net: arc_emac: fix arc_emac_rx() error paths

arc_emac_rx() has some issues found by code review.

In case netdev_alloc_skb_ip_align() or dma_map_single() failure
rx fifo entry will not be returned to EMAC.

In case dma_map_single() failure previously allocated skb became
lost to driver. At the same time address of newly allocated skb
will not be provided to EMAC.

Signed-off-by: Alexander Kochetkov <al.kochet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 22 deletions

diff --git a/drivers/net/ethernet/arc/emac_main.c b/drivers/net/ethernet/arc/emac_main.c
index 3241af1ce718..5b422be56165 100644
--- a/drivers/net/ethernet/arc/emac_main.c
+++ b/drivers/net/ethernet/arc/emac_main.c
@@ -210,39 +210,48 @@ static int arc_emac_rx(struct net_device *ndev, int budget)
                         continue;
                 }
 
-                pktlen = info & LEN_MASK;
-                stats->rx_packets++;
-                stats->rx_bytes += pktlen;
-                skb = rx_buff->skb;
-                skb_put(skb, pktlen);
-                skb->dev = ndev;
-                skb->protocol = eth_type_trans(skb, ndev);
-
-                dma_unmap_single(&ndev->dev, dma_unmap_addr(rx_buff, addr),
-                                 dma_unmap_len(rx_buff, len), DMA_FROM_DEVICE);
-
-                /* Prepare the BD for next cycle */
-                rx_buff->skb = netdev_alloc_skb_ip_align(ndev,
-                                                         EMAC_BUFFER_SIZE);
-                if (unlikely(!rx_buff->skb)) {
+                /* Prepare the BD for next cycle. netif_receive_skb()
+                 * only if new skb was allocated and mapped to avoid holes
+                 * in the RX fifo.
+                 */
+                skb = netdev_alloc_skb_ip_align(ndev, EMAC_BUFFER_SIZE);
+                if (unlikely(!skb)) {
+                        if (net_ratelimit())
+                                netdev_err(ndev, "cannot allocate skb\n");
+                        /* Return ownership to EMAC */
+                        rxbd->info = cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
                         stats->rx_errors++;
-                        /* Because receive_skb is below, increment rx_dropped */
                         stats->rx_dropped++;
                         continue;
                 }
 
-                /* receive_skb only if new skb was allocated to avoid holes */
-                netif_receive_skb(skb);
-
-                addr = dma_map_single(&ndev->dev, (void *)rx_buff->skb->data,
+                addr = dma_map_single(&ndev->dev, (void *)skb->data,
                                       EMAC_BUFFER_SIZE, DMA_FROM_DEVICE);
                 if (dma_mapping_error(&ndev->dev, addr)) {
                         if (net_ratelimit())
-                                netdev_err(ndev, "cannot dma map\n");
-                        dev_kfree_skb(rx_buff->skb);
+                                netdev_err(ndev, "cannot map dma buffer\n");
+                        dev_kfree_skb(skb);
+                        /* Return ownership to EMAC */
+                        rxbd->info = cpu_to_le32(FOR_EMAC | EMAC_BUFFER_SIZE);
                         stats->rx_errors++;
+                        stats->rx_dropped++;
                         continue;
                 }
+
+                /* unmap previosly mapped skb */
+                dma_unmap_single(&ndev->dev, dma_unmap_addr(rx_buff, addr),
+                                 dma_unmap_len(rx_buff, len), DMA_FROM_DEVICE);
+
+                pktlen = info & LEN_MASK;
+                stats->rx_packets++;
+                stats->rx_bytes += pktlen;
+                skb_put(rx_buff->skb, pktlen);
+                rx_buff->skb->dev = ndev;
+                rx_buff->skb->protocol = eth_type_trans(rx_buff->skb, ndev);
+
+                netif_receive_skb(rx_buff->skb);
+
+                rx_buff->skb = skb;
                 dma_unmap_addr_set(rx_buff, addr, addr);
                 dma_unmap_len_set(rx_buff, len, EMAC_BUFFER_SIZE);