wimax/i2400m: fix erroneous NETDEV_TX_BUSY use

A driver start_xmit() method cannot free skb and return NETDEV_TX_BUSY,
since caller is going to reuse freed skb.

In fact netif_tx_stop_queue() / netif_stop_queue() is needed before
returning NETDEV_TX_BUSY or you can trigger a ksoftirqd fatal loop.

In case of memory allocation error, only safe way is to drop the packet
and return NETDEV_TX_OK

Also increments tx_dropped counter

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 20 deletions

diff --git a/drivers/net/wimax/i2400m/netdev.c b/drivers/net/wimax/i2400m/netdev.c
index 64a110604ad..63e4b709efa 100644
--- a/drivers/net/wimax/i2400m/netdev.c
+++ b/drivers/net/wimax/i2400m/netdev.c
@@ -367,38 +367,28 @@ netdev_tx_t i2400m_hard_start_xmit(struct sk_buff *skb,
 {
         struct i2400m *i2400m = net_dev_to_i2400m(net_dev);
         struct device *dev = i2400m_dev(i2400m);
-        int result;
+        int result = -1;
 
         d_fnstart(3, dev, "(skb %p net_dev %p)\n", skb, net_dev);
-        if (skb_header_cloned(skb)) {
-                /*
-                 * Make tcpdump/wireshark happy -- if they are
-                 * running, the skb is cloned and we will overwrite
-                 * the mac fields in i2400m_tx_prep_header. Expand
-                 * seems to fix this...
-                 */
-                result = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-                if (result) {
-                        result = NETDEV_TX_BUSY;
-                        goto error_expand;
-                }
-        }
+
+        if (skb_header_cloned(skb) && 
+            pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+                goto drop;
 
         if (i2400m->state == I2400M_SS_IDLE)
                 result = i2400m_net_wake_tx(i2400m, net_dev, skb);
         else
                 result = i2400m_net_tx(i2400m, net_dev, skb);
-        if (result <  0)
+        if (result <  0) {
+drop:
                 net_dev->stats.tx_dropped++;
-        else {
+        } else {
                 net_dev->stats.tx_packets++;
                 net_dev->stats.tx_bytes += skb->len;
         }
-        result = NETDEV_TX_OK;
-error_expand:
-        kfree_skb(skb);
+        dev_kfree_skb(skb);
         d_fnend(3, dev, "(skb %p net_dev %p) = %d\n", skb, net_dev, result);
-        return result;
+        return NETDEV_TX_OK;
 }