can: c_can: Provide protection in the xmit path

The network core does not serialize the access to the hardware. The
xmit related code lets the following happen:

CPU0 	     	       CPU1
interrupt()
 do_poll()
   c_can_do_tx()
    Fiddle with HW and	xmit()
    internal data	  Fiddle with HW and
    	     		  internal data

due the complete lack of serialization.

Add proper locking.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

2 files changed, 9 insertions, 1 deletions

diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index 30a85aa81d45..1fe79ce50c5a 100644
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -549,6 +549,7 @@ static netdev_tx_t c_can_start_xmit(struct sk_buff *skb,
         if (can_dropped_invalid_skb(dev, skb))
                 return NETDEV_TX_OK;
 
+        spin_lock_bh(&priv->xmit_lock);
         msg_obj_no = get_tx_next_msg_obj(priv);
 
         /* prepare message object for transmission */
@@ -563,6 +564,7 @@ static netdev_tx_t c_can_start_xmit(struct sk_buff *skb,
         if (c_can_is_next_tx_obj_busy(priv, get_tx_next_msg_obj(priv)) ||
                         (priv->tx_next & C_CAN_NEXT_MSG_OBJ_MASK) == 0)
                 netif_stop_queue(dev);
+        spin_unlock_bh(&priv->xmit_lock);
 
         return NETDEV_TX_OK;
 }
@@ -787,7 +789,9 @@ static void c_can_do_tx(struct net_device *dev)
         struct c_can_priv *priv = netdev_priv(dev);
         struct net_device_stats *stats = &dev->stats;
 
-        for (/* nix */; (priv->tx_next - priv->tx_echo) > 0; priv->tx_echo++) {
+        spin_lock_bh(&priv->xmit_lock);
+
+        for (; (priv->tx_next - priv->tx_echo) > 0; priv->tx_echo++) {
                 msg_obj_no = get_tx_echo_msg_obj(priv);
                 val = c_can_read_reg32(priv, C_CAN_TXRQST1_REG);
                 if (!(val & (1 << (msg_obj_no - 1)))) {
@@ -809,6 +813,8 @@ static void c_can_do_tx(struct net_device *dev)
         if (((priv->tx_next & C_CAN_NEXT_MSG_OBJ_MASK) != 0) ||
                         ((priv->tx_echo & C_CAN_NEXT_MSG_OBJ_MASK) == 0))
                 netif_wake_queue(dev);
+
+        spin_unlock_bh(&priv->xmit_lock);
 }
 
 /*
@@ -1262,6 +1268,7 @@ struct net_device *alloc_c_can_dev(void)
                 return NULL;
 
         priv = netdev_priv(dev);
+        spin_lock_init(&priv->xmit_lock);
         netif_napi_add(dev, &priv->napi, c_can_poll, C_CAN_NAPI_WEIGHT);
 
         priv->dev = dev;
diff --git a/drivers/net/can/c_can/c_can.h b/drivers/net/can/c_can/c_can.h
index d2e1c21b143f..5097c802a61e 100644
--- a/drivers/net/can/c_can/c_can.h
+++ b/drivers/net/can/c_can/c_can.h
@@ -156,6 +156,7 @@ struct c_can_priv {
         struct napi_struct napi;
         struct net_device *dev;
         struct device *device;
+        spinlock_t xmit_lock;
         int tx_object;
         int current_status;
         int last_status;