[PATCH net 9/9] net/mlx4_en: Fix panic on xmit while port is down

[Tariq Toukan]

From: Moshe Shemesh <mo...@mellanox.com>

When port is down, tx drop counter update is not needed.
Updating the counter in this case can cause a kernel
panic as when the port is down, ring can be NULL.

Fixes: 63a664b7e92b ("net/mlx4_en: fix tx_dropped bug")
Signed-off-by: Moshe Shemesh <mo...@mellanox.com>
Signed-off-by: Tariq Toukan <tar...@mellanox.com>
---
 drivers/net/ethernet/mellanox/mlx4/en_tx.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c 
b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 9df87ca0515a..e2509bba3e7c 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -818,7 +818,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct 
net_device *dev)
        real_size = get_real_size(skb, shinfo, dev, &lso_header_size,
                                  &inline_ok, &fragptr);
        if (unlikely(!real_size))
-               goto tx_drop;
+               goto tx_drop_count;
 
        /* Align descriptor to TXBB size */
        desc_size = ALIGN(real_size, TXBB_SIZE);
@@ -826,7 +826,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct 
net_device *dev)
        if (unlikely(nr_txbb > MAX_DESC_TXBBS)) {
                if (netif_msg_tx_err(priv))
                        en_warn(priv, "Oversized header or SG list\n");
-               goto tx_drop;
+               goto tx_drop_count;
        }
 
        bf_ok = ring->bf_enabled;
@@ -1071,9 +1071,10 @@ tx_drop_unmap:
                               PCI_DMA_TODEVICE);
        }
 
+tx_drop_count:
+       ring->tx_dropped++;
 tx_drop:
        dev_kfree_skb_any(skb);
-       ring->tx_dropped++;
        return NETDEV_TX_OK;
 }
 
@@ -1106,7 +1107,7 @@ netdev_tx_t mlx4_en_xmit_frame(struct mlx4_en_rx_alloc 
*frame,
                goto tx_drop;
 
        if (mlx4_en_is_tx_ring_full(ring))
-               goto tx_drop;
+               goto tx_drop_count;
 
        /* fetch ring->cons far ahead before needing it to avoid stall */
        ring_cons = READ_ONCE(ring->cons);
@@ -1176,7 +1177,8 @@ netdev_tx_t mlx4_en_xmit_frame(struct mlx4_en_rx_alloc 
*frame,
 
        return NETDEV_TX_OK;
 
-tx_drop:
+tx_drop_count:
        ring->tx_dropped++;
+tx_drop:
        return NETDEV_TX_BUSY;
 }
-- 
1.8.3.1