netlink: fix races after skb queueing
Eric Dumazet [Thu, 5 Apr 2012 22:17:46 +0000 (22:17 +0000)]
As soon as an skb is queued into socket receive_queue, another thread
can consume it, so we are not allowed to reference skb anymore, or risk
use after free.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/af_netlink.c

index 32bb753..faa48f7 100644 (file)
@@ -829,12 +829,19 @@ int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
        return 0;
 }
 
-int netlink_sendskb(struct sock *sk, struct sk_buff *skb)
+static int __netlink_sendskb(struct sock *sk, struct sk_buff *skb)
 {
        int len = skb->len;
 
        skb_queue_tail(&sk->sk_receive_queue, skb);
        sk->sk_data_ready(sk, len);
+       return len;
+}
+
+int netlink_sendskb(struct sock *sk, struct sk_buff *skb)
+{
+       int len = __netlink_sendskb(sk, skb);
+
        sock_put(sk);
        return len;
 }
@@ -957,8 +964,7 @@ static int netlink_broadcast_deliver(struct sock *sk, struct sk_buff *skb)
        if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
            !test_bit(0, &nlk->state)) {
                skb_set_owner_r(skb, sk);
-               skb_queue_tail(&sk->sk_receive_queue, skb);
-               sk->sk_data_ready(sk, skb->len);
+               __netlink_sendskb(sk, skb);
                return atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1);
        }
        return -1;
@@ -1698,10 +1704,8 @@ static int netlink_dump(struct sock *sk)
 
                if (sk_filter(sk, skb))
                        kfree_skb(skb);
-               else {
-                       skb_queue_tail(&sk->sk_receive_queue, skb);
-                       sk->sk_data_ready(sk, skb->len);
-               }
+               else
+                       __netlink_sendskb(sk, skb);
                return 0;
        }
 
@@ -1715,10 +1719,8 @@ static int netlink_dump(struct sock *sk)
 
        if (sk_filter(sk, skb))
                kfree_skb(skb);
-       else {
-               skb_queue_tail(&sk->sk_receive_queue, skb);
-               sk->sk_data_ready(sk, skb->len);
-       }
+       else
+               __netlink_sendskb(sk, skb);
 
        if (cb->done)
                cb->done(cb);