netlink: fix races after skb queueing

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>

1 files changed, 13 insertions, 11 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 32bb75324e76..faa48f70b7c9 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -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);