can: cc770: Fix use after free in cc770_tx_interrupt()

BugLink: http://bugs.launchpad.net/bugs/1764973

commit 9ffd7503 upstream.

This fixes use after free introduced by the last cc770 patch.
Signed-off-by: Andri Yngvason <andri.yngvason@marel.com>
Fixes: 74620123 ("can: cc770: Fix queue stall & dropped RTR reply")
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/net/can/cc770/cc770.c

@@ -706,13 +706,12 @@ static void cc770_tx_interrupt(struct net_device *dev, unsigned int o)
 		return;
 	}
 
-	can_put_echo_skb(priv->tx_skb, dev, 0);
-	can_get_echo_skb(dev, 0);
-
 	cf = (struct can_frame *)priv->tx_skb->data;
 	stats->tx_bytes += cf->can_dlc;
 	stats->tx_packets++;
 
+	can_put_echo_skb(priv->tx_skb, dev, 0);
+	can_get_echo_skb(dev, 0);
 	priv->tx_skb = NULL;
 
 	netif_wake_queue(dev);