can: dev: can_restart: fix use after free bug

After calling netif_rx_ni(skb), dereferencing skb is unsafe.
Especially, the can_frame cf which aliases skb memory is accessed
after the netif_rx_ni() in:
      stats->rx_bytes += cf->len;

Reordering the lines solves the issue.

Fixes: 39549eef3587 ("can: CAN Network device driver and Netlink interface")
Link: https://lore.kernel.org/r/20210120114137.200019-2-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 3486704..8b1ae02 100644 (file)
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -592,11 +592,11 @@ static void can_restart(struct net_device *dev)
 
        cf->can_id |= CAN_ERR_RESTARTED;
 
-       netif_rx_ni(skb);
-
        stats->rx_packets++;
        stats->rx_bytes += cf->len;
 
+       netif_rx_ni(skb);
+
 restart:
        netdev_dbg(dev, "restarted\n");
        priv->can_stats.restarts++;