[PATCH 4.4 15/86] can: dev: __can_get_echo_skb(): print error message, if trying to echo non existing skb

Greg Kroah-Hartman
2018-11-29T14:17:14Z

From: Marc Kleine-Budde <mkl@pengutronix.de>

commit 7da11ba5c5066dadc2e96835a6233d56d7b7764a upstream.

Prior to echoing a successfully transmitted CAN frame (by calling
can_get_echo_skb()), CAN drivers have to put the CAN frame (by calling
can_put_echo_skb() in the transmit function). These put and get function
take an index as parameter, which is used to identify the CAN frame.

A driver calling can_get_echo_skb() with a index not pointing to a skb
is a BUG, so add an appropriate error message.

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>

---
drivers/net/can/dev.c | 27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)

--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -426,6 +426,8 @@ EXPORT_SYMBOL_GPL(can_put_echo_skb);
struct sk_buff *__can_get_echo_skb(struct net_device *dev, unsigned int idx, u8 *len_ptr)
{
struct can_priv *priv = netdev_priv(dev);
+ struct sk_buff *skb = priv->echo_skb[idx];
+ struct canfd_frame *cf;

if (idx >= priv->echo_skb_max) {
netdev_err(dev, "%s: BUG! Trying to access can_priv::echo_skb out of bounds (%u/max %u)\n",
@@ -433,21 +435,20 @@ struct sk_buff *__can_get_echo_skb(struc
return NULL;
}

- if (priv->echo_skb[idx]) {
- /* Using "struct canfd_frame::len" for the frame
- * length is supported on both CAN and CANFD frames.
- */
- struct sk_buff *skb = priv->echo_skb[idx];
- struct canfd_frame *cf = (struct canfd_frame *)skb->data;
- u8 len = cf->len;
-
- *len_ptr = len;
- priv->echo_skb[idx] = NULL;
-
- return skb;
+ if (!skb) {
+ netdev_err(dev, "%s: BUG! Trying to echo non existing skb: can_priv::echo_skb[%u]\n",
+ __func__, idx);
+ return NULL;
}

- return NULL;
+ /* Using "struct canfd_frame::len" for the frame
+ * length is supported on both CAN and CANFD frames.
+ */
+ cf = (struct canfd_frame *)skb->data;
+ *len_ptr = cf->len;
+ priv->echo_skb[idx] = NULL;
+
+ return skb;
}

/*