net: moxa: fix TX overrun memory leak

moxart_mac_start_xmit() doesn't care where tx_tail is, tx_head can
catch and pass tx_tail, which is bad because moxart_tx_finished()
isn't guaranteed to catch up on freeing resources from tx_tail.

Add a check in moxart_mac_start_xmit() stopping the queue at the
end of the circular buffer. Also add a check in moxart_tx_finished()
waking the queue if the buffer has TX_WAKE_THRESHOLD or more
free descriptors.

While we're at it, move spin_lock_irq() to happen before our
descriptor pointer is assigned in moxart_mac_start_xmit().

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=99451

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 06c9f41..6ad44be 100644 (file)
--- a/drivers/net/ethernet/moxa/moxart_ether.c
+++ b/drivers/net/ethernet/moxa/moxart_ether.c
@@ -25,6 +25,7 @@
 #include <linux/of_irq.h>
 #include <linux/crc32.h>
 #include <linux/crc32c.h>
+#include <linux/circ_buf.h>
 
 #include "moxart_ether.h"
 
@@ -278,6 +279,13 @@ rx_next:
        return rx;
 }
 
+static int moxart_tx_queue_space(struct net_device *ndev)
+{
+       struct moxart_mac_priv_t *priv = netdev_priv(ndev);
+
+       return CIRC_SPACE(priv->tx_head, priv->tx_tail, TX_DESC_NUM);
+}
+
 static void moxart_tx_finished(struct net_device *ndev)
 {
        struct moxart_mac_priv_t *priv = netdev_priv(ndev);
@@ -297,6 +305,9 @@ static void moxart_tx_finished(struct net_device *ndev)
                tx_tail = TX_NEXT(tx_tail);
        }
        priv->tx_tail = tx_tail;
+       if (netif_queue_stopped(ndev) &&
+           moxart_tx_queue_space(ndev) >= TX_WAKE_THRESHOLD)
+               netif_wake_queue(ndev);
 }
 
 static irqreturn_t moxart_mac_interrupt(int irq, void *dev_id)
@@ -324,13 +335,18 @@ static int moxart_mac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
        struct moxart_mac_priv_t *priv = netdev_priv(ndev);
        void *desc;
        unsigned int len;
-       unsigned int tx_head = priv->tx_head;
+       unsigned int tx_head;
        u32 txdes1;
        int ret = NETDEV_TX_BUSY;
 
+       spin_lock_irq(&priv->txlock);
+
+       tx_head = priv->tx_head;
        desc = priv->tx_desc_base + (TX_REG_DESC_SIZE * tx_head);
 
-       spin_lock_irq(&priv->txlock);
+       if (moxart_tx_queue_space(ndev) == 1)
+               netif_stop_queue(ndev);
+
        if (moxart_desc_read(desc + TX_REG_OFFSET_DESC0) & TX_DESC0_DMA_OWN) {
                net_dbg_ratelimited("no TX space for packet\n");
                priv->stats.tx_dropped++;

diff --git a/drivers/net/ethernet/moxa/moxart_ether.h b/drivers/net/ethernet/moxa/moxart_ether.h
index 93a9563..afc32ec 100644 (file)
--- a/drivers/net/ethernet/moxa/moxart_ether.h
+++ b/drivers/net/ethernet/moxa/moxart_ether.h
@@ -59,6 +59,7 @@
 #define TX_NEXT(N)             (((N) + 1) & (TX_DESC_NUM_MASK))
 #define TX_BUF_SIZE            1600
 #define TX_BUF_SIZE_MAX                (TX_DESC1_BUF_SIZE_MASK+1)
+#define TX_WAKE_THRESHOLD      16
 
 #define RX_DESC_NUM            64
 #define RX_DESC_NUM_MASK       (RX_DESC_NUM-1)