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    Subject[PATCH 3.18 12/83] can: dev: __can_get_echo_skb(): print error message, if trying to echo non existing skb
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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
    @@ -346,6 +346,8 @@ 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",
    @@ -353,21 +355,20 @@ 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;
    }

    /*

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