can: c_can: Do not access skb after net_receive_skb()

There is no guarantee that the skb is in the same state after calling
net_receive_skb(). It might be freed or reused. Not really harmful as
its a read access, except you turn on the proper debugging options
which catch a use after free.

The whole can subsystem is full of this. Copy and paste ....

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index 8c725f4..6038761 100644 (file)
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -429,10 +429,10 @@ static int c_can_read_msg_object(struct net_device *dev, int iface, int ctrl)
                }
        }
 
-       netif_receive_skb(skb);
-
        stats->rx_packets++;
        stats->rx_bytes += frame->can_dlc;
+
+       netif_receive_skb(skb);
        return 0;
 }
 
@@ -960,9 +960,9 @@ static int c_can_handle_state_change(struct net_device *dev,
                break;
        }
 
-       netif_receive_skb(skb);
        stats->rx_packets++;
        stats->rx_bytes += cf->can_dlc;
+       netif_receive_skb(skb);
 
        return 1;
 }
@@ -1033,10 +1033,9 @@ static int c_can_handle_bus_err(struct net_device *dev,
        /* set a `lec` value so that we can check for updates later */
        priv->write_reg(priv, C_CAN_STS_REG, LEC_UNUSED);
 
-       netif_receive_skb(skb);
        stats->rx_packets++;
        stats->rx_bytes += cf->can_dlc;
-
+       netif_receive_skb(skb);
        return 1;
 }