@@ -312,6 +312,39 @@ static inline void skb_dst_force(struct sk_buff *skb)
}
}
+/**
+ * dst_hold_safe - Take a reference on a dst if possible
+ * @dst: pointer to dst entry
+ *
+ * This helper returns false if it could not safely
+ * take a reference on a dst.
+ */
+static inline bool dst_hold_safe(struct dst_entry *dst)
+{
+ if (dst->flags & DST_NOCACHE)
+ return atomic_inc_not_zero(&dst->__refcnt);
+ dst_hold(dst);
+ return true;
+}
+
+/**
+ * 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 (!dst_hold_safe(dst))
+ dst = NULL;
+
+ skb->_skb_refdst = (unsigned long)dst;
+ }
+}
+
/**
* __skb_tunnel_rx - prepare skb for rx reinsert
@@ -798,7 +798,7 @@ 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;
@@ -1555,7 +1555,7 @@ 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;
@@ -1760,8 +1760,7 @@ void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
- if (dst) {
- dst_hold(dst);
+ if (dst && dst_hold_safe(dst)) {
sk->sk_rx_dst = dst;
inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
}
@@ -93,10 +93,9 @@ static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
- if (dst) {
+ if (dst && dst_hold_safe(dst)) {
const struct rt6_info *rt = (const struct rt6_info *)dst;
- dst_hold(dst);
sk->sk_rx_dst = dst;
inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
if (rt->rt6i_node)