Re: [PATCH net 1/8] net: enetc: fix the off-by-one issue in enetc_map_tx_buffs()

[Michal Swiatkowski <michal.swiatkowski@linux.intel.com>]

On Mon, Feb 17, 2025 at 05:38:59PM +0800, Wei Fang wrote:
> When the DMA mapping error occurs, it will attempt to free 'count + 1'
> tx_swbd instead of 'count', so fix this off-by-one issue.
> 
> Fixes: d4fd0404c1c9 ("enetc: Introduce basic PF and VF ENETC ethernet drivers")
> Cc: stable@vger.kernel.org
> Signed-off-by: Wei Fang <wei.fang@nxp.com>
> ---
>  drivers/net/ethernet/freescale/enetc/enetc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
> index 6a6fc819dfde..f7bc2fc33a76 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> @@ -372,13 +372,13 @@ static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
>  dma_err:
>  	dev_err(tx_ring->dev, "DMA map error");
>  
> -	do {
> +	while (count--) {
>  		tx_swbd = &tx_ring->tx_swbd[i];
>  		enetc_free_tx_frame(tx_ring, tx_swbd);
>  		if (i == 0)
>  			i = tx_ring->bd_count;
>  		i--;
> -	} while (count--);
> +	};

In enetc_lso_hw_offload() this is fixed by --count instead of changing
to while and count--, maybe follow this scheme, or event better call
helper function to fix in one place.

The same problem is probably in enetc_map_tx_tso_buffs().

Thanks
Michal

>  
>  	return 0;
>  }
> -- 
> 2.34.1
>