[NET]: Fix sk->sk_filter field access

Function sk_filter() is called from tcp_v{4,6}_rcv() functions with arg
needlock = 0, while socket is not locked at that moment. In order to avoid
this and similar issues in the future, use rcu for sk->sk_filter field read
protection.

Signed-off-by: Dmitry Mishin <dim@openvz.org>
Signed-off-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: Kirill Korotaev <dev@openvz.org>

2 files changed, 13 insertions, 17 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 5b4486a60cf6..6732782a5a40 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -422,10 +422,10 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
         if (!err) {
                 struct sk_filter *old_fp;
 
-                spin_lock_bh(&sk->sk_lock.slock);
-                old_fp = sk->sk_filter;
-                sk->sk_filter = fp;
-                spin_unlock_bh(&sk->sk_lock.slock);
+                rcu_read_lock_bh();
+                old_fp = rcu_dereference(sk->sk_filter);
+                rcu_assign_pointer(sk->sk_filter, fp);
+                rcu_read_unlock_bh();
                 fp = old_fp;
         }
 
diff --git a/net/core/sock.c b/net/core/sock.c
index cfaf09039b02..b77e155cbe6c 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -247,11 +247,7 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
                 goto out;
         }
 
-        /* It would be deadlock, if sock_queue_rcv_skb is used
-           with socket lock! We assume that users of this
-           function are lock free.
-        */
-        err = sk_filter(sk, skb, 1);
+        err = sk_filter(sk, skb);
         if (err)
                 goto out;
 
@@ -278,7 +274,7 @@ int sk_receive_skb(struct sock *sk, struct sk_buff *skb)
 {
         int rc = NET_RX_SUCCESS;
 
-        if (sk_filter(sk, skb, 0))
+        if (sk_filter(sk, skb))
                 goto discard_and_relse;
 
         skb->dev = NULL;
@@ -606,15 +602,15 @@ set_rcvbuf:
                         break;
 
                 case SO_DETACH_FILTER:
-                        spin_lock_bh(&sk->sk_lock.slock);
-                        filter = sk->sk_filter;
+                        rcu_read_lock_bh();
+                        filter = rcu_dereference(sk->sk_filter);
                         if (filter) {
-                                sk->sk_filter = NULL;
-                                spin_unlock_bh(&sk->sk_lock.slock);
+                                rcu_assign_pointer(sk->sk_filter, NULL);
                                 sk_filter_release(sk, filter);
+                                rcu_read_unlock_bh();
                                 break;
                         }
-                        spin_unlock_bh(&sk->sk_lock.slock);
+                        rcu_read_unlock_bh();
                         ret = -ENONET;
                         break;
 
@@ -884,10 +880,10 @@ void sk_free(struct sock *sk)
         if (sk->sk_destruct)
                 sk->sk_destruct(sk);
 
-        filter = sk->sk_filter;
+        filter = rcu_dereference(sk->sk_filter);
         if (filter) {
                 sk_filter_release(sk, filter);
-                sk->sk_filter = NULL;
+                rcu_assign_pointer(sk->sk_filter, NULL);
         }
 
         sock_disable_timestamp(sk);