From: Manfred Schlaegl manfred.schlaegl@ginzinger.com

This patch revert commit 7da11ba5c506 ("can: dev: __can_get_echo_skb(): print error message, if trying to echo non existing skb")

After introduction of this change we encountered following new error message on various i.MX plattforms (flexcan):

| flexcan 53fc8000.can can0: __can_get_echo_skb: BUG! Trying to echo non | existing skb: can_priv::echo_skb[0]

The introduction of the message was a mistake because priv->echo_skb[idx] = NULL is a perfectly valid in following case: If CAN_RAW_LOOPBACK is disabled (setsockopt) in applications, the pkt_type of the tx skb's given to can_put_echo_skb is set to PACKET_LOOPBACK. In this case can_put_echo_skb will not set priv->echo_skb[idx]. It is therefore kept NULL.

As additional argument for revert: The order of check and usage of idx was changed. idx is used to access an array element before checking it's boundaries.

Signed-off-by: Manfred Schlaegl manfred.schlaegl@ginzinger.com Fixes: 7da11ba5c506 ("can: dev: __can_get_echo_skb(): print error message, if trying to echo non existing skb") Cc: linux-stable stable@vger.kernel.org Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de --- drivers/net/can/dev.c | 27 +++++++++++++-------------- 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c index 3b3f88ffab53..c05e4d50d43d 100644 --- a/drivers/net/can/dev.c +++ b/drivers/net/can/dev.c @@ -480,8 +480,6 @@ 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", @@ -489,20 +487,21 @@ struct sk_buff *__can_get_echo_skb(struct net_device *dev, unsigned int idx, u8 return NULL; }

- if (!skb) { - netdev_err(dev, "%s: BUG! Trying to echo non existing skb: can_priv::echo_skb[%u]\n", - __func__, idx); - 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;

- /* 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; + *len_ptr = len; + priv->echo_skb[idx] = NULL;

- return skb; + return skb; + } + + return NULL; }

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