Re: [PATCH net v3] net: xilinx: axienet: Fix IRQ coalescing packet count overflow

[Sean Anderson <sean.anderson@linux.dev>]

On 1/9/25 17:42, Sean Anderson wrote:
> If coalece_count is greater than 255 it will not fit in the register and
> will overflow. This can be reproduced by running
> 
>     # ethtool -C ethX rx-frames 256
> 
> which will result in a timeout of 0us instead. Fix this by checking for
> invalid values and reporting an error.
> 
> Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
> Fixes: 8a3b7a252dca ("drivers/net/ethernet/xilinx: added Xilinx AXI Ethernet driver")
> ---
> 
> Changes in v3:
> - Validate and reject instead of silently clamping
> 
> Changes in v2:
> - Use FIELD_MAX to extract the max value from the mask
> - Expand the commit message with an example on how to reproduce this
>   issue
> 
>  drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> index 0f4b02fe6f85..c2991aeccf2b 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> @@ -2056,6 +2056,12 @@ axienet_ethtools_set_coalesce(struct net_device *ndev,
>  		return -EBUSY;
>  	}
>  
> +	if (ecoalesce->rx_max_coalesced_frames > 255 ||
> +	    ecoalesce->rx_max_coalesced_frames > 255) {

The second line should be for tx and not rx.

Will resend tomorrow if no other feedback.

--Sean

> +		NL_SET_ERR_MSG(extack, "frames must be less than 256");
> +		return -EINVAL;
> +	}
> +
>  	if (ecoalesce->rx_max_coalesced_frames)
>  		lp->coalesce_count_rx = ecoalesce->rx_max_coalesced_frames;
>  	if (ecoalesce->rx_coalesce_usecs)