net: moxa: replace build_skb() with netdev_alloc_skb_ip_align() / memcpy()

build_skb() is used to make skbs out of existing RX ring memory
which is bad because the RX ring is allocated only once, on probe.
Memory corruption occur because said memory is reclaimed, i.e.
__kfree_skb() (and eventually put_page()).

Replace build_skb() with netdev_alloc_skb_ip_align() and use memcpy().

Remove SKB_DATA_ALIGN() from RX buffer size while we're at it.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=69041

Signed-off-by: Jonas Jensen <jonas.jensen@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/moxa/moxart_ether.c b/drivers/net/ethernet/moxa/moxart_ether.c
index eed70d9f0d9db3656c9de37d432b5c31cc9a8962..d66058d5c4292c54f43060f5203e2097bf8706e5 100644 (file)
--- a/drivers/net/ethernet/moxa/moxart_ether.c
+++ b/drivers/net/ethernet/moxa/moxart_ether.c
@@ -226,13 +226,15 @@ static int moxart_rx_poll(struct napi_struct *napi, int budget)
                if (len > RX_BUF_SIZE)
                        len = RX_BUF_SIZE;
 
-               skb = build_skb(priv->rx_buf[rx_head], priv->rx_buf_size);
+               skb = netdev_alloc_skb_ip_align(ndev, len);
+
                if (unlikely(!skb)) {
-                       net_dbg_ratelimited("build_skb failed\n");
+                       net_dbg_ratelimited("netdev_alloc_skb_ip_align failed\n");
                        priv->stats.rx_dropped++;
                        priv->stats.rx_errors++;
                }
 
+               memcpy(skb->data, priv->rx_buf[rx_head], len);
                skb_put(skb, len);
                skb->protocol = eth_type_trans(skb, ndev);
                napi_gro_receive(&priv->napi, skb);
@@ -464,8 +466,7 @@ static int moxart_mac_probe(struct platform_device *pdev)
        spin_lock_init(&priv->txlock);
 
        priv->tx_buf_size = TX_BUF_SIZE;
-       priv->rx_buf_size = RX_BUF_SIZE +
-                           SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+       priv->rx_buf_size = RX_BUF_SIZE;
 
        priv->tx_desc_base = dma_alloc_coherent(NULL, TX_REG_DESC_SIZE *
                                                TX_DESC_NUM, &priv->tx_base,