Subject: Re: [PATCH v2 net 9/9] net: enetc: fix the off-by-one issue in enetc_map_tx_tso_buffs()

From: Michal Swiatkowski <[email-masked]>
Date: Wed, 19 Feb 2025 12:04:14 +0100

On Wed, Feb 19, 2025 at 01:42:47PM +0800, Wei Fang wrote:
> There is an off-by-one issue for the err_chained_bd path, it will free
> one more tx_swbd than expected. But there is no such issue for the
> err_map_data path. To fix this off-by-one issue and make the two error
> handling consistent, the loop condition of error handling is modified
> and the 'count++' operation is moved before enetc_map_tx_tso_data().
> 
> Fixes: fb8629e2cbfc ("net: enetc: add support for software TSO")
> Cc: [email-masked]
> Signed-off-by: Wei Fang <[email-masked]>
> ---
>  drivers/net/ethernet/freescale/enetc/enetc.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
> index 9a24d1176479..fe3967268a19 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> @@ -832,6 +832,7 @@ static int enetc_map_tx_tso_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb
>  			txbd = ENETC_TXBD(*tx_ring, i);
>  			tx_swbd = &tx_ring->tx_swbd[i];
>  			prefetchw(txbd);
> +			count++;
>  
>  			/* Compute the checksum over this segment of data and
>  			 * add it to the csum already computed (over the L4
> @@ -848,7 +849,6 @@ static int enetc_map_tx_tso_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb
>  				goto err_map_data;
>  
>  			data_len -= size;
> -			count++;
>  			bd_data_num++;
>  			tso_build_data(skb, &tso, size);
>  
> @@ -874,13 +874,13 @@ static int enetc_map_tx_tso_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb
>  	dev_err(tx_ring->dev, "DMA map error");
>  
>  err_chained_bd:
> -	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--);
> +	}
>  
>  	return 0;
>  }

Thanks for fixing it.
Reviewed-by: Michal Swiatkowski <[email-masked]>

> -- 
> 2.34.1