Re: [PATCH iwl-net] idpf: fix RSS LUT memcpy size

[Jacob Keller <jacob.e.keller@intel.com>]

On 4/29/2026 12:42 AM, Larysa Zaremba wrote:
> Based on the following feedback from Sashiko (received for iXD phase 1
> patchset, but valid for the net tree):
> 
>  "Is the bounds check xn_params.recv_mem.iov_len < lut_buf_size sufficient?
>   Since lut_buf_size only represents the size of the array elements, should
>   this check instead verify that the payload is at least
>   sizeof(struct virtchnl2_rss_lut) + lut_buf_size?
> 
>   [...]
> 
>   Does memcpy copy the correct amount of data here? rss_lut_size stores the
>   number of 32-bit entries, not the size in bytes. Should it use
>   lut_buf_size or rss_data->rss_lut_size * sizeof(u32) instead?"
> 
> After inspecting the code, it was concluded that RSS memcpy size is in fact
> 4 times smaller than it has to be, since a single array entry in a u32, and
> rss_data->rss_lut_size is clearly used as an array size. Required Rx buffer
> size is also too small, but this is a common issue in the idpf code.
> 
> Use a full buffer size (lut_buf_size) instead of the array length
> (rss_data->rss_lut_size) when doing memcpy of RSS lookup table.
> While at it, increase required Rx buffer size to a whole flex-array
> containing structure instead of just the array.
> 
> Link: https://sashiko.dev/#/patchset/20260323174052.5355-1-larysa.zaremba%40intel.com?part=8
> Fixes: 95af467d9a4e ("idpf: configure resources for RX queues")
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
> Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
> ---
>  drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
> index be66f9b2e101..a97d2e9b54d4 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
> +++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
> @@ -2916,7 +2916,7 @@ int idpf_send_get_set_rss_lut_msg(struct idpf_adapter *adapter,
>  		return -EIO;
>  
>  	lut_buf_size = le16_to_cpu(recv_rl->lut_entries) * sizeof(u32);
> -	if (reply_sz < lut_buf_size)
> +	if (reply_sz < lut_buf_size + sizeof(struct virtchnl2_rss_lut))

This feels like it should be using struct_size or flex_array_size...

>  		return -EIO;
>  
>  	/* size didn't change, we can reuse existing lut buf */
> @@ -2933,7 +2933,7 @@ int idpf_send_get_set_rss_lut_msg(struct idpf_adapter *adapter,
>  	}
>  
>  do_memcpy:
> -	memcpy(rss_data->rss_lut, recv_rl->lut, rss_data->rss_lut_size);
> +	memcpy(rss_data->rss_lut, recv_rl->lut, lut_buf_size);
>  
>  	return 0;
>  }