On Sun, 2015-12-06 at 13:03 -0800, Eric Dumazet wrote:
> But then when later we promote a skb->dst to a refctounted one
> (skb_dst_force(), we might make sure we abort the operation if __refcnt
> == 0 ( and DST_NOCACHE is in dst->flags)
>
Minimum patch would be :
diff --git a/include/net/dst.h b/include/net/dst.h
index 1279f9b09791..b9a3239f4296 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -322,6 +322,24 @@ static inline void skb_dst_force(struct sk_buff *skb)
}
}
+/**
+ * skb_dst_force_safe - makes sure skb dst is refcounted
+ * @skb: buffer
+ *
+ * If dst is not yet refcounted and not destroyed, grab a ref on it.
+ */
+static inline void skb_dst_force_safe(struct sk_buff *skb)
+{
+ if (skb_dst_is_noref(skb)) {
+ struct dst_entry *dst = skb_dst(skb);
+
+ if (!atomic_inc_not_zero(&dst->__refcnt))
+ dst = NULL;
+
+ skb->_skb_refdst = (unsigned long)dst;
+ }
+}
+
/**
* __skb_tunnel_rx - prepare skb for rx reinsert
diff --git a/include/net/sock.h b/include/net/sock.h
index b1d475b5db68..6367d1112c3d 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -816,7 +816,7 @@ void sk_stream_write_space(struct sock *sk);
static inline void __sk_add_backlog(struct sock *sk, struct sk_buff *skb)
{
/* dont let skb dst not refcounted, we are going to leave rcu lock */
- skb_dst_force(skb);
+ skb_dst_force_safe(skb);
if (!sk->sk_backlog.tail)
sk->sk_backlog.head = skb;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index db003438aaf5..a72688a288f5 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1493,7 +1493,7 @@ bool tcp_prequeue(struct sock *sk, struct sk_buff *skb)
if (likely(sk->sk_rx_dst))
skb_dst_drop(skb);
else
- skb_dst_force(skb);
+ skb_dst_force_safe(skb);
__skb_queue_tail(&tp->ucopy.prequeue, skb);
tp->ucopy.memory += skb->truesize;
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
