[net,v2,1/3] net: bcmgenet: fix off-by-one in incrementing read pointer

Commit b629be5c8399d7c423b92135eb43a86c924d1cbc ("net: bcmgenet: check
harder for out of memory conditions") moved the increment of the local
read pointer *before* reading from the hardware descriptor using
dmadesc_get_length_status(), which creates an off-by-one situation.

Fix this by moving again the read_ptr increment after we have read the
hardware descriptor to get both the control block and the read pointer
back in sync.

Fixes: b629be5c8399 ("net: bcmgenet: check harder for out of memory conditions")
Signed-off-by: Jaedon Shin <jaedon.shin@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
Changes in v2:
- moved the rxpktprocessed and rx_read_ptr increment after refiling the control
  block

 drivers/net/ethernet/broadcom/genet/bcmgenet.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

Looks good to me.

On Fri, Oct 10, 2014 at 10:51 AM, Florian Fainelli <f.fainelli@gmail.com> wrote:
> Commit b629be5c8399d7c423b92135eb43a86c924d1cbc ("net: bcmgenet: check
> harder for out of memory conditions") moved the increment of the local
> read pointer *before* reading from the hardware descriptor using
> dmadesc_get_length_status(), which creates an off-by-one situation.
>
> Fix this by moving again the read_ptr increment after we have read the
> hardware descriptor to get both the control block and the read pointer
> back in sync.
>
> Fixes: b629be5c8399 ("net: bcmgenet: check harder for out of memory conditions")
> Signed-off-by: Jaedon Shin <jaedon.shin@gmail.com>
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

Acked-by: Petri Gynther <pgynther@google.com>

> ---
> Changes in v2:
> - moved the rxpktprocessed and rx_read_ptr increment after refiling the control
>   block
>
>  drivers/net/ethernet/broadcom/genet/bcmgenet.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index fff2634b6f34..fdc9ec09e453 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -1285,11 +1285,6 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_priv *priv,
>                 cb = &priv->rx_cbs[priv->rx_read_ptr];
>                 skb = cb->skb;
>
> -               rxpktprocessed++;
> -
> -               priv->rx_read_ptr++;
> -               priv->rx_read_ptr &= (priv->num_rx_bds - 1);
> -
>                 /* We do not have a backing SKB, so we do not have a
>                  * corresponding DMA mapping for this incoming packet since
>                  * bcmgenet_rx_refill always either has both skb and mapping or
> @@ -1404,6 +1399,10 @@ refill:
>                 err = bcmgenet_rx_refill(priv, cb);
>                 if (err)
>                         netif_err(priv, rx_err, dev, "Rx refill failed\n");
> +
> +               rxpktprocessed++;
> +               priv->rx_read_ptr++;
> +               priv->rx_read_ptr &= (priv->num_rx_bds - 1);
>         }
>
>         return rxpktprocessed;
> --
> 1.9.1
>
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