Subject: Re: [PATCH net v2] i40e/i40evf: proper update of the page_offset field

From: Mauro Rodrigues <[email-masked]>
Date: Mon, 15 May 2017 09:45:52 -0300

On Mon, May 15, 2017 at 06:52:00AM +0200, Björn Töpel wrote:
> From: Björn Töpel <[email-masked]>
> 
> In f8b45b74cc62 ("i40e/i40evf: Use build_skb to build frames")
> i40e_build_skb updates the page_offset field with an incorrect offset,
> which can lead to data corruption. This patch updates page_offset
> correctly, by properly setting truesize.
> 
> Note that the bug only appears on architectures where PAGE_SIZE is
> 8192 or larger.
> 
> Fixes: f8b45b74cc62 ("i40e/i40evf: Use build_skb to build frames")
> Signed-off-by: Björn Töpel <[email-masked]>

I tested the fix and it solves the problem for me! Thank you!

> ---
>  drivers/net/ethernet/intel/i40e/i40e_txrx.c   | 3 ++-
>  drivers/net/ethernet/intel/i40evf/i40e_txrx.c | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> index 29321a6167a6..cd894f4023b1 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
> @@ -1854,7 +1854,8 @@ static struct sk_buff *i40e_build_skb(struct i40e_ring *rx_ring,
>  #if (PAGE_SIZE < 8192)
>  	unsigned int truesize = i40e_rx_pg_size(rx_ring) / 2;
>  #else
> -	unsigned int truesize = SKB_DATA_ALIGN(size);
> +	unsigned int truesize = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) +
> +				SKB_DATA_ALIGN(I40E_SKB_PAD + size);
>  #endif
>  	struct sk_buff *skb;
> 
> diff --git a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
> index dfe241a12ad0..12b02e530503 100644
> --- a/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
> +++ b/drivers/net/ethernet/intel/i40evf/i40e_txrx.c
> @@ -1190,7 +1190,8 @@ static struct sk_buff *i40e_build_skb(struct i40e_ring *rx_ring,
>  #if (PAGE_SIZE < 8192)
>  	unsigned int truesize = i40e_rx_pg_size(rx_ring) / 2;
>  #else
> -	unsigned int truesize = SKB_DATA_ALIGN(size);
> +	unsigned int truesize = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) +
> +				SKB_DATA_ALIGN(I40E_SKB_PAD + size);
>  #endif
>  	struct sk_buff *skb;
> 
> -- 
> 2.11.0
>