net: preserve IP control block during GSO segmentation

[mirror_ubuntu-bionic-kernel.git] / net / core / dev.c

diff --git a/net/core/dev.c b/net/core/dev.c
index 0ca95d5d7af0a397654cc85f44f9e474b7cc3061..cc9e3652cf93a6306e6f614f966e0fe7cf17a10e 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2695,6 +2695,8 @@ static inline bool skb_needs_check(struct sk_buff *skb, bool tx_path)
  *
  *     It may return NULL if the skb requires no segmentation.  This is
  *     only possible when GSO is used for verifying header integrity.
+ *
+ *     Segmentation preserves SKB_SGO_CB_OFFSET bytes of previous skb cb.
  */
 struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
                                  netdev_features_t features, bool tx_path)
@@ -2709,6 +2711,9 @@ struct sk_buff *__skb_gso_segment(struct sk_buff *skb,
                        return ERR_PTR(err);
        }
 
+       BUILD_BUG_ON(SKB_SGO_CB_OFFSET +
+                    sizeof(*SKB_GSO_CB(skb)) > sizeof(skb->cb));
+
        SKB_GSO_CB(skb)->mac_offset = skb_headroom(skb);
        SKB_GSO_CB(skb)->encap_level = 0;