net: broadcom: bcm4908_enet: update TX stats after actual transmission

Queueing packets doesn't guarantee their transmission. Update TX stats
after hardware confirms consuming submitted data.

This also fixes a possible race and NULL dereference.
bcm4908_enet_start_xmit() could try to access skb after freeing it in
the bcm4908_enet_poll_tx().

Reported-by: Florian Fainelli <f.fainelli@gmail.com>
Fixes: 4feffeadbcb2e ("net: broadcom: bcm4908enet: add BCM4908 controller driver")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20221027112430.8696-1-zajec5@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/broadcom/bcm4908_enet.c b/drivers/net/ethernet/broadcom/bcm4908_enet.c
index 93ccf54..a737b19 100644 (file)
--- a/drivers/net/ethernet/broadcom/bcm4908_enet.c
+++ b/drivers/net/ethernet/broadcom/bcm4908_enet.c
@@ -561,8 +561,6 @@ static netdev_tx_t bcm4908_enet_start_xmit(struct sk_buff *skb, struct net_devic
 
        if (++ring->write_idx == ring->length - 1)
                ring->write_idx = 0;
-       enet->netdev->stats.tx_bytes += skb->len;
-       enet->netdev->stats.tx_packets++;
 
        return NETDEV_TX_OK;
 }
@@ -635,6 +633,7 @@ static int bcm4908_enet_poll_tx(struct napi_struct *napi, int weight)
        struct bcm4908_enet_dma_ring_bd *buf_desc;
        struct bcm4908_enet_dma_ring_slot *slot;
        struct device *dev = enet->dev;
+       unsigned int bytes = 0;
        int handled = 0;
 
        while (handled < weight && tx_ring->read_idx != tx_ring->write_idx) {
@@ -645,12 +644,17 @@ static int bcm4908_enet_poll_tx(struct napi_struct *napi, int weight)
 
                dma_unmap_single(dev, slot->dma_addr, slot->len, DMA_TO_DEVICE);
                dev_kfree_skb(slot->skb);
-               if (++tx_ring->read_idx == tx_ring->length)
-                       tx_ring->read_idx = 0;
 
                handled++;
+               bytes += slot->len;
+
+               if (++tx_ring->read_idx == tx_ring->length)
+                       tx_ring->read_idx = 0;
        }
 
+       enet->netdev->stats.tx_packets += handled;
+       enet->netdev->stats.tx_bytes += bytes;
+
        if (handled < weight) {
                napi_complete_done(napi, handled);
                bcm4908_enet_dma_ring_intrs_on(enet, tx_ring);