net: kernel panic in dev_hard_start_xmit: remove faulty software TX time stamping

The current implementation of the TX software time stamping fallback is
faulty because it accesses the skb after ndo_start_xmit() returns
successfully. This patch removes the fallback, which fixes kernel panics
seen during stress tests. Hardware time stamping is not affected by this
removal.

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index 5493394..88dc082 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1672,16 +1672,6 @@ static int dev_gso_segment(struct sk_buff *skb)
        return 0;
 }
 
-static void tstamp_tx(struct sk_buff *skb)
-{
-       union skb_shared_tx *shtx =
-               skb_tx(skb);
-       if (unlikely(shtx->software &&
-                       !shtx->in_progress)) {
-               skb_tstamp_tx(skb, NULL);
-       }
-}
-
 int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
                        struct netdev_queue *txq)
 {
@@ -1715,8 +1705,6 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
                 * the skb destructor before the call and restoring it
                 * afterwards, then doing the skb_orphan() ourselves?
                 */
-               if (likely(!rc))
-                       tstamp_tx(skb);
                return rc;
        }
 
@@ -1732,7 +1720,6 @@ gso:
                        skb->next = nskb;
                        return rc;
                }
-               tstamp_tx(skb);
                if (unlikely(netif_tx_queue_stopped(txq) && skb->next))
                        return NETDEV_TX_BUSY;
        } while (skb->next);