Re: [PATCH net v3 2/2] octeon_ep_vf: fix skb frags overflow in the RX path

[Maciej Fijalkowski]

On Sat, Jul 04, 2026 at 02:15:11PM +0800, Maoyi Xie wrote:
> __octep_vf_oq_process_rx() has the same unbounded fragment loop as the PF
> driver. buff_info->len comes from the device response header, and one
> fragment is added per buffer_size chunk with no check against
> MAX_SKB_FRAGS. A long packet yields about 18 fragments, one past the
> default MAX_SKB_FRAGS of 17, so skb_add_rx_frag() writes past
> shinfo->frags[].
> 
> The fragment count is now checked before napi_build_skb(). A packet that
> needs more fragments than the skb can hold is dropped.
> octep_vf_oq_drop_rx() drains its descriptors. The napi_build_skb()
> failure path now uses the same helper.
> 
> Fixes: 1cd3b407977c ("octeon_ep_vf: add Tx/Rx processing and interrupt support")
> Co-developed-by: Kaixuan Li <kaixuan.li@xxxxxxxxxx>
> Signed-off-by: Kaixuan Li <kaixuan.li@xxxxxxxxxx>
> Signed-off-by: Maoyi Xie <maoyixie.tju@xxxxxxxxx>

Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>

> ---
>  .../marvell/octeon_ep_vf/octep_vf_rx.c        | 46 ++++++++++++-------
>  1 file changed, 30 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_rx.c b/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_rx.c
> index d982474082..aa77b673ae 100644
> --- a/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_rx.c
> +++ b/drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_rx.c
> @@ -357,6 +357,29 @@ static inline u32 octep_vf_oq_next_idx(struct octep_vf_oq *oq, u32 idx)
>  	return (idx + 1 == oq->max_count) ? 0 : idx + 1;
>  }
>  
> +static void octep_vf_oq_drop_rx(struct octep_vf_oq *oq,
> +				struct octep_vf_rx_buffer *buff_info,
> +				u32 *read_idx, u32 *desc_used)
> +{
> +	u16 data_len = buff_info->len - oq->max_single_buffer_size;
> +
> +	(*desc_used)++;
> +	*read_idx = octep_vf_oq_next_idx(oq, *read_idx);
> +	while (data_len) {
> +		dma_unmap_page(oq->dev, oq->desc_ring[*read_idx].buffer_ptr,
> +			       PAGE_SIZE, DMA_FROM_DEVICE);
> +		buff_info = (struct octep_vf_rx_buffer *)
> +			    &oq->buff_info[*read_idx];
> +		buff_info->page = NULL;
> +		if (data_len < oq->buffer_size)
> +			data_len = 0;
> +		else
> +			data_len -= oq->buffer_size;
> +		(*desc_used)++;
> +		*read_idx = octep_vf_oq_next_idx(oq, *read_idx);
> +	}
> +}
> +
>  /**
>   * __octep_vf_oq_process_rx() - Process hardware Rx queue and push to stack.
>   *
> @@ -431,25 +454,16 @@ static int __octep_vf_oq_process_rx(struct octep_vf_device *oct,
>  			struct skb_shared_info *shinfo;
>  			u16 data_len;
>  
> +			data_len = buff_info->len - oq->max_single_buffer_size;
> +			if (DIV_ROUND_UP(data_len, oq->buffer_size) > MAX_SKB_FRAGS) {
> +				octep_vf_oq_drop_rx(oq, buff_info, &read_idx, &desc_used);
> +				continue;
> +			}
> +
>  			skb = napi_build_skb((void *)resp_hw, PAGE_SIZE);
>  			if (!skb) {
>  				oq->stats->alloc_failures++;
> -				desc_used++;
> -				read_idx = octep_vf_oq_next_idx(oq, read_idx);
> -				data_len = buff_info->len - oq->max_single_buffer_size;
> -				while (data_len) {
> -					dma_unmap_page(oq->dev, oq->desc_ring[read_idx].buffer_ptr,
> -						       PAGE_SIZE, DMA_FROM_DEVICE);
> -					buff_info = (struct octep_vf_rx_buffer *)
> -						    &oq->buff_info[read_idx];
> -					buff_info->page = NULL;
> -					if (data_len < oq->buffer_size)
> -						data_len = 0;
> -					else
> -						data_len -= oq->buffer_size;
> -					desc_used++;
> -					read_idx = octep_vf_oq_next_idx(oq, read_idx);
> -				}
> +				octep_vf_oq_drop_rx(oq, buff_info, &read_idx, &desc_used);
>  				continue;
>  			}
>  			rx_bytes += buff_info->len;
> -- 
> 2.34.1
>