference_check(sk->sk_dst_cache, 1));
         sk_refcnt_debug_dec(sk);
 }
 EXPORT_SYMBOL(inet_sock_destruct);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4000b10610b7..ae3ec15fb630 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3710,7 +3710,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
         }
 
         if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
-                dst_confirm(sk->sk_dst_cache);
+                dst_confirm(__sk_dst_get(sk));
 
         return 1;
 
@@ -5833,7 +5833,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                         if (tp->snd_una == tp->write_seq) {
                                 tcp_set_state(sk, TCP_FIN_WAIT2);
                                 sk->sk_shutdown |= SEND_SHUTDOWN;
-                                dst_confirm(sk->sk_dst_cache);
+                                dst_confirm(__sk_dst_get(sk));
 
                                 if (!sock_flag(sk, SOCK_DEAD))
                                         /* Wake up lingering close() */
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 8a0ab2977f1f..c732be00606b 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -172,14 +172,14 @@ static int tcp_write_timeout(struct sock *sk)
 
         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
                 if (icsk->icsk_retransmits)
-                        dst_negative_advice(&sk->sk_dst_cache, sk);
+                        dst_negative_advice(sk);
                 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
         } else {
                 if (retransmits_timed_out(sk, sysctl_tcp_retries1)) {
                         /* Black hole detection */
                         tcp_mtu_probing(icsk, sk);
 
-                        dst_negative_advice(&sk->sk_dst_cache, sk);
+                        dst_negative_advice(sk);
                 }
 
                 retry_until = sysctl_tcp_retries2;
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 33f60fca7aa7..1160400e9dbd 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -114,9 +114,9 @@ struct ipv6_txoptions *ipv6_update_options(struct sock *sk,
                 }
                 opt = xchg(&inet6_sk(sk)->opt, opt);
         } else {
-                write_lock(&sk->sk_dst_lock);
+                spin_lock(&sk->sk_dst_lock);
                 opt = xchg(&inet6_sk(sk)->opt, opt);
-                write_unlock(&sk->sk_dst_lock);
+                spin_unlock(&sk->sk_dst_lock);
         }
         sk_dst_reset(sk);
 
@@ -971,14 +971,13 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
         case IPV6_MTU:
         {
                 struct dst_entry *dst;
+
                 val = 0;
-                lock_sock(sk);
-                dst = sk_dst_get(sk);
-                if (dst) {
+                rcu_read_lock();
+                dst = __sk_dst_get(sk);
+                if (dst)
                         val = dst_mtu(dst);
-                        dst_release(dst);
-                }
-                release_sock(sk);
+                rcu_read_unlock();
                 if (!val)
                         return -ENOTCONN;
                 break;
@@ -1066,12 +1065,14 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
                 else
                         val = np->mcast_hops;
 
-                dst = sk_dst_get(sk);
-                if (dst) {
-                        if (val < 0)
+                if (val < 0) {
+                        rcu_read_lock();
+                        dst = __sk_dst_get(sk);
+                        if (dst)
                                 val = ip6_dst_hoplimit(dst);
-                        dst_release(dst);
+                        rcu_read_unlock();
                 }
+
                 if (val < 0)
                         val = sock_net(sk)->ipv6.devconf_all->hop_limit;
                 break;