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can: dev: __can_get_echo_skb(): fix bogous check for non-existing skb by removing it

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This patch revert commit 7da11ba5c5
("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: 7da11ba5c5 ("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>
This commit is contained in:
Manfred Schlaegl 2018-12-19 19:39:58 +01:00 committed by Marc Kleine-Budde
parent 49a57857ae
commit 7b12c8189a
1 changed files with 13 additions and 14 deletions
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27
drivers/net/can/dev.c
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@ -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;
*len_ptr = len;
priv->echo_skb[idx] = NULL;
return skb;
}
/* 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;
return NULL;
}
/*