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

Jacob Keller
2026-04-30T16:38:54Z

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;
> }